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Last Updated :2024/10/19

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Master

Affiliation (Master)

  • Faculty of Fisheries Sciences　Marine Bioresource and Environmental Science　Marine Environmental Science

Affiliation (Master)

  • Faculty of Fisheries Sciences　Marine Bioresource and Environmental Science　Marine Environmental Science

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Profile and Settings

Degree

  • Master of Science（1995/12 The University of Tokyo）
  • Doctor of Agriculture（1991/03 The University of Tokyo）

Profile and Settings

  • Name (Japanese)

    Kasai

  • Name (Kana)

    Akihide

  • Name

    200901097375482411

Alternate Names

Achievement

Research Interests

  • numerical simulation   environmental DNA   stable isotope analysis   沿岸海洋学   水産海洋学   Coastal Oceanography   Fisheries Oceanography   

Research Areas

  • Life sciences / Aquaculture
  • Natural sciences / Atmospheric and hydrospheric science
  • Environmental science/Agricultural science / Environmental dynamics

Research Experience

  • 2015/04 - Today Hokkaido Univeristy Faculty of Fisheries Sciences Professor
  • 2013/04 - 2015/03 Kyoto University Field Science Education and Research Center
  • 2004/02 - 2013/03 Kyoto University
  • 1994/04 - 2004/01 Kyoto University Faculty of Agriculture
  • 1997 - 1998 ウェールズ大学バンガー校海洋学部 特別研究員

Education

  • 1989/04 - 1994/03  The University of Tokyo  Graduate School of Science
  • 1985/04 - 1989/03  気象大学校

Committee Memberships

  • 2022 - Today   Environmental DNA society   Vice president
  • 2021 - Today   Hokkaido Prefecture   Hokkaido Environmental Impact Review Board
  • 2020 - Today   The eDNA Society   Administrator

Awards

  • 2024/03 The Japanese Society of Fisheries Science Award of Excellence for a Scientific Paper
     The effect of temperature on environmental DNA degradation of Japanese eel 
    受賞者: Kasai A, Takada S, Yamazaki A, Masuda R and Yamanaka H
  • 2022/03 日本水産学会 Award of Excellence for a Scientific Paper
     Dispersion and degradation of environmental DNA from caged fish in a marine environment 
    受賞者: Murakami H;Yoon S;Kasai A;Minamoto T;Yamamoto S;Sakata MK;Horiuchi T;Sawada H;Kondoh M;Yamashita Y;Masuda R
  • 2017/03 Japanese Society of Fisheries Oceanography Best paper award of Japanese Society of Fisheries Oceanography
     Relative contribution of estuarine nursery areas to the adult population of the temperate seabass Lateolabrax japonicus in the Tango Sea, as revealed by otolith Sr:Ca ratios 
    受賞者: Fuji Taiki;Kasai Akihide;Ueno Masahiro;Yamashita Yoh
  • 2015/03 水産海洋学会 宇田賞
     沿岸域の物質循環と生物生産機構に関する研究 
    受賞者: 笠井 亮秀
  • 2012/03 日本水産学会 水産学進歩賞
     沿岸生態系における流動環境と物質循環に関する研究 
    受賞者: 笠井 亮秀
  • 2010 水産海洋学会 2010年度水産海洋学会論文賞
     夏季の有明海筑後川の高濁度汽水域における粒状有機物の動態 
    受賞者: 鈴木啓太・杉本亮・笠井亮秀・小路淳・中山耕至・田中克
  • 2008/03 日本水産学会 論文賞
     Transport and survival processes of eggs and larvae of jackmackerel Trachurus japonicus in the East China Sea 
    受賞者: 笠井 亮秀
  • 2007 日本水産学会 Best paper award of the Japanese Society of Fisheries Science
     Cellulose digestion by common Japanese freshwater clam Corbicula japonica 
    受賞者: Sakamoto K;Touhata K;Yamashita M;Kasai A;Toyohara H
  • 2007 水産海洋学会 2007年度水産海洋学会論文賞
     春季の有明海筑後川の高濁度汽水域における粒状有機物の動態 
    受賞者: 鈴木啓太;杉本亮;笠井亮秀;小路淳;中山耕至;田中克
  • 2006/03 日本水産学会 論文賞
     Food sources for the bivalve Corbicula japonica in the foremost fishing lakes estimated from stable isotope analysis 
    受賞者: 笠井 亮秀
  • 2002/03 水産海洋学会 水産海洋学会論文賞
     伊勢湾の流動構造と貧酸素水塊

Published Papers

  • Michio Kondoh, Minoru Kasada, Takuzo Abe, Akihide Kasai, Akihiro Dazai, Reiji Masuda, Satoquo Seino, Shota Suzuki, Yukari Suzuki-Ohno, Akifumi S. Tanabe
    Ecological Research Monographs 83 - 99 2191-0707 2024/06/25
  • Takuma Yonago, Tatsuya Kawakami, Akihide Kasai
    Journal of Fish Biology 104 (5) 1468 - 1482 0022-1112 2024/02/18 [Refereed][Not invited]
     
    Abstract Environmental DNA (eDNA) is a promising tool for the continuous monitoring of fish ecology and diversity. However, its potential for describing the phenological activity of fish has rarely been examined. This study aimed to elucidate a linkage between the spatiotemporal distribution of eDNA and the phenology of an amphidromous fish, ayu Plecoglossus altivelis altivelis, in a river in Hokkaido, Japan, which is its northernmost distributional area. A significant positive correlation between eDNA concentration and catch per unit effort of P. a. altivelis in the river confirmed the use of eDNA as a surrogate for the abundance of P. a. altivelis. eDNA of P. a. altivelis was first detected in late April on a sandy beach adjacent to the river mouth. Subsequent to its first detection at the lowest site in the river in early May, eDNA spread throughout the river, indicating the upstream migration of P. a. altivelis. Spawning activity was also represented by a rapid increase in eDNA concentration and its surge at night in the lowest reaches of the river during September and October. These results suggest that upstream migration and spawning primarily commenced when the water temperature reached 10°C and decreased below 20°C, respectively. This observation is consistent with the behavioral responses observed in P. a. altivelis populations from other regions of Japan. Consequently, this study demonstrated that eDNA distribution was closely linked to the phenological activity of P. a. altivelis and that eDNA is a powerful tool for studying the phenology of migratory fishes.
  • Daiki NOMURA, Ryota AKINO, Matthew CORKILL, Keizo HIRANO, Akihide KASAI, Seiji KATAKURA, Yusuke KAWAGUCHI, Tatsuya KAWAKAMI, Riri KIMURA, Delphine LANNUZEL, Ryosuke MAKABE, Mirai MATSUURA, Kohei MATSUNO, Klaus MEINERS, Keizo NAGASAKI, Yuichi NOSAKA, Nana SAMORI, Shinnosuke SAKAYA, Eun Yae SON, Ryotaro SUGA, Yumi SUNAKAWA, Keigo D. TAKAHASHI, Masaharu TAKAHASHI, Yuka TAKEDA, Takenobu TOYOTA, Manami TOZAWA, Pat WONGPAN, Hiroshi YOSHIDA, Kazuhiro YOSHIDA, Masaki YOSHIMURA
    Bulletin of Glaciological Research 42 19 - 37 1345-3807 2024
  • Yukari Suzuki‐Ohno, Akifumi S. Tanabe, Akihide Kasai, Reiji Masuda, Satoquo Seino, Akihiro Dazai, Shota Suzuki, Takuzo Abe, Michio Kondoh
    Environmental DNA 2637-4943 2023/04/18 [Refereed]
  • Tatsuya Kawakami, Aya Yamazaki, Maki Asami, Yuko Goto, Hiroki Yamanaka, Susumu Hyodo, Hiromichi Ueno, Akihide Kasai
    Ecology and Evolution 13 (3) 2045-7758 2023/03/24 [Refereed]
  • Tatsuro Karaki, Kei Sakamoto, Goro Yamanaka, Shingo Kimura, Akihide Kasai
    Fisheries Oceanography 1054-6006 2023/03/20 [Refereed]
  • Tatsuya Kawakami, Aya Yamazaki, Hai Chao Jiang, Hiromichi Ueno, Akihide Kasai
    Frontiers in Marine Science 10 2023 
    Ongoing warming and sea-ice reductions in the Arctic can seriously impact cold-water species, such as polar cod (Boreogadus saida), necessitating biomonitoring to reveal the ecological consequences. Recent methodological advancements in environmental DNA (eDNA) techniques have increased our ability to conduct ecological monitoring at various locations, including the Arctic. This study aimed to provide an overview of the distribution of polar cod across the Bering and Chukchi Seas by employing species-specific detection of eDNA. First, we successfully developed novel species-specific qPCR assay targeting the mitochondrial D-loop region, which exclusively amplifies eDNA derived from polar cod. Subsequently, polar cod eDNA was detected using the assay from the samples that we collected latitudinally across the study area during the open-water season. Polar cod eDNA was primarily detected in the surface water from the central Chukchi Sea shelf and the northernmost observation line (75°N), which was located on the shelf slope, off the Point Barrow, and in the marginal ice zone. In contrast, only trace amounts of eDNA were detected in the Bering Sea. This pattern corresponded well with the distribution of water masses classified based on environmental conditions. The detection of eDNA in surface water was clearly limited to cold (-1 to 5°C) and low salinity (25–32) water, whereas it was detected in a higher salinity range (32–34) in the middle and bottom layers. These findings are consistent with current knowledge about the distribution and habitat of the polar cod, suggesting that eDNA can be regarded as a reliable tool to replace or supplement conventional methods. Incorporating eDNA techniques into large-scale oceanographic surveys can improve the spatial and temporal resolution of fish species detection with a reasonable sampling effort and will facilitate the continuous monitoring of Arctic ecosystems.
  • Sachihiko Itoh, Aigo Takeshige, Akihide Kasai, Shingo Kimura, Jun Hayakawa, Naoya Ohtsuchi
    Reference Module in Earth Systems and Environmental Sciences 2023 [Refereed]
  • Yosuke Amano, Tsuguo Otake, Hiroyuki Togashi, Toshihiro Wada, Akihide Kasai, Yoshikazu Kato, Chikage Yoshimizu, Ichiro Tayasu, Yutaka Kurita, Kotaro Shirai
    Estuarine, Coastal and Shelf Science 277 108028 - 108028 0272-7714 2022/10 [Refereed]
  • 弘章 村上, 錫鎭 尹, 亮秀 笠井, 利文 源, 哲史 山本, 雅之 坂田, 智矢 堀内, 英樹 澤田, 倫生 近藤, 洋 山下, 玲爾 益田
    NIPPON SUISAN GAKKAISHI 88 (4) 206 - 206 0021-5392 2022/07/15 [Refereed]
  • Daiki NOMURA, Hiroki IKAWA, Yusuke KAWAGUCHI, Naoya KANNA, Tatsuya KAWAKAMI, Yuichi NOSAKA, Sachi UMEZAWA, Manami TOZAWA, Takahito HORIKAWA, Reishi SAHASHI, Taichi NOSHIRO, Ibuki KABA, Makoto OZAKI, Fumiyoshi KONDO, Keisuke ONO, Itsuka S. YABE, Eun Yae SON, Takahiro TOYODA, Sohiko KAMEYAMA, Changqing WANG, Hajime OBATA, Atsushi OOKI, Hiromichi UENO, Akihide KASAI
    Bulletin of Glaciological Research 40 1 - 17 1345-3807 2022/04 [Refereed]
  • Edouard Lavergne, Manabu Kume, Hyojin Ahn, Yumi Henmi, Yuki Terashima, Feng Ye, Satoshi Kameyama, Yoshiaki Kai, Kohmei Kadowaki, Shiho Kobayashi, Yoh Yamashita, Akihide Kasai
    Conservation Biology 36 (3) 0888-8892 2021/12/02 [Refereed]
  • Yuka Karasawa, Hiromichi Ueno, Ryo Tanisugi, Ryo Dobashi, Seokjin Yoon, Akihide Kasai, Masashi Kiyota
    Technical Report (17) 1029-5917 2021/11/29 [Refereed]
  • Sayaka Takahashi, Shingo Takada, Hiroki Yamanaka, Reiji Masuda, Akihide Kasai
    PLOS ONE 16 (9) e0255576 - e0255576 2021/09/16 [Refereed]
     
    Environmental DNA (eDNA) analysis with species-specific primer/probe sets is promising as a tool to quantify fish abundance and distribution. Nevertheless, several factors could reduce the accuracy of this method. Here, we aimed to analyze whether intraspecific variability and diel activity rhythm affect eDNA detection in Japanese eels (Anguilla japonica). For this purpose, we performed tank experiments focusing on two points. First, we assessed the effects of base pair sequences with probe region polymorphism on eDNA detection. Next, we evaluated the influences of diel rhythm, activity, and individual differences in eDNA release rate on eDNA concentration. We examined the base pair sequences of the probe regions of 20 individuals and found genetic mismatches in two of them. The eDNA concentration was estimated to be much lower in these variants than it was in the other individuals. We conducted a rearing experiment on four non-variant individuals to explore the influences of diel activity and inter-individual differences in eDNA detection. Nocturnal eel activity was reflected in the eDNA detection but the inter-individual differences remained large. The observed weak positive correlations between eDNA concentration and activity suggest that eDNA emission is highly dependent on basal metabolism. The present study suggests that consideration of polymorphic sites at the probe region and diel activity rhythms should improve the accuracy and precision of abundance estimation through eDNA. Such fine-tuning is applicable not only for eels but also for other fishes to be targeted by eDNA technology.
  • Akihide Kasai, Aya Yamazaki, Hyojin Ahn, Hiroki Yamanaka, Satoshi Kameyama, Reiji Masuda, Nobuyuki Azuma, Shingo Kimura, Tatsuro Karaki, Yuko Kurokawa, Yoh Yamashita
    Frontiers in Ecology and Evolution 9 2021/02/25 [Refereed]
     
    The abundance of Japanese eel Anguilla japonica has rapidly decreased in recent decades. Following a re-evaluation of the possibility of extinction, the Japanese Ministry of the Environment and the International Union for Conservation of Nature listed the Japanese eel as an endangered species in 2013 and 2014, respectively. However, their abundance and precise distribution have never been clarified owing to their nocturnality and difficulty in their capture. In this study, the distribution of Japanese eels was investigated by monitoring for environmental DNA (eDNA), a non-invasive and efficient detection method. A total of 365 water samples were collected from 265 rivers located throughout Japan. High concentrations of eDNA of Japanese eels were detected in rivers on the Pacific side, but were low in the Sea of Japan side. In particular, very little eDNA amplification was confirmed from Hokkaido and the north of the Sea of Japan. The eDNA distribution in Japanese rivers coincides with the transport of the larvae in the ocean, as estimated by numerical simulations. Generalized linear mixed models were developed to explain the distribution of eDNA concentrations. The total nitrogen concentration emerged as an important factor in the best model. These results indicate that the distribution of Japanese eel is mostly determined by the maritime larval transport, and their survival and growth depend on the abundance of food in the river. The findings of the present study are useful for the management of populations and in the conservation of Japanese eels.
  • Watershed proportion of forest cover fostering the conservation of red-listed fish richness in estuaries
    Lavergne E, Kume M, Ahn H, Henmi Y, Terashima Y, Ye F, Kameyama S, Kai Y, Kadowaki K, Yamashita Y, Kasai A
    Conservation Biology 2021 [Refereed]
  • Traditional land use effects on nutrient export from watersheds to coastal seas
    Ryo Sugimoto, Akihide Kasai, Douglas R. Tait, Takahito Rihei, Takeru Hirai, Kazuyoshi Asai, Yuji Tamura, Yoh Yamashita
    Nutrient Cycling in Agroecosystems 2020/11/11 [Refereed]
  • Hyojin Ahn, Manabu Kume, Yuki Terashima, Feng Ye, Satoshi Kameyama, Masaki Miya, Yoh Yamashita, Akihide Kasai
    PLOS ONE 15 (10) e0231127 - e0231127 2020/10/06 [Refereed]
  • Toshifumi Minamoto, Masaki Miya, Tetsuya Sado, Satoquo Seino, Hideyuki Doi, Michio Kondoh, Keigo Nakamura, Teruhiko Takahara, Satoshi Yamamoto, Hiroki Yamanaka, Hitoshi Araki, Wataru Iwasaki, Akihide Kasai, Reiji Masuda, Kimiko Uchii
    Environmental DNA 3 (1) 8 - 13 2637-4943 2020/08/10 [Refereed][Not invited]
  • Keiichi Fukaya, Hiroaki Murakami, Seokjin Yoon, Kenji Minami, Yutaka Osada, Satoshi Yamamoto, Reiji Masuda, Akihide Kasai, Kazushi Miyashita, Toshifumi Minamoto, Michio Kondoh
    Molecular Ecology 30 (13) 3057 - 3067 0962-1083 2020/07/20 [Refereed]
  • Akihide Kasai, Shingo Takada, Aya Yamazaki, Reiji Masuda, Hiroki Yamanaka
    Fisheries Science 86 (3) 465 - 471 0919-9268 2020/05 [Refereed][Not invited]
  • Keita W. Suzuki, Taiki Fuji, Akihide Kasai, Sachihiko Itoh, Shingo Kimura, Yoh Yamashita
    Fisheries Oceanography 29 (1) 66 - 83 1054-6006 2020/01 [Refereed][Not invited]
  • Correlation of changes in seasonal distribution and catch of red sea bream Pagrus major with winter temperature in the eastern Seto Inland Sea, Japan (1972-2010)
    Yamamoto M, Omi H, Yasue N, Kasai A
    Fisheries Oceanography 29 1 - 9 2020 [Refereed][Not invited]
  • Kume M, Lavergne E, Ahn H, Terashima Y, Kadowaki K, Ye F, Kameyama S, Kai Y, Henmi Y, Yamashita Y, Kasai A
    Ecological Indicators 121 107216 - 107216 1470-160X 2020 [Refereed]
     
    © 2020 The Author(s) Estuarine and coastal ecosystems are important habitats for many fish species. Large-scale patterns of estuarine and coastal fish communities can be affected by geographical factors, such as water temperature and latitude, that limit or allow fish dispersal, and/or by environmental factors that select locally adapted species. Furthermore, increased human activity has also altered fish diversity by modifying estuarine/coastal environments. Here, we used environmental DNA metabarcoding to study a large-scale pattern of estuarine/coastal fish communities across 25 watersheds in the Japanese Archipelago, and we assessed the effects of geographical, environmental, and anthropogenic factors in structuring these communities. Of the 290 fish species detected, 47 species were red-listed by the Japanese Ministry of Environment, and nine were alien. Non-metric multidimensional scaling showed that latitude and water temperature affected both river-mouth and coastal-sea fish communities. Although other anthropogenic factors did not affect these communities, bank artificialisation rates influenced both. The relationship between each fish community and ocean currents was weak. The number of red-listed fish affected both fish community structures, whereas that of alien species did not. The numbers of red-listed fish in coastal points and of all fish species were negatively influenced to the human population density. These findings provide useful information that may be used to conserve estuarine and coastal ecosystems.
  • Karasawa Y, Ueno H, Tanisugi R, Dobashi R, Yoon S, Kasai A, Kiyota M
    Deep Sea Research Part II 175 104702 - 104702 0967-0645 2020 [Refereed][Not invited]
  • Hiroaki Murakami, Seokjin Yoon, Akihide Kasai, Toshifumi Minamoto, Satoshi Yamamoto, Masayuki K. Sakata, Tomoya Horiuchi, Hideki Sawada, Michio Kondoh, Yoh Yamashita, Reiji Masuda
    Fisheries Science 85 (2) 327 - 337 0919-9268 2019/03 [Refereed][Not invited]
  • Age determination and growth pattern of temperate seabass Lateolabrax japonicus
    Jiang W, Lavergne E, Kurita Y, Todate K, Kasai A, Fuji T, Yamashita Y
    Fisheries Science 85 81 - 98 2019 [Refereed][Not invited]
  • JIANG Wei, LAVERGNE Edouard, KURITA Yutaka, TODATE Kana, KASAI Akihide, FUJI Taiki, YAMASHITA Yoh
    FISHERIES SCIENCE 85 (1) 99 - 100 0919-9268 2019/01 [Refereed][Not invited]
  • Sachihiko Itoh, Aigo Takeshige, Akihide Kasai, Shingo Kimura
    Fisheries Science 84 (2) 293 - 307 1444-2906 2018/03/01 [Refereed][Not invited]
     
    To enhance numerical modeling of the coastal ecosystem complex (CEC), we reviewed the CEC and related concepts along with the current coastal ecosystem model framework in this study. We identified two model implementation paths from the initial objectives to numerical models: specific model building, and the use of existing model frameworks. As the CEC is still at the conceptual stage, both paths are possible. Four important ecological features of CEC modeling (population connectivity, habitat heterogeneity, ontogeny of organisms, and trophic interactions) were also identified. Models for population connectivity, species distributions, life histories, and food webs were categorized using these features. We found that some previously established concepts (between–habitat interactions, coastal ecosystem mosaic, and seascape nursery) overlap with the CEC concept. Several existing integrated model frameworks were reviewed, focusing on their potential to simulate CEC processes. Building specific models for the CEC at the current conceptual stage will be challenging, and modification of existing models will be needed if they are to be used for CEC modeling. Habitat function, ontogenetic development in early life stages, and recruitment variability are important factors when modifying existing models for the development of CEC models. Although model complexity should become high to reproduce observed ecoclogical processes, an intermediate level of model ccomplexity is feasible to decrease parameter uncertainty in models for fisheries management.
  • Taiki Fuji, Akihide Kasai, Yoh Yamashita
    Fisheries Science 84 (2) 163 - 172 1444-2906 2018/03/01 [Refereed][Not invited]
     
    Hydrographic conditions and distributions of juvenile temperate sea bass Lateolabrax japonicus were observed in early spring from 2009 to 2012 in the Yura River estuary, which is highly stratified due to its small tides and consequent seawater intrusion into the bottom layer of the river as a salt wedge. In all four studied years, the upstream expansion of their distribution coincided with the timing of the salt wedge intrusion from the lower to upper estuary, indicating that juvenile fish used salt wedge intrusions to ascend the estuary in early spring. However, juveniles sometimes remained in the nearshore area even when the salt wedge intrusion had already occurred, indicating that other triggers are also likely to be necessary. We therefore evaluated the effects of temperature on upstream migration behaviors. The relationship between the mean temperature they experienced from hatch until starting the ascent and mean age of each cohort at the upstream migration fitted with the law of effective cumulative temperature. Most cohorts ascended the river at an effective cumulative temperature of approximately 500 °C–days. This suggests that higher temperatures would lead to a shorter period prior to the upstream migration.
  • Akihide Kasai, Taiki Fuji, Keita W. Suzuki, Yoh Yamashita
    Fisheries Science 84 (2) 153 - 162 1444-2906 2018/03/01 [Refereed][Not invited]
     
    Partial migration describes intrapopulation variation in the migratory behavior, i.e. some individuals from a population migrate to low-salinity river areas, while others remain in coastal areas. This paper reviews the partial migration pattern of juvenile temperate seabass Lateolabrax japonicus, which is a migration pattern not commonly seen in Japan. Seabass spawn offshore, and eggs and larvae are transported to coastal areas. Some of these juveniles then ascend rivers, while others remain in coastal areas. Juveniles efficiently use physical structures in their habitat they use tidal currents to ascend rivers in macrotidal estuaries, while they use the salt wedge in microtidal estuaries. Once juveniles ascend the river, they can feed on the abundant prey and attain more rapid growth than those remaining in coastal areas. As estuaries are highly productive areas, they play significant roles as nurseries for juveniles of various fishes. However, compared with coastal areas, the relative area of estuaries is considerably smaller and its environmental conditions are more variable. For example, nearly 40% of adult seabass in Tango Bay were estimated to use estuarine areas as a nursery, while the other 60% use coastal areas during their juvenile stage. Using both estuaries and coastal areas through partial migration during the juvenile stage is concluded to contribute to the stabilization and yield of seabass populations.
  • Mami Harada, Manabu Kume, Noritaka Mochioka, Yuji Tamura, Toko Kanzaki, Shunya Hashiguchi, Akihide Kasai, Yoh Yamashita
    Nippon Suisan Gakkaishi (Japanese Edition) 84 (1) 45 - 53 1349-998X 2018 [Refereed][Not invited]
     
    Local people in Oita Prefecture perform a traditional fishery called the Ishi-kura fishing method in estuaries. Ishi-kura is an underwater pile of approximately 0.5 tons of stones 15-30 cm in diameter, and wild eels dwell inside the pile and are caught using nets.We examined the relationship between Japanese eel Anguilla japonica and aquatic animals caught with an Ishi-kura net which was modified for aquatic animal research, in the Iroha and Katsura Rivers, Oita Prefecture, Japan. Based on community structure analysis, the aquatic animal community in the Ishi-kura net consisting of 54 taxonomic animals was divided into two groups by distance from the river month and substrate the upstream group mainly contained the genus Hemigrapsus and genus Batillaria, and the downstream one predominantly contained Macrobrachium nipponense and Clithon retropicta. Based on stomach content analysis, 39 out of 79 eels consumed the same aquatic animal groups found in Ishi-kura. However, eels inhabiting downstream mainly preyed on mud shrimp, and those inhabiting upstream predominantly fed on crab, suggesting that eels may not use Ishi-kura for feeding but for living space. These findings suggest that Ishi-kura nets may be useful for monitoring eels as well as aquatic animals as their potential prey items.
  • Seokjin Yoon, Akihide Kasai
    ESTUARINE COASTAL AND SHELF SCIENCE 198 225 - 235 0272-7714 2017/11 [Refereed][Not invited]
     
    The dominant external forcing factors influencing estuarine circulation differ among coastal environments. A three-dimensional regional circulation model was developed to estimate external influence indices and relative contributions of external forcing factors such as external oceanic forcing, surface heat flux, wind stress, and river discharge to circulation and hydrographic properties in Tango Bay, Japan. Model results show that in Tango Bay, where the Tsushima Warm Current passes offshore of the bay, under conditions of strong seasonal winds and river discharge, the water temperature and salinity are strongly influenced by surface heat flux and river discharge in the surface layer, respectively, while in the middle and bottom layers both are mainly controlled by open boundary conditions. The estuarine circulation is comparably influenced by all external forcing factors, the strong current, surface heat flux, wind stress, and river discharge. However, the influence degree of each forcing factor varies with temporal variations in external forcing factors as: the influence of open boundary conditions is higher in spring and early summer when the stronger current passes offshore of the bay, that of surface heat flux reflects the absolute value of surface heat flux, that of wind stress is higher in late fall and winter due to strong seasonal winds, and that of river discharge is higher in early spring due to snow-melting and summer and early fall due to flood events. (C) 2017 Elsevier Ltd. All rights reserved.
  • Numerical simulation on distribution of environmental DNA of Japanese jack mackerel (Trachurusjaponicus) in a semi-closed bay
    Seokjin Yoon, Akihide Kasai, Satoshi Yamamoto, Kenji Minami, Kazushi Miyashita, Reiji Matsuda, Michio Kondoh
    한국수산과학회 양식분과 학술대회 126 - 126 2017/05 [Refereed][Not invited]
  • Food composition for blue mussels (Mytilus edulis) in the Menai Strait, UK, based on physical and biochemical analyses
    Morioka H, Kasai A, Miyake Y, Kitagawa T, Kimura S
    Journal of Shellfish Research 36 659 - 668 2017 [Refereed][Not invited]
  • Yuji Tamura, Ryo Sugimoto, Akihide Kasai, Hisashi Yokoyama, Yoh Yamashita
    NIPPON SUISAN GAKKAISHI 83 (6) 1017 - 1017 0021-5392 2017 [Refereed][Not invited]
  • Yoh Yamashita, Akihide Kasai, Takayuki Shiraiwa, Yoshihisa Shirayama
    NIPPON SUISAN GAKKAISHI 83 (6) 1008 - 1008 0021-5392 2017 [Refereed][Not invited]
  • Kenta Watanabe, Akihide Kasai, Koji Fukuzaki, Masahiro Ueno, Yoh Yamashita
    ESTUARINE COASTAL AND SHELF SCIENCE 184 126 - 137 0272-7714 2017/01 [Refereed][Not invited]
     
    We investigated interactions among seasonal fluctuations in phytoplankton biomass, riverine nutrient flux, and the fluxes of nutrients entrained by estuarine circulation in Tango Bay, Japan, to determine the influence of freshwater inflows to an open bay on coastal phytoplankton productivity. The riverine nutrient flux was strongly regulated by river discharge. Estuarine circulation was driven by river discharge, with high fluxes of nutrients (mean nitrate + nitrite flux: 5.3 +/- 3.5 Mg [mega grams]-N day(-1)) between winter and early spring, enhanced by nutrient supply to the surface water via vertical mixing. In contrast, low-nutrient seawater was delivered to the bay between late spring and summer (1.0 0.8 Mg N, day(-1)). Seasonal fluctuations in phytoplanlcton biomass were affected by the entrained fluxes of oceanic nutrients and variation in the euphotic zone depth, and to a lesser degree by the riverine nutrient flux. Bioassays and stoichiometric analyses indicated that phytoplankton growth was limited by nitrogen and/or phosphorus. Both the entrainment of oceanic nutrients and the euphotic zone depth affected the duration and magnitude of blooms. Our findings show that, unlike semi-enclosed bays, seasonal variations in coastal phytoplankton in an open coastal system are primarily fueled by the entrainment of oceanic nutrients and are influenced by both freshwater inflow and coastal conditions (e.g. vertical mixing and wind events). (C) 2016 Elsevier Ltd. All rights reserved.
  • Mitsuo Yamamoto, Dan Liu, Akihide Kasai, Kei Okubo, Masaru Tanaka
    REGIONAL STUDIES IN MARINE SCIENCE 8 89 - 98 2352-4855 2016/11 [Refereed][Not invited]
     
    Iron (Fe) dynamics in the Chikugo River were investigated in order to understand the relationship between the characteristics of Fe concentrations in the basin and the river estuarine ecosystem and that of the inner area of the Ariake Sea. Analysis of Fe concentration from monthly samples at 29 sites in the Chikugo River from July 2011 to May 2012 was conducted together with analyses of nitrogen (N) and phosphate (P) concentrations. Fe concentration changed slightly from the upstream to the middle basin, whereas in the estuary it increased sharply at 15 km from the river mouth and decreased again near the river mouth. This trend is different from the trends for N and P concentrations, and the Fe distribution was distinctive throughout the year. Further investigation was conducted focusing on the Fe dynamics in the estuary and the inner Ariake Sea. It was found that the trend of Fe concentration corresponds to the trend of turbidity in the estuary. The reasons of the characteristic Fe dynamics are suggested that supplied Fe is accumulated by the scavenging effect of particulate organic matter in the estuarine turbidity maximum to form floccules. As these particle materials are important for forming the ecosystem in the inner Ariake Sea, it is suggested that Fe dynamics have an influence in forming the ecosystem in the Chikugo River and the Ariake Sea. (C) 2016 Elsevier B.V. All rights reserved.
  • Sachihiko Itoh, Akihide Kasai, Aigo Takeshige, Kei Zenimoto, Shingo Kimura, Keita W. Suzuki, Yoichi Miyake, Tatsuhiro Funahashi, Yoh Yamashita, Yoshiro Watanabe
    JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 121 (8) 6331 - 6350 2169-9275 2016/08 [Refereed][Not invited]
     
    Mooring and hydrographic surveys were conducted in Tango Bay, a microtidal region of freshwater influence (ROFI) in the Sea of Japan, in order to clarify the circulation pattern in the bay and its driving forces. Monthly mean velocity records at four stations revealed an inflow and outflow at the eastern and northern openings of the bay, respectively, indicating an anticyclonic circulation across the bay mouth. The circulation was significantly intensified in winter, in accordance with the prevailing NW wind component of the winter monsoon. The anticyclonic circulation at the bay mouth was connected to an estuarine circulation that was evident near the mouth of the Yura River at the bay head. Surface salinity just offshore of the river mouth was closely related to the Yura River discharge, whereas in lower layers the offshore water had a stronger influence on salinity. Prior to a seasonal increase in the Yura River discharge, summer salinity decreased markedly through the water column in Tango Bay, possibly reflecting intrusion of the Changjiang Diluted Water transported by the Tsushima Warm Current. In contrast with the traditional assumption that estuarine circulation is controlled mainly by river discharge and tidal forcing, the circulation in Tango Bay is strongly influenced by seasonal wind and the Tsushima Warm Current. The narrow shelf may be responsible for the strong influence of the Tsushima Warm Current on circulation and water exchange processes in Tango Bay.
  • Taiki Fuji, Akihide Kasai, Masahiro Ueno, Yoh Yamashita
    ESTUARIES AND COASTS 39 (4) 1208 - 1220 1559-2723 2016/07 [Refereed][Not invited]
     
    The feeding ecology of juvenile temperate seabass (Lateolabrax japonicus) in relation to various prey environments was analyzed in the Yura River estuary from 2008 to 2012. Juveniles mainly fed on copepods and mysids, both in the Yura River estuary and in the adjacent coastal area. The dependency on the mysids increased as juveniles grew from 15 to 25 mm standard length (SL), and the main stomach contents were mysids for juveniles larger than 25 mm SL. The maximum size of food contents increased from 2 to 15 mm with the growth of juveniles from 15 to 25 mm SL. Most prey items smaller and larger than 2 mm were composed of copepods and mysids, respectively. The mean size of ingested food items increased with the size of the juveniles, while the mean number of prey items in each stomach decreased with growth after juveniles reached 22 mm SL. As a result, the stomach content index increased with the size of juveniles. These results indicate that the shift to larger-sized prey items (from copepods to mysids) is important for juveniles to obtain energy efficiently. Mysids were larger and more abundant in the estuaries than those in the coastal area. Therefore, the estuary provided better foraging conditions to juvenile temperate seabass than the coastal area.
  • Taiki Fuji, Akihide Kasai, Masahiro Ueno, Yoh Yamashita
    FISHERIES OCEANOGRAPHY 25 (4) 448 - 456 1054-6006 2016/07 [Refereed][Not invited]
     
    Otolith Sr:Ca ratios were used to evaluate the contribution of estuarine nursery areas to the temperate seabass (Lateolabrax japonicus) population in Tango Bay, the Sea of Japan. Otolith Sr:Ca ratios of juveniles collected from freshwater, brackish and coastal areas were analysed to determine a criterion for distinguishing whether individuals used estuarine or coastal areas as nurseries. Otolith Sr:Ca ratios of adult seabass collected around Tango Bay were also analysed to detect the records of salinity that juveniles experienced and to estimate the contribution of each habitat. Sr:Ca ratios of the edges of otoliths of juveniles from freshwater areas were 2.4x10(-3) in average, which were significantly lower than those of juveniles collected from a coastal area (4.9x10(-3) in average) owing to differences in salinity conditions among these areas. Based on the threshold criterion determined by this difference, 39 out of 107 (36%) adult seabass were estimated to have used the estuary as a nursery during their juvenile stage according to their Sr:Ca chronologies. Despite the small area covered by estuarine nurseries compared with coastal waters, the Yura River estuary contributed considerably to the adult seabass population. This indicates estuaries play an important role as nurseries for seabass juveniles, and it should be noted that the estuaries are important nurseries to conserve the stocks of coastal fishes.
  • Akihide Kasai, Daisuke Ishizaki, Takane Isoda
    FISHERIES SCIENCE 82 (3) 491 - 498 0919-9268 2016/05 [Refereed][Not invited]
     
    Diet-switch experiments with three different species of microalgae were conducted to estimate diet-tissue isotopic fractionation of carbon (C) and nitrogen (N) isotopes in the freshwater clam Corbicula sandai. The delta C-13 and delta N-15 values in the soft tissues of C. sandai changed in each experiment, with little inter-individual deviations, thereby reflecting the switch in diet. Isotope values of the clam reached the asymptotic value at around 40 days after the switch. Equilibrium isotopic signatures, as well as turnovers of carbon and nitrogen in the whole soft tissues, were estimated by exponential decay models. Fractionations for C. sandai varied from 0.1 to 0.7 aEuro degrees for carbon, and from 2.1 to 3.6 aEuro degrees for nitrogen; these values fell within or were close to the range of previously accepted fractionation values (0-1 aEuro degrees for carbon and 3-4 aEuro degrees for nitrogen). The half-life values for carbon in the bivalves (12-22 days) were about twofold longer than those for nitrogen (7-9 days). The specific fractionation values estimated in this study contribute towards improving our understanding of inter-specific trophic relationships and aquatic food webs.
  • Ryo Sugimoto, Akihide Kasai
    BIOGEOCHEMISTRY 128 (1-2) 1 - 17 0168-2563 2016/03 [Refereed][Not invited]
     
    Isotope analysis of dissolved inorganic nitrogen (DIN) and a mixing model along the salinity gradient were used to clarify the dominant biogeochemical processes controlling nutrient dynamics within a shallow eutrophic estuary in Japan. Although delivery of riverine DIN into the estuary is largely dominated by mixing with seawater during most months, internal biogeochemical processes of DIN assimilation by phytoplankton and DIN production by remineralization and subsequent nitrification within the estuary offer the most reasonable explanation for observed deviations in the isotopic compositions of NO3- from mixing behavior. However, the balance of each process changed over time. During phytoplankton blooming in summer, co-occurrence of NO3- assimilation and NO3- regeneration inhibited the accumulation of NO3- within the estuary. Moreover, assimilation of NH4+ as well as NO3- by phytoplankton complicates the nutrient dynamics within the estuary. However, mostly conservative or productive behavior of DIN as well as PO43- showed that recycled nutrients are significant net source within the estuary. These results suggest recycled nutrients within the estuary could have a non-negligible impact on eutrophication in Osaka Bay.
  • Minamoto Toshifumi, Yamamoto Satoshi, Kasai Akihide, Kondoh Michio
    Bulletin on Coastal Oceanography 日本海洋学会 沿岸海洋研究会 53 (2) 173 - 178 1342-2758 2016 [Refereed][Not invited]
     
    Distribution survey methods of macro-organisms using environmental DNA（eDNA）have been rapidly developing in recent years. Environmental DNA analysis can be divided into two major methods, species-specific detection and eDNA metabarcoding. Here we outline these techniques, and we report the preliminary results of an eDNA-based biomass survey of Japanese jack mackere（l Trachurus japonicus）. The results showed significantly positive associations between eDNA concentrations from water samples and echo intensity detected by an echo sounder, suggesting that the spatial variation of the eDNA concentration can reflect the local biomass of fish even in marine environments. More detailed distribut ion mapping of coastal fish can be achieved by environmental DNA analysis, and it will contribute in various fields, such as fisheries science, ichthyology, and ecology.
  • Sangdeok Chung, Hirokazu Suzaki, Akihide Kasai, Hideaki Nakata
    ESTUARIES AND COASTS 38 (4) 1365 - 1375 1559-2723 2015/07 [Refereed][Not invited]
     
    Variations in the fish community structure in Omura Bay, an enclosed bay in the East China Sea, were investigated using long-term fishery landing data over the past five decades (1965-2006). We confirmed that the fish community structure in Omura Bay showed three conspicuous regimes during the study period. Anchovies dominated in the pelagic domain with abundant and various demersal fish species in the first phase (1965-1978). Demersal fish declined remarkably with the dominance of sardines in the pelagic domain during the second phase (1979-1987), and the fish community was simplified with the return of anchovies and no recovery of demersal fish in the third phase (1988-2006). These changes were significantly related with periodic large-scale climate changes and cumulative regional-scale human impacts. The replacement of sardine/anchovy caused by a climate regime shift in the North Pacific contributed to the fish community regime shifts in Omura Bay. Moreover, habitat degradation such as depletion of dissolved oxygen combined with climate-induced changes in food web systems resulted in a rapid reduction in demersal fish. Contraction of the habitat volume due to an increase in oxygen-restricted water simplified the fish community structure and eventually reduced fishery landings in Omura Bay. These findings demonstrate that long-term fish community responses to large-scale climate changes and regional-scale human impacts can be observed in a coastal enclosed bay, providing useful information for fisheries management in areas with climate and human-induced changes.
  • Taiki Fuji, Akihide Kasai, Masahiro Ueno, Yoh Yamashita
    ENVIRONMENTAL BIOLOGY OF FISHES 97 (11) 1221 - 1232 0378-1909 2014/11 [Refereed][Not invited]
     
    It is important to know the characteristics of migration pattern and vital rates of juveniles to understand the early life history and its effect on the population dynamics of fishes. The relationship between growth and migration pattern of juvenile temperate seabass Lateolabrax japonicus in the Yura River estuary was examined by combination of stable carbon isotope ratio (delta C-13) and otolith microstructure. Gut fullness indices were also examined to know the feeding condition of juveniles. delta C-13 values of seabass juveniles in the lower estuary and surf zone (LES) were enriched, while those in freshwater zone (FW) were depleted, consistent with delta C-13 differences in prey items. The back-calculated growth rates of juveniles in FW were significantly lower than those of juveniles that resided in the LES from 50 days to 90 days old, implying that juveniles with poor growth ascended the river while those with better growth remained in the LES. However, the growth rates of the juveniles, which resided in FW for more than 1 month, caught up with and even overtook those of juveniles in LES within 1 month after ascended the river. The higher water temperature and better feeding conditions would contribute to better growth rates of juveniles in FW than those in LES.
  • Kenta Watanabe, Akihide Kasai, Emily S. Antonio, Kentaro Suzuki, Masahiro Ueno, Yoh Yamashita
    ESTUARINE COASTAL AND SHELF SCIENCE 139 67 - 77 0272-7714 2014/02 [Refereed][Not invited]
     
    To examine the influence of salt-wedge intrusion on ecological processes at lower trophic levels in estuaries, we investigated seasonal variability in the nutrients, phytoplankton biomass (chlorophyll a), zooplankton density, and composition in the Yura Estuary, Japan. Phytoplankton composition was determined under two discriminative regimes: salt-wedge regime (summer) and freshwater regime (winter). Phytoplankton from two groups bloomed simultaneously under the salt-wedge regime. Freshwater and brackish phytoplankton dominated the upper freshwater layer (similar to 16,100 cells mL(-1)) while marine phytoplankton were dominant below the halocline (similar to 12,200 cells mL(-1)). Both phytoplankton groups grew using riverine nutrients. Marine phytoplankton increased closer to the tip of the salt-wedge, indicating that marine phytoplankton grew in situ in the river. The residence time of salt water increased due to the low river discharge from spring to summer, enhancing mineralization in the salt-wedge. Regenerated nutrients in the salt-wedge contribute to subsequent marine phytoplankton blooms. Copepods were more abundant in the salt-wedge (similar to 80.9 ind. L-1) than in the upper freshwater layer ( similar to 142 ind. L-1) during summer. Phytoplankton and zooplankton densities under the freshwater regime (winter; similar to 360 cells mL(-1), similar to 39.7 ind. L-1) were lower than under the salt-wedge regime (summer). The high river discharge under the freshwater regime flushes out the salt-wedge and discourages biological production in the river. Our results showed that salt-wedge intrusions change the physical conditions and nutrient dynamics, enhancing biological production in the salt-wedge estuary. (C) 2014 The Authors. Published by Elsevier Ltd. All rights reserved.
  • KASAI Akihide
    Aqua-Bio Science Monographs Terrapub 7 (4) 117 - 145 1882-3203 2014 [Refereed][Not invited]
  • 杉本 亮, 笠井 亮秀, 佐藤 専寿
    沿岸海洋研究 = Bulletin on coastal oceanography 日本海洋学会沿岸海洋研究部会 51 (1) 19 - 28 1342-2758 2013/08 [Refereed][Not invited]
  • Matiss Zagars, Kou Ikejima, Akihide Kasai, Nobuaki Arai, Prasert Tongnunui
    ESTUARINE COASTAL AND SHELF SCIENCE 119 145 - 152 0272-7714 2013/03 [Refereed][Not invited]
     
    Mangrove production has been found to make a major contribution to the nutrition of a fish community in the Sikao Creek mangrove estuary, Southwest Thailand. Gut content analysis and carbon and nitrogen stable isotope analysis were used to assess fish feeding behavior and trophic reliance on different primary producers (mangrove leaves, phytoplankton, microphytobenthos) focusing on 19 dominant fish species, and 4 potential fish food items. Cluster analysis identified 5 trophic groups and the IsoSource model indicated the importance of primary food sources in trophically supporting different fish species. Most analyzed fish species had carbon isotopic signatures that were more depleted than those reported in previous studies, and the IsoSource model indicated that mangrove leaves were an important primary food source. This may be a specific characteristic of our study site, which is not well connected to other productive coastal habitats that provide alternative primary food sources. Thus we suggest that food chains in trophically isolated mangrove estuaries of southwest Thailand are more dependent on mangrove tree production. We also assessed the relationship of individuality in fish feeding habits and variability of delta C-13 values and showed that several mangrove fish species have significant intraspecies variability in feeding habits, possibly due to high intraspecific competition. (C) 2013 Elsevier Ltd. All rights reserved.
  • Effects of short time variation in the river discharge on the salt wedge intrusion in the Yura Estuary, a micro tidal estuary, Japan
    Funahashi T, Kasai A, Ueno M, Yamashita Y
    Journal of Water Resource and Protection, 5, 343-348. 2013 [Refereed][Not invited]
  • River ascending mechanisms of juvenile seabass
    Taiki Fuji, Akihide Kasai, Masahiro Ueno, Yoh Yamashita
    Proceedings of the 10th Global Congress on ICM: Lessons Learned to Address New Challenges, EMECS 2013 - MEDCOAST 2013 Joint Conference 1 581 - 590 2013 
    Recent surveys have revealed that juvenile temperate seabass, Lateolabrax japonicus, migrate into upper estuaries in early spring. However, their mechanisms for river ascent are insufficiently understood. In order to clarify these mechanisms, hydrographic conditions and juvenile distribution were observed in early spring from 2009 to 2012 in the Yura River estuary, which is highly stratified due to its small tidal variations and consequent seawater intrusion into the bottom layer of the river as a salt wedge. The timing and distance of salt-wedge intrusion are mainly controlled by river discharge. In all four studied years, juveniles first ascended the river to the middle estuary 4-6 km upstream from the river mouth. Subsequently, they reached the upper estuary, 11-15 km from the river mouth, within one month. The expansion of their distribution coincided with the timing of salt-wedge intrusion from the mid- to upper estuary. This indicates that the distribution of juveniles is dependent on the extent of the seawater intrusion into the bottom layer in early spring. However, juveniles sometimes remained in the nearshore area even when the salt-wedge intrusion had already occurred, indicating that salt-wedge intrusion is only one necessary condition, and that there is likely another trigger for ascent. The effects of temperature on river ascent behaviours were evaluated. There was a significant negative relationship between the mean age of seabass juveniles at the time of river ascent and the mean temperature they experienced from birth until starting the ascent. Most juveniles ascended the river at an effective cumulative temperature of approximately 500 C. This suggests that juveniles need to reach a cumulative temperature threshold in order to start ascending the river, and higher temperatures would lead to a shorter preparation period for river ascent. It is considered that high temperatures would lead to a short period for the metamorphosis of juveniles. Metamorphosis enables seabass to adjust to environments of different salinities.
  • Emily S. Antonio, Akihide Kasai, Masahiro Ueno, Yuka Ishihi, Hisashi Yokoyama, Yoh Yamashita
    ESTUARINE COASTAL AND SHELF SCIENCE 112 86 - 97 0272-7714 2012/10 [Refereed][Not invited]
     
    We investigated the fluctuations of carbon and nitrogen stable isotope ratios in benthic consumers and their potential food sources to determine the spatial and temporal variations in the utilization of available organic matter, indicating the origin and pathways of energy from Yura Estuary to Tango Sea, Japan. Field samplings were conducted from the upper estuary to offshore with sampling frequency of twice per season from April (spring) 2006 to February (winter) 2007. The delta C-13 signatures of the upper and lower estuary benthos showed depleted and in wide range (-28.9 parts per thousand to -13.5 parts per thousand) compared to the enriched and within narrow range signatures of marine benthos (-20.6 parts per thousand to -14.0 parts per thousand) in all seasons. On the contrary, the delta N-15 signatures of benthic communities showed decreasing trend seaward and summer values were different from the other seasons. Using the dual isotope and multisource mixing models, we estimated the relative contributions of potential food sources to the benthos diet. River POM played an important source of energy for the estuarine benthos, especially in winter when river discharge was high. Marine POM served as an important alternative food for the estuarine benthos from spring to autumn when seawater intruded the bottom estuary. Benthic microalgae were the major food source at the shallow coast throughout the year, while marine POM fueled the deep coast and offshore benthic food webs. Spatial and temporal feeding variations in estuarine benthic communities were driven by the hydrology of the estuary, whereas primary production and transport of food source dictated diet variations of marine benthic communities. The elucidation of the dynamic energy subsidy among aquatic systems highlights the importance of the land sea transition zones that is crucial for benthic secondary productions. (C) 2011 Elsevier Ltd. All rights reserved.
  • Keita W. Suzuki, Akihide Kasai, Kouji Nakayama, Masaru Tanaka
    JOURNAL OF OCEANOGRAPHY 68 (3) 453 - 471 0916-8370 2012/06 [Refereed][Not invited]
     
    The inner part of the Ariake Sea is one of the most productive estuarine systems in Japan. To examine potential food items for estuarine organisms, we conducted monthly observations of the dynamics of particulate organic matter along the macrotidal Chikugo River estuary in 2005 and 2006. In the neighboring macrotidal Midori and Kuma River estuaries, comparative observations were made. High turbidity and strong vertical mixing were observed only at low salinities (<10) in the Chikugo River estuary. In contrast, the Midori and Kuma River estuaries were characterized by less turbid and less mixed waters. Concentrations of particulate organic carbon often exceeded 5 mg l(-1) in or close to the estuarine turbidity maximum (ETM) of the Chikugo River estuary. However, such high concentrations were rarely observed in the other two estuaries. The observed differences could be attributable to different hydrodynamic processes related to the different lengths of tidal reaches: 23, 8, and 6 km in the Chikugo, Midori, and Kuma Rivers, respectively. In the Chikugo River estuary, spatiotemporal changes of chlorophyll a suggested that phytoplankton occurred abundantly up- and/or downstream from the ETM especially during the warm season. In contrast, pheophytin (i.e., plant detritus) always accumulated in or close to the ETM. Carbon stable isotope ratios and carbon to nitrogen ratios indicated that the plant detritus was derived from phytoplankton and terrestrial plants. The Chikugo River estuary has a high potential to support the production of estuarine organisms through abundant plant detritus in the well-developed ETM all the year round.
  • Akihide Kasai
    NIPPON SUISAN GAKKAISHI 78 (3) 372 - 375 0021-5392 2012/05 [Not refereed][Not invited]
  • 小型魚類の生体内元素分析を用いたダム下流域における急激な物質循環変化の検証
    東信行, 村元寛子, 伊藤結美, 河野冬樹, 野田香織, 笠井亮秀, 渡邉泉
    河川技術論文集, 18, 405-410. 2012 [Refereed][Not invited]
  • Emily S. Antonio, Akihide Kasai, Masahiro Ueno, Yuka Ishihi, Hisashi Yokoyama, Yoh Yamashita
    JOURNAL OF CRUSTACEAN BIOLOGY 31 (4) 635 - 646 0278-0372 2011/10 [Refereed][Not invited]
     
    Spatial and temporal variations in the diet of Crangon uritai were examined using stable isotope and stomach content analyses. The sand shrimp and its potential prey were collected from Yura Estuary (3-5 m), shallow coast (5-10 m), and deep coast (30-60 m) stations of Tango Sea from April 2006 to February 2007. The measurements of the length (carapace and total lengths) and feeding habit (stomach content and stable isotope ratios) of C. uritai showed that this shrimp changed its diet during migrations between the estuary and marine environments. This species consumes a variety of food at the lower estuary: mysid Orientomysis japonica, small crustaceans particularly amphipod Melita hoshinoi, and bivalve Veremolpa micra. The abundant mysid O. japonica at the shallow coast and juveniles of unidentified bivalve species at the deep coast were the favored food throughout the year. The delta C-13 and delta N-15 variations in C. uritai confirmed the spatial and temporal diet shift in gut content composition as the sand shrimp grow and migrate along the estuary-marine gradient.
  • Emily S. Antonio, Akihide Kasai, Masahiro Ueno, Yuka Ishihi, Hisashi Yokoyama, Yoh Yamashita
    JOURNAL OF CRUSTACEAN BIOLOGY 31 (4) 635 - 646 0278-0372 2011/10 [Refereed][Not invited]
     
    Spatial and temporal variations in the diet of Crangon uritai were examined using stable isotope and stomach content analyses. The sand shrimp and its potential prey were collected from Yura Estuary (3-5 m), shallow coast (5-10 m), and deep coast (30-60 m) stations of Tango Sea from April 2006 to February 2007. The measurements of the length (carapace and total lengths) and feeding habit (stomach content and stable isotope ratios) of C. uritai showed that this shrimp changed its diet during migrations between the estuary and marine environments. This species consumes a variety of food at the lower estuary: mysid Orientomysis japonica, small crustaceans particularly amphipod Melita hoshinoi, and bivalve Veremolpa micra. The abundant mysid O. japonica at the shallow coast and juveniles of unidentified bivalve species at the deep coast were the favored food throughout the year. The delta C-13 and delta N-15 variations in C. uritai confirmed the spatial and temporal diet shift in gut content composition as the sand shrimp grow and migrate along the estuary-marine gradient.
  • Yasuhiro Kamimura, Akihide Kasai, Jun Shoji
    AQUATIC ECOLOGY 45 (3) 367 - 376 1386-2588 2011/09 [Refereed][Not invited]
     
    The economic value of ecosystem services of vegetated habitats (seagrass and macroalgal beds) has been estimated to be among the highest of the various ecosystems on earth. However, fish production has not been included in the evaluations due to the difficulty of quantitative estimation of fish production in the field. In the present study, annual production and economic value of wild juvenile black rockfish, Sebastes cheni, a dominant fish species in seagrass and macroalgal beds in the central Seto Inland Sea were estimated. Juvenile S. cheni migrated into vegetated habitats at about 20 mm total length (TL) and grew up to about 60 mm TL by late May. Juvenile abundance was highest in April (2007) or March (2008). Eight cohorts with the same extrusion period (each cohort covering a 10-day period) were identified using otolith daily increments. The annual estimates of S. cheni juvenile production were 13,080 g ha(-1) year(-1) in 2007 and 18,360 g (-1) year(-1) in 2008. Based on the unit price of artificially raised S. cheni juveniles, the economic value of the annual wild juvenile production was converted to 654,000 JPY (Japanese yen: 100 JPY = ca. 1 USD) ha(-1) year(-1) for 2007 and 918,000 JPY ha(-1) year(-1) for 2008. Analyses of stomach contents and stable isotope (delta(13)C or delta(15)N) showed that juvenile S. cheni were highly dependent on copepods. The planktonic trophic pathway originating from phytoplankton supports the majority of the juvenile black rockfish production during the post-migration period (20-60 mm TL) in the seagrass and macroalgal beds through the production of copepod zooplankton. The total economic value of the ecosystem services of the vegetated habitat is suggested to be much higher than estimates in previous studies if the provisioning and regulating services which originate from fish production were included in the estimates.
  • T. Fuji, A. Kasai, K. W. Suzuki, M. Ueno, Y. Yamashita
    JOURNAL OF FISH BIOLOGY 78 (7) 2010 - 2025 0022-1112 2011/06 [Refereed][Not invited]
     
    The migration pattern of juvenile temperate seabass Lateolabrax japonicus in the stratified estuary of the Yura River was examined using carbon stable-isotope ratios (delta(13)C). delta(13)C values of mysids, which are the most important prey items for this species, were consistently enriched in the lower estuary and surf zone (LES), while depleted in the freshwater zone (FW). delta(13)C values of juveniles in LES were enriched, while those in FW were depleted, consistent with the delta(13)C difference in prey items. The results of delta(13)C showed that many juveniles migrated upstream from April to June and most of them stayed in FW until at least July. Juveniles that stayed in FW and LES for a relatively longer period (> c. 20 days) showed higher condition factors than those that stayed in FW for a short period (several days). This indicates that residence in FW enabled juveniles to achieve as good a body condition as residence in LES. (C) 2011 The Authors Journal of Fish Biology (C) 2011 The Fisheries Society of the British Isles
  • Ryo Sugimoto, Akihide Kasai, Kouichi Fujita, Kenichi Sakaguchi, Tomomi Mizuno
    JOURNAL OF OCEANOGRAPHY 67 (2) 231 - 240 0916-8370 2011/04 [Refereed][Not invited]
     
    Concentrations of particulate organic nitrogen (PN), dissolved inorganic nitrogen (DIN), and their nitrogen isotope ratios (delta (15)N) in the Kiso-Sansen Rivers were determined from monthly observations over the course of a year to assess variations in the form and sources of riverine nitrogen discharged into Ise Bay. The delta (15)N values of NO(3) (-) observed in the Kiso-Sansen Rivers showed a logarithmic decreasing trend from 8 to 0aEuro degrees, which varied with the river discharge, indicating mixing between point sources with high delta (15)N and non-point sources with low delta (15)N. The influence of isotope fractionation of in situ biogeochemical processes (mainly DIN assimilation by phytoplankton) on delta (15)N of NO(3) (-) was negligible, because sufficient concentrations of NH(4) (+) for phytoplankton demand would inhibit the assimilation of NO(3) (-). A simple relationship between river discharge and delta (15)N of NO(3) (-) showed that the fraction of total NO(3) (-) flux arising from point sources increased from 4.0-6.3% (1.1-1.8 tN day(-1)) during higher discharge (> 600 m(3) s(-1)) to 30.2-48.3% (2.6-4.1 tN day(-1)) during lower discharge (< 300 m(3) s(-1)). Riverine NO(3) (-) discharge from the Kiso-Sansen Rivers can explain 75% of the variations in surface NO(3) (-) at the head of Ise Bay over the year.
  • 菅原 達也, 荒井 修亮, 農原 治彦, 吉田 天士, 左子 芳彦, 笠井 亮秀, 吉永 郁生, 荒井 修亮, 藤原 建紀, 山下 洋, 益田 玲爾, 澤山 茂樹, 木下 政人, 鰺坂 哲朗
    日本水産學會誌 = Bulletin of the Japanese Society of Scientific Fisheries The Japanese Society of Fisheries Science 77 (1) 147 - 149 0021-5392 2011/01/15
  • Migration ecology of juvenile temperate seabass Lateolabrax japonicus in the Yura River estuary: A carbon stable isotope approach
    Fuji T, Kasai A, Suzuki K, Ueno M, Yamashita Y
    Journal of Fish Biology, 78, 2010-2025 2011 [Refereed][Not invited]
  • Taiki Fuji, Akihide Kasai, Keita W. Suzuki, Masahiro Ueno, Yoh Yamashita
    FISHERIES SCIENCE 76 (4) 643 - 652 0919-9268 2010/07 [Refereed][Not invited]
     
    Juvenile temperate seabass Lateolabrax japonicus were sampled along the Yura River estuary from April to July 2008 to determine their distribution and feeding habits during migration within a microtidal estuary. Throughout the sampling period, juvenile seabass were distributed not only in the surf zone, but also in the freshwater zone, and they were particularly abundant in areas with aquatic vegetation in the freshwater zone. This distribution pattern suggests that the early life history of the temperate seabass depends more intensively on the river (freshwater) than previously considered. Small juveniles in the freshwater zone fed on copepods and chironomid larvae and upon reaching a standard length (SL) of approximately 20 mm did they fed on mysids. In contrast, juveniles (approx. 17-80 mm SL) in the surf zone fed mainly on mysids.
  • Jun Shoji, Takaya Kudoh, Hideyuki Takatsuji, Osamu Kawaguchi, Akihide Kasai
    ESTUARINE COASTAL AND SHELF SCIENCE 86 (3) 485 - 490 0272-7714 2010/02 [Refereed][Not invited]
     
    Biological and physical surveys were conducted in order to investigate the relationship between environmental conditions and the distribution of moon jellyfish Aurelia aurita in Hiroshima Bay, western Seto Inland Sea, Japan. Moon jellyfish and ichthyoplankton were collected at 13 stations in Hiroshima Bay during monthly surveys from July to September in 2006 and 2007. Surface temperature in 2006 was significantly lower during the August and September cruises and surface salinity was lower during all cruises than in 2007. Moon jellyfish was the most dominant gelatinous plankton collected, accounting for 89.7% in wet weight. Mean moon jellyfish abundance in 2006 was higher than that in 2007 from July through September, with significant inter-year differences for July and September. Variability in precipitation and nutritional input from the Ohta River, northernmost part of Hiroshima Bay, were suggested as possible factors affecting the inter-annual variability in moon jellyfish abundance in the coastal areas of northern Hiroshima Bay. Moon jellyfish were more abundant in the coastal areas of northern Hiroshima Bay, where the dissolved oxygen (DO) concentration was lower, while low in the central part of the bay. Japanese anchovy Engraulis japonicus eggs were most dominant (58.1% in number) among the ichthyoplankton and were abundant in the central area of Hiroshima Bay. Explanatory analysis was conducted to detect possible effects of environmental conditions on the abundance of moon jellyfish and Japanese anchovy eggs during the summer months in Hiroshima Bay. Of the environmental conditions tested (temperature, salinity and DO of surface and bottom layers at each sampling station), bottom DO had the most significant effect on the moon jellyfish abundance: there was a negative correlation between the bottom DO and the moon jellyfish abundance in Hiroshima Bay during summer. (C) 2009 Elsevier Ltd. All rights reserved.
  • Ryo Sugimoto, Akihide Kasai, Toshihiro Miyajima, Kouichi Fujita
    ESTUARINE COASTAL AND SHELF SCIENCE 86 (3) 450 - 466 0272-7714 2010/02 [Refereed][Not invited]
     
    An important aspect of the nitrogen cycle in coastal environments concerns the source of the nitrogen used in primary production. Phytoplankton production in Ise Bay, one of the most eutrophic embayments in Japan, is supported by external nitrogen derived from rivers and the ocean, and regenerated nitrogen formed in hypoxic water within the bay. We evaluated the contribution of each source of dissolved inorganic nitrogen (DIN) to phytoplankton production in Ise Bay. A unique three-dimensional ecosystem model including nitrogen isotopes (delta N-15) was developed based on precise observations. Model results revealed that DIN (=ammonium + nitrate) consumption by phytoplankton exceeds the DIN supply from the rivers and ocean, indicating that a large amount of phytoplankton production in Ise Bay depends on regenerated DIN within the bay rather than on newly supplied DIN. However, the ratio of consumption to external supply differs seasonally. Distributions of simulated delta N-15 clearly showed the source of nitrogen incorporated by phytoplankton in each Source. The intrusion depth of oceanic water changes from the bottom to the middle layer in spring. Oceanic nitrate is transported into the euphotic layer by the middle layer intrusion and stimulates phytoplankton production at the bay mouth. The subsurface chlorophyll maximum layer then develops. In autumn, however, the intrusion depth of oceanic water changes from the middle layer to the bottom layer. Regenerated NO3-, which is accumulated in the hypoxic water mass, is uplifted and continuously supplied to the euphotic layer. These results imply that phytoplankton production in Ise Bay is mainly dominated by the internal cycle rather than the external supply. (C) 2009 Elsevier Ltd. All rights reserved.
  • Akihide Kasai, Yoshiro Kurikawa, Masahiro Ueno, Dominique Robert, Yoh Yamashita
    ESTUARINE COASTAL AND SHELF SCIENCE 86 (3) 408 - 414 0272-7714 2010/02 [Refereed][Not invited]
     
    We monitored hydrographic and biological conditions in the Yura Estuary and its coastal area from April 2006 to March 2008. Hydrographic conditions changed seasonally, and were mainly determined by river discharge and sea level, with tides playing a minor role. In summer, when river discharge was low and sea level was high, a salt-wedge regime was established until similar to 18 km upstream from the river mouth. Seawater intrusion into the river was however restricted in winter, when the river discharge was high and sea level was low. Water stratification caused by the seawater intrusion played an important role in phytoplankton dynamics. Phytoplankton developed in the middle layer of the estuary utilizing riverine nutrients, corresponding to the seawater intrusion into the bottom layer in summer. In winter, however, the phytoplankton production remained low in both estuary and sea. (C) 2009 Elsevier Ltd. All rights reserved.
  • Emily S. Antonio, Akihide Kasai, Masahiro Ueno, Yoshiro Kurikawa, Kanako Tsuchiya, Haruhiko Toyohara, Yuka Ishihi, Hisashi Yokoyama, Yoh Yamashita
    ESTUARINE COASTAL AND SHELF SCIENCE 86 (3) 401 - 407 0272-7714 2010/02 [Refereed][Not invited]
     
    We examined the feeding niche of four species of molluscs by analysis of their stable isotope signatures and cellulase activities to determine if they could utilize terrestrial organic matter. The molluscs and potential food sources were collected from the upper, middle and lower estuary of the Yura River from spring 2007 to winter 2008. All species showed positive cellulase activity which highlighted their potential to digest terrestrial organic matter. Consumption and assimilation of terrestrial organic matter by estuarine molluscs however varied spatially and temporally, reflecting species-specific differences in feeding niche and in response to variations in food availability in the estuary. Thus, terrestrial primary production in the catchment area supports secondary production of molluscs in the Yura River estuary. (C) 2009 Elsevier Ltd. All rights reserved.
  • Emily S. Antonio, Akihide Kasai, Masahiro Ueno, Nam-il Won, Yuka Ishihi, Hisashi Yokoyama, Yoh Yamashita
    ESTUARINE COASTAL AND SHELF SCIENCE 86 (1) 107 - 117 0272-7714 2010/01 [Refereed][Not invited]
     
    We investigated the distribution of PC and delta N-15 of organic matter among benthic communities from the upper estuary of Yura River to offshore of Tango Sea, Japan, to determine spatial variation in utilization of organic matter by benthic communities. The delta C-13 values of benthic animals ranged from -27 to -15 parts per thousand in the upper estuary, -21 to -15 parts per thousand in the lower estuary, -20 to -16 parts per thousand in the shallow coast (5-10 m depths), -18 to -16 parts per thousand in the deep coast (30-60 m depths) and -19 to -15 parts per thousand in offshore (100-150 m depths) stations. Adapting the dual isotope values to mixing models, we estimated the relative contributions of potential food sources to the benthos diet. Phytoplankton and macroalgae that intruded the estuary in summer were utilized as alternative food aside from the terrestrial-origin organic matter assimilated by the estuarine benthic consumers. Resuspended benthic microalgae were important source of energy in the shallow coastal stations, while abundant supply of phytodetritus fueled the deep coastal and offshore benthic food webs. Spatial difference in the diet of benthic communities depends largely on the shifts in the primary carbon source. Thus, benthic communities are important link of autochthonous/allochthonous production and secondary production in the continuous river-estuary-marine system. (C) 2009 Elsevier Ltd. All rights reserved.
  • Ryo Sugimoto, Akihide Kasai, Toshihiro Miyajima, Kouichi Fujita
    ESTUARINE COASTAL AND SHELF SCIENCE 85 (2) 231 - 240 0272-7714 2009/11 [Refereed][Not invited]
     
    Seasonal changes in the nitrogen stable isotope ratio of NO(3)(-) (delta(15)N(NO3)) were investigated in a temperate eutrophic coastal embayment in Japan. Wide variation of delta(15)N(NO3), from -10.4 to 9.3 parts per thousand was found along with changes in temperature, dissolved oxygen concentrations, and the composition of the dissolved inorganic nitrogen (DIN) pool. Throughout the year,delta(15)N(NO3), showed positive exponential and linear relationships with NO(3)(-) concentrations and fractions, respectively. The minima of delta(15)N(NO3) were observed in spring and autumn when the NO(3)(-) fraction in DIN was small, while the maximum was in summer when the NO(3)(-) fraction was large. These results indicate that nitrification was the dominant process that determined delta(15)N(NO3) variation. The delta(15)N(NO3) minima in spring and autumn suggested that hydrographic properties, such as low water temperature and short residence time of the water, suppressed the nitrifying bacterial activity in these seasons. An apparent nitrogen isotope discrimination (epsilon(nit)) by nitrification was estimated as -15 to -25 parts per thousand, which is similar to or slightly higher than previous laboratory estimates of marine nitrifiers. Furthermore, isotope results at the bay center over a year suggest that most of the NO(3)(-) was regenerated by in situ nitrification in the water-column. This implies that large amounts of regenerated nitrogen would lead the eutrophication in Ise Bay. (C) 2009 Elsevier Ltd. All rights reserved.
  • 鈴木 啓太, 杉本 亮, 笠井 亮秀, 中山 耕至, 田中 克
    水産海洋研究 73 (3) 149 - 160 2009/08/28 [Refereed][Not invited]
  • Ryo Sugimoto, Akihide Kasai, Toshihiro Miyajima, Kouichi Fujita
    CONTINENTAL SHELF RESEARCH 29 (14) 1678 - 1688 0278-4343 2009/07 [Refereed][Not invited]
     
    Hydrographic and biogeochemical observations were conducted along the longitudinal section from Ise Bay to the continental margin (southern coast of Japan) to investigate changes according to the Kuroshio path variations during the summer. The strength of the uplift of the cold deep water was influenced by the surface intrusion of the Kuroshio water to the shelf region. When the intrusion of the Kuroshio surface water to the shelf region was weak in 2006, the cold and NO(3)(-)-rich shelf water intruded into the bottom layer in the bay from the shelf This bottom intrusion was intensified by the large river discharge. The nitrogen isotope ratio (delta(15)N) of NO(3)(-)(4-5 parts per thousand) in the bottom bay water was same as that in the deeper NO(3)(-) over the shelf, indicating the supply of new nitrogen to the bay. The warm and NO(3)(-)-poor shelf water intruded into the middle layer via the mixing region at the bay mouth when the Kuroshio water distributed in the coastal areas off Ise Bay in 2005. The regenerated NO(3)(-) with isotopically light nitrogen (delta(15)N = -1 parts per thousand) was supplied from the shelf to the bay. This NO(3)(-) is regenerated by the nitrification in the upper layer over the shelf. The contribution rate of regenerated NO(3)(-) over the shelf to the total NO(3)(-) in the subsurface chlorophyll maximum layer in the bay was estimated at similar to 56% by a two-source mixing model coupled with the Rayleigh equation. (C) 2009 Elsevier Ltd. All rights reserved.
  • Ryo Sugimoto, Akihide Kasai, Toshihiro Miyajima, Kouichi Fujita
    CONTINENTAL SHELF RESEARCH 29 (10) 1303 - 1309 0278-4343 2009/05 [Refereed][Not invited]
     
    To clarify the sources and transformation of NO(3)(-) on the Pacific coast of Japan, observations over the continental shelf were conducted during the summer in 2005 and 2006 when the Kuroshio flowed close to and away from the coastal area, respectively. Below the halocline, there are two prominent salinity peaks that originated in two different waters. In the subsurface layer, the salinity maximum (S(max)) was indicative of the Kuroshio Water (KW), while the salinity minimum (S(min)) in the middle layer at similar to 400 m depth was indicative of the North Pacific Intermediate Water (NPIW). delta(15)N(NO3) ranged from 4.1 parts per thousand to 5.1 parts per thousand with a mean of 4.8 +/- 0.4 parts per thousand in the deeper water around S(min). Below 50m depth over the shelf break, delta(15)N(NO3) values (3.1 +/- 0.8 parts per thousand in 2005 and 4.6 +/- 0.3 parts per thousand in 2006) clearly increased as contribution of NPIW increased in 2006. On the contrary, subsurface delta(15)N of NO(3)(-) values (-1.1 +/- 0.1 parts per thousand) remained unchanged in both years, although the contribution of the KW to the subsurface water changed significantly. This Suggests that the source of NOT has little effect on the delta(15)N of NO(3)(-) in this layer. The negative delta(15)N values also coincided with the base of the chlorophyll maximum layer suggesting that these isotopic signals must be evidence of active nitrification in the upper layer. (C) 2009 Elsevier Ltd. All rights reserved.
  • Keita W. Suzuki, Akihide Kasai, Takane Isoda, Kouji Nakayama, Masaru Tanaka
    ESTUARINE COASTAL AND SHELF SCIENCE 78 (3) 541 - 550 0272-7714 2008/07 [Refereed][Not invited]
     
    To assess the potential of stable isotope ratios as an indicator of fish migration within estuaries, stable isotope ratios in important zooplankton species were analyzed in relation to estuarine salinity gradients. Gut contents from migratory juveniles of the eurybaline marine fish Lateolabrax japonicus were examined along the Chikugo River estuary of the Ariake Sea, which has the most developed estuarine turbidity maximum (ETM) in Japan. Early juveniles in March and April preyed primarily on two copepod species; Sinocalanus sinensis at lower salinities and Acartia omorii at higher salinities. Late juveniles (standard length > 40 mm) at lower salinities preyed exclusively on the mysid Acanthomysis longirostris until July and complementarily on the decapod Acetes japonicus in August. These prey species were collected along the estuary during the spring-summer seasons of 2003 and 2004, and their carbon and nitrogen stable isotope ratios (delta(13)C and delta(15)N) were evaluated. The delta(13)C values of prey species were distinct from each other and were primarily depleted within and in close proximity to the ETM (salinity < 10); S. sinensis (-26.6 parts per thousand) < Acanthomysis longirostris (-23.3 parts per thousand) < Acartia omorii (-21.1 parts per thousand) < Acetes japonicus (-18.5 parts per thousand). The overall gradient of delta(13)C with salinity occurred for all prey species and showed minor temporal fluctuations, while it was not directly influenced by the delta(13)C values in particulate organic matter along the estuary. In contrast to delta(13)C, the delta(15)N values of prey species did not exhibit any clear relationship with salinity. The present study demonstrated that delta(13)C has the potential for application as a tracer of fish migration into lower salinity areas including the ETM. (c) 2008 Elsevier Ltd. All rights reserved.
  • Akihide Kasai, Kousei Komatsu, Chiyuki Sassa, Yoshinobu Konishi
    FISHERIES SCIENCE 74 (1) 8 - 18 0919-9268 2008/02 [Refereed][Not invited]
     
    Recent surveys showed substantial aggregation of larvae of jack mackerel in the southern East China Sea, indicating intensive spawning grounds near Taiwan. A numerical model was applied to investigate transport and survival processes of eggs and larvae of jack mackerel from the spawning area to the nurseries. The results show that: (i) the distributions of larvae simulated by the model agreed well with those obtained by field survey; (ii) the stock of jack mackerel in the Sea of Japan is composed of both groups from north of Taiwan and from the western coast of Kyushu. It takes more than two months for the former to reach the Sea of Japan, while it is within 40 days for the latter; and (iii) large proportions of the eggs and larvae spawned off the north of Taiwan are transported rapidly to the Pacific side of Kyushu by the Kuroshio Current, and the rest slowly to the east or north-east along the continental slope in the East China Sea. In contrast to the larval flux, survivors are more abundant in the northern East China Sea than in the Pacific Ocean, indicating that survival in the northern East China Sea would determine the jack mackerel stock in Japan.
  • Ryo Sugimoto, Akihide Kasai, Toshihiro Miyajima, Kouichi Fujita
    JOURNAL OF OCEANOGRAPHY 64 (1) 39 - 48 0916-8370 2008/02 [Refereed][Not invited]
     
    Temporal changes in nitrogen isotopic composition (delta N-15) of the NO3- Pool in the water column below the pycnocline in Ise Bay, Japan were investigated to evaluate the effect of nitrification on the change in the delta N-15 in the water column. The delta N-15 of NO3- in the lower layers varied from -8.5 parts per thousand in May to +8.4 parts per thousand in July in response to the development of seasonal hypoxia and conversion from NH4+ to NO3-. The significantly N-15-depleted NO3- in May most likely arose from nitrification in the water column. The calculated apparent isotopic discrimination for water column nitrification (epsilon(nit) = delta N-15(substrate) - delta(15) N-product) was 24.5 parts per thousand, which lies within the range of previous laboratory-based estimates. Though prominent deficits of NO3- from hypoxic bottom waters due to denitrification were revealed in July, the isotopic discrimination of denitrification in the sediments was low (epsilon(denit) = similar to 1 parts per thousand). delta N-15(NO3) in the hypoxic lower layer mainly reflects the isotopic effect of water column nitrification, given that water column nitrification is not directly linked with sedimentary denitrification and the effect of sedimentary denitrification on the change in delta N-15(NO3) is relatively small.
  • Combined stable carbon isotope and C/N ratios as indicators of source and fate of organic matter in the Bangpakong River Estuary, Thailand.
    Thanomsak Boonphakdee, Akihide Kasai, Tateki Fujiwara, Pichan Sawangwong, Voravit Cheevaporn
    Environment Asia, 1, 28-36. 2008 [Refereed][Not invited]
  • Keita W. Suzuki, Akihide Kasai, Taro Ohta, Kouji Nakayama, Masaru Tanaka
    MARINE ECOLOGY PROGRESS SERIES 358 245 - 256 0171-8630 2008 [Refereed][Not invited]
     
    With conventional techniques it is difficult to evaluate the nursery value for migratory juveniles of Japanese temperate bass Lateolabrax japonicus within the Chikugo River estuary in Japan, especially in lower salinity areas where highly abundant prey organisms are distributed. In the present study stable carbon isotope ratios (delta C-13) were used as a migration tracer within the estuary. Based on preparatory information from diet-switch experiments and field observations of prey organisms, the ranges on which tissue VC values of juveniles should converge (convergence range) were determined in lower and higher salinity areas (LSA salinity < 10, HSA salinity > 10). For early juveniles, muscle delta C-13 values were analyzed and ages were determined by otolith increment counts. For more developed juveniles delta C-13 values were analyzed in muscle and liver, whose half-life values were 11.4 and 2.9 d, respectively. Temporal patterns of migration were estimated by comparing delta C-13 values in muscle and liver with the convergence ranges of both LSA and HSA. Early juveniles aggregated around the river mouth in March 2003 and the majority gradually ascended the river to LSA by April. Most of them stayed in LSA until August, while some began to expand their home ranges to HSA after July. In addition, it is suggested that the timing of ascent influenced the early growth of juveniles. Consequently, the potential importance of LSA was demonstrated during the first growth season of Japanese temperate bass in the estuary.
  • SUZUKI Keita W, SUGIMOTO Ryo, KASAI Akihide, SHOJI Jun, NAKAYAMA Kouji, TANAKA Masaru
    Bulletin of the Japanese Society of Fisheries Oceanography 水産海洋学会 71 (3) 190 - 198 0916-1562 2007/08 [Refereed][Not invited]
  • Kentaro Sakamoto, Ken Touhata, Michiaki Yamashita, Akihide Kasai, Haruhiko Toyohara
    FISHERIES SCIENCE 73 (3) 675 - 683 0919-9268 2007/06 [Refereed][Not invited]
     
    Cellulose digestion by Corbicula japonica was investigated according to the hypothesis that without any symbiotic aid, this organism can utilize cellulose as a carbon source. Enzymatic studies revealed the complete cellulase activity of this species, and molecular cloning resulted in the isolation of cDNA with an ORF encoding a 596-amino-acid protein that shares significant homology with abalone and termite cellulases with an amino acid identity of 52.2% and 50.5%, respectively. The isolated cellulase had a carbohydrate-binding module at the N-terminal region that was also reportedly present in abalone cellulase, and its mRNA were specifically expressed in the digestive gland. These findings strongly support the assumption that C. japonica has an endogenous cellulose, as well as abalones and termites. It is further believed that C. japonica plays an important roll in decomposing cellulose, and consequently contributes to the carbon-cycle in the aquatic environment, as termites do in terrestrial forests.
  • Akihide Kasai, Tatsuo Yamada, Hiroshi Takeda
    ESTUARINE COASTAL AND SHELF SCIENCE 71 (1-2) 210 - 217 0272-7714 2007/01 [Refereed][Not invited]
     
    Oxygen in the bottom water of the eastern basin of Hiuchi-nada. which is located in the central part of the Seto Inland Sea, Japan, is often depleted in summer. To clarify the formation mechanism of the hypoxic water mass, oxygen consumption rate experiments and detailed hydrographic observations were conducted. The experimental results showed that the oxygen consumption is unremarkable at the bottom in Hiuchinada, compared with other waters that show higher oxygen concentrations. From the hydrographic observations, the water is stratified and a cold dome, which corresponds to oxygen depleted water, is detected under the thermocline in the eastern basin of Hiuchi-nada. By contrast, outside of the dome, the water column is well mixed by strong tidal currents and the oxygen concentration is high. A prominent bottom front separates these two different water masses. There is a strong correlation between temperature and oxygen concentration under the thermocline (r(2) > 0.7). Residual currents from ADCP records show cyclonic circulation above the cold dome, while the water is nearly stationary inside the dome. Estimates of geostrophic currents from the density distribution are consistent with the observed flow pattern. These results indicate that the cold dome is isolated from the surrounding water Such that water exchange is insufficient, and thus the oxygen concentration reduces in Summer. Therefore, in Hiuchi-nada, the contribution of physical processes outweighs that of biochemical processes in the formation of the hypoxia. (c) 2006 Elsevier Ltd. All rights reserved.
  • KASAI Akihide, SUGIMOTO Ryo, AKAMINE Satomi
    海と空 海洋気象学会 82 (3) 53 - 60 0503-1567 2007 [Refereed][Not invited]
  • A Kasai, H Toyohara, A Nakata, T Miura, N Azuma
    FISHERIES SCIENCE 72 (1) 105 - 114 0919-9268 2006/02 [Refereed][Not invited]
     
    Carbon and nitrogen stable isotope ratios in tissue of the bivalve corbicula Corbicula japonica and particulate organic matter (POM) were measured in Lake Jusan, Lake Ogawara and Lake Shinji, which are the foremost fishing grounds for the corbicula in Japan, to determine their food sources. The bivalves in Lake Ogawara and Lake Shinji showed enriched isotope composition, while those in Lake Jusan were depleted. In addition, the difference in the isotope ratios between the sampling sites was remarkable in Lake Jusan. Chlorophyll concentrations were significantly higher in Lake Ogawara and Lake Shinji than those in the inflow rivers, although that in Lake Jusan was equivalent to that in the river. Residence time of river water was estimated at 1 day, 455 days and 88 days in Lake Jusan, Lake Ogawara and Lake Shinji, respectively. These values indicate that the bivalves in Lake Ogawara and Lake Shinji assimilate autochthonous phytoplankton, while those in Lake Jusan assimilate terrestrial matter in the upper reaches and marine phytoplankton in the lower reaches because of low production in the lake.
  • R Sugimoto, A Kasai, S Yamao, T Fujiwara, T Kimura
    ESTUARINE COASTAL AND SHELF SCIENCE 66 (1-2) 267 - 279 0272-7714 2006/01 [Refereed][Not invited]
     
    The composition and behavior of allochthonous particulate organic matter (POM) in the northern part of Ise Bay, Japan were investigated to elucidate the short-term variation in POM accompanying changes in river discharge. The behavior of POM was significantly regulated by hydrographic conditions, but behavior was different in the upper layer versus the middle and lower layers. The former showed simple dynamics controlled by the river plume, while the latter showed complex dynamics because of changes in river discharge and subsequent variation in estuarine circulation. During normal discharge, the contribution of riverine materials to POC in the surface water within the bay was negligible because most riverine organic matter is deposited before flowing into the bay. During high discharge, on the other hand, the contribution of riverine organic matter to total POM increased to 50% at similar to 10 km from the river mouth. Though riverine organic matter loads increased, the total amount of POC decreased around the river mouth due to flushing of phytoplankton. After river discharge, the contribution decreased rapidly. The behavior of POM in the middle and lower layers differed from that in the surface layer. At normal discharge, the influence of riverine organic matter was weak. During high discharge, high flooding temporarily weakened the bottom inflow, resulting in heavier riverine organic matter distributed from the river mouth to mid regions within the bay in the lower layer. The maximum contribution of riverine organic matter to total POM was estimated to be similar to 60% around 25 km from the river mouth. After high discharge, riverine POM in the lower layer was pushed to the bay head by enhanced estuarine circulation and was uplifted to the middle layer. The behavior of riverine POM dynamically changed in relation to fiver discharge, and exerted a significant influence on bottom water conditions in the bay. (c) 2005 Elsevier Ltd. All rights reserved.
  • KW Suzuki, A Kasai, K Nakayama, M Tanaka
    CANADIAN JOURNAL OF FISHERIES AND AQUATIC SCIENCES 62 (3) 671 - 678 0706-652X 2005/03 [Refereed][Not invited]
     
    As a first step for field applications of stable isotope techniques to investigate the migration of Japanese temperate bass (Lateolabrax japonicus) (Perciformes) juveniles, we conducted a diet switch experiment and fitted an exponential model to changes in stable carbon (delta(13)C) and nitrogen (delta(15)N) isotope ratios for muscle, fin, and liver. The trophic enrichment values were ranked liver < muscle < fin for delta(13)C (range -0.80e to +3.66e) and liver < fin < muscle for delta(15)N (+0.59e to +3.12e). The half-life values were similar for muscle and fin for both delta(13)C and delta(15)N (19.3-25.7 days), while those for liver were 5.3 days for delta(13)C and 14.4 days for delta(15)N. Both the delta(13)C and delta(15)N values of muscle reached the asymptotic value after a threefold body weight increase, reflecting the diet after the switch. These results suggest that fin is a useful substitute for muscle in field applications of stable isotope techniques and that liver, with a shorter half-life, has the potential to provide more recent information about migration.
  • A Kasai, A Nakata
    FISHERIES SCIENCE 71 (1) 151 - 158 0919-9268 2005/02 [Refereed][Not invited]
     
    Carbon and nitrogen isotopic ratios in tissue of the bivalve corbicula (Corbicula japonica) and particulate organic matter (POM) were measured along a salinity gradient in the Kushicla Estuary, Japan. The bivalve exhibited a gradual isotopic enrichment from the uppermost estuarine site (delta(13)C = -24.8parts per thousand and delta(15)N = 8.6parts per thousand) to the marine site (delta(13)C = -16.1parts per thousand and delta(15)N = 11.8parts per thousand). Using the concentration-weighted mixing model, the bivalves' food source is estimated from the isotope values for the bivalves and POM from terrestrial plants, marine phytoplankton and benthic microalgae. The results indicated that the contributions of benthic micro algae and phytoplankton were small, while terrestrial particulate matter is significantly important for the corbicula diet, although the contribution varies among sampling sites.
  • A Kasai, T Fujiwara, T Kimura, H Yamada
    JOURNAL OF OCEANOGRAPHY 60 (5) 817 - 824 0916-8370 2004/10 [Refereed][Not invited]
     
    To clarify the time change in water exchanges between Ise Bay and the adjacent ocean, repeated hydrographic observations were conducted along the longitudinal section in Ise Bay. The results show that the mixing condition at the bay mouth (Irago Strait) changed fortnightly in summer. During the spring tides, the strait water below the pycnocline was well-mixed and nearly homogeneous. By contrast, it was weakly stratified during the neap tide. There is a strong negative correlation between the tidal range and the density difference between the upper and lower layers at the strait. In summer, the intrusion depth of oceanic water into the bay and consequent hydrographic conditions inside the bay changed frequently according to the tidal strength. During the spring tides a prominent bottom front was created at the bay mouth, indicating that the strait water, which is a mixture of oceanic and bay waters, intruded through the middle layer. On the other hand, during the neaps, cold and saline oceanic water intruded through the bottom layer into the bay. The intrusion depth is significantly correlated with the tidal range. It is considered that the well-mixed strait water, which has a density equivalent to the middle layer inside the bay, is lighter than the bottom bay water and thus intrudes through the middle layer during the spring tides, while insufficient mixing makes the bottom water at the strait heavier than the bay water, leading to the bottom intrusion during the neap tides.
  • A Kasai, H Horie, W Sakamoto
    FISHERIES SCIENCE 70 (1) 11 - 20 0919-9268 2004/02 [Refereed][Not invited]
     
    Carbon and nitrogen isotopic ratios in the body of the bivalves Ruditapes philippinarum and Mactra veneriformis were measured to estimate the role of the bivalves in the ecosystem in an estuary. The isotopic signatures were compared with those obtained from particulate organic matter (POM) in the middle reach of the river, in the estuary, and off the estuary. Both the bivalves showed constant delta(13)C and delta(15)N values of approximately -17parts per thousand. and 10parts per thousand. that were significantly enriched compared with those for POM in the habitat (-25parts per thousand. and 4parts per thousand.). The relative contributions of terrestrial organic matter to the POM in the habitat and to the bivalve diet were estimated: the former was approximately 90% while the latter approximately 10%. This indicates that the bivalves select marine POM from the organic matter available in their habitat, and play a minor role in the direct removal of terrestrial particulate matter. Temporal changes in delta(13)C and delta(15)N for both bivalves were small, but a distinct decrease in delta(13)C was observed following a period of heavy rain. During rainfall the concentration of terrestrial material increased in the habitat, and the bivalves would then have to change their food sources temporarily.
  • 伊勢湾における河川流量の変動に伴う懸濁態有機物の変化
    杉本 亮, 笠井亮秀, 山尾理, 藤原建紀, 木村琢磨
    水産海洋研究 68 (3) 142 - 150 2004 [Refereed][Not invited]
  • 笠井 亮秀
    沿岸海洋研究 40 101 - 108 2003 [Refereed][Not invited]
  • Y Okazaki, H Nakata, S Kimura, A Kasai
    MARINE ECOLOGY PROGRESS SERIES 248 237 - 244 0171-8630 2003 [Refereed][Not invited]
     
    Focusing on an incidence of coastal water entrainment into the Kuroshio frontal region, we looked at the fate of anchovy larvae Engraulis japonicus originating from coastal spawning grounds and entrained into the frontal region with the coastal low salinity water. Drifters were released in the low salinity water of the Kuroshio frontal region, and observation and sampling were conducted during drifter tracking from 18 to 21 May 1997. Naupliar copepod abundance and copepod production were high in the low salinity water at an early phase of the tracking, but decreased with elapsed days. Anchovy larvae were most abundant on the coastal side of the Kuroshio, especially in the low salinity water. Their ages estimated from otoliths were consistent with those inferred from the advective transport speed from the coastal spawning ground. The estimated biological mortality rate of first-feeding larvae (less than 7 d old) in the low salinity water was 0.71 d(-1), which was high compared to rates previously reported for Engraulis spp. This high mortality could have been caused by poor nutritional conditions due to decreasing copepod production and abundance, suggesting that the offshore entrainment of fish larvae originating from coastal water could be unfavorable for their survival. The encounter with a frontal eddy would enhance food production and the subsequent survival of anchovy larvae in the frontal region; otherwise, they may perish due to low food availability.
  • Akihide Kasai, Shingo Kimura, Hideaki Nakata, Yuji Okazaki
    Journal of Marine Systems 37 (1-3) 185 - 198 0924-7963 2002/11/15 [Refereed][Not invited]
     
    The Pacific coastal areas of Japanese Island are major spawning grounds of various fishes. It is considered that large amount of eggs and larvae are dragged into the Kuroshio front so that the survival of fish larvae at the front is important for their recruitment. From this viewpoint, a low-salinity water mass, which was withdrawn from the coastal area to the Kuroshio front, was investigated by drifters, in addition to fine-scale hydrographic observations and water sampling in and around the Kuroshio frontal area off Enshu-nada. The drifters were transported to the east within the low-salinity water along the Kuroshio front in the first stage, and were thereafter entrained into an eddy, which was caused by the frontal meander. They moved closely to each other along the front, but diverged in the eddy. This movement of the drifters coincided with the deformation of low-salinity water mass the low-salinity water concentrated at the Kuroshio front surrounded by strong salinity gradients at first, while it spread out horizontally and became vague in the shallow surface layer in the frontal eddy. Comparing temperature sections across the front, the strong upwelling was detected in the eddy. Limiting factors for primary production and growth rates were calculated in six sections using the observed temperatures and concentrations of nutrients. In the frontal area of the Kuroshio, low concentration of nutrients limited the primary production shallower than 50 m. Due to the low productivity, concentration of chlorophyll a in the low-salinity water tended to decrease, although the initial concentration was high. Once the coastal water mass was entrained into the frontal eddy, on the contrary, the concentration recovered due to the enhanced primary production in the subsurface layer supported by the upwelling of nutrient-rich water. Fish larvae in the low-salinity water are assumed to use the new production in the eddy otherwise, they would starve. The entrainment process, which was probably caused by offshoreward movement of the Kuroshio, holds the key to successive survival and recruitment of fish larvae in the Kuroshio system. © 2002 Elsevier Science B.V. All rights reserved.
  • A Kasai, T Fujiwara, JH Simpson, S Kakehi
    CONTINENTAL SHELF RESEARCH 22 (11-13) 1579 - 1590 0278-4343 2002/07 [Refereed][Not invited]
     
    Recent surveys in Ise Bay, which is a major gulf-type region of freshwater influence in Japan, reveal that a cold dome is often observed in the stratified season. To elucidate the formation mechanism of the cold dome, detailed hydrographic and ADCP surveys were conducted in August 1995. The results show that a cold (T<20&DEG;C) water mass existed under the thermocline in the western basin of the bay. By contrast, in the middle layer of the eastern basin, there was mixed water, which exhibited characteristics equivalent to the water in the Irago Strait. A prominent bottom front separated these two different water masses. The ADCP results show a strong inflow in the form of a geostrophic current flowing above the bottom front, while the flow speed was weak in the cold water mass. The inflow area corresponded with the mixed water area, suggesting that the strait water would intrude into the bay along the eastern coast. In the western half of the basin, on the other hand, relict spring water is excluded from the exchange circulation and was trapped beneath the thermocline, where it formed the cold dome. The formation of the cold dome by this process is investigated using a three-dimensional model with two different density structures; a stratified and mixed region. The model results strongly support the formation mechanism of the cold dome, as the observed density and flow fields are successfully demonstrated. The key point to control the mechanism is the coexistence of the stratified and the mixed region. (C) 2002 Elsevier Science Ltd. All rights reserved.
  • T Fujiwara, T Takahashi, A Kasai, Y Sugiyama, M Kuno
    ESTUARINE COASTAL AND SHELF SCIENCE 54 (1) 19 - 31 0272-7714 2002/01 [Refereed][Not invited]
     
    Seasonally occurring hypoxia in Ise Bay, Japan was studied by comparing flow structures and ages of water parcels. Age is defined as the elapsed time after isolation of the water parcel from the oxygen source. In this bay, bay water is strongly stratified and advective transport by the estuarine gravitational circulation dominates from April to October. In contrast, the strong tidal current keeps the water column well mixed and oxygen-rich from top to bottom in the bay-mouth strait, which connects the bay with the Pacific Ocean. The estuarine circulation in Ise Bay is influenced by the effect of the Earth's rotation; the well-mixed water intrudes into the eastern half of the bay under the pycnocline with the land on its right (looking down current). Surrounded by this strait water, relatively cooler water (cold pool) remains on the bottom in the western half of the bay, isolated from the seasonal heating. Comparing the temperature of water under the pycnocline in the bay with the temperature of the strait water, we can estimate an age (tau) of water parcels. This age coincides with the mean residence time, which has traditionally been used. This method gives an age to the water parcel at a point under the pycnocline in the bay. Oxygen concentration under the pycnocline indicates a high correlation coefficient (R-2 > 0.8) with age. The decrease of oxygen concentration during the period tau gives the oxygen consumption rate (OCR). The OCRs under the pycnocline were calculated from May to August. The OCR is approximately homogeneous independent of location in the bay. Moreover, monthly values of OCRs are also approximately constant from May to August, despite the mean temperature increase from 14.4 to 20.4 degreesC during this period. Known physical processes explain 80% of the spatial and temporal variation in oxygen concentration. In contrast, biochemical processes provide homogeneous OCR and play only a minor role in the variation in oxygen concentration. (C) 2002 Elsevier Science Ltd.
  • 笠井亮秀, 藤原建紀, 多田光男
    海岸工学論文集 Japan Society of Civil Engineers 48 (1) 436 - 440 0916-7897 2001/10/20 [Refereed][Not invited]
  • KASAI Akihide, TADA Mitsuo, FUJIWARA Tateki
    海と空 海洋気象学会 77 (2) 99 - 106 0503-1567 2001/09/07 [Refereed][Not invited]
  • 笠井亮秀, 川西里佳, 藤原建紀
    水産海洋研究 64 (4) 235 - 243 2000/11/30 [Refereed][Not invited]
  • A Kasai, W Sakamoto, Y Mitsunaga, S Yamamoto
    FISHERIES OCEANOGRAPHY 9 (3) 259 - 270 1054-6006 2000/09 [Refereed][Not invited]
     
    The long-term behaviour of immature yellowtails, Seriola quinqueradiata, was studied using electronic data-recording tags in Sagami Bay, Japan, during the autumn and early winter. Temperature or depth data were continuously recorded for 5-69 days on six yellowtails. The temperature recorded from the 0-year-old yellowtails showed only small variations (< 0.5 degrees C day(-1)) around the SST on the coast, indicating the 0-years stayed in the immediate coastal area with little horizontal movement. The 1-year-old yellowtail showed larger temperature variations that reached 3 degrees C day(-1), which implies distinctly larger horizontal movements than the 0-year-olds. Depth records showed the 0-years stayed around 10 m while the 1-year yellowtail swam in deeper water (mainly 10-30 m) with large variations. The latter often dived to 40 m in the daytime, but shallower than the depth of the thermocline. Both temperature and depth records showed apparent diurnal patterns. Comparing the fish data with environmental conditions, it is suggested that 1-year yellowtails stay close to the coast during the night, move at dawn to feed in the daytime and return at dusk via a frontal zone. In addition, wind stress could change yellowtails' behaviour.
  • A Kasai, AE Hill, T Fujiwara, JH Simpson
    JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 105 (C7) 16961 - 16969 0148-0227 2000/07 [Refereed][Not invited]
     
    Recent surveys in various regions of freshwater influence have shown considerably different now patterns in each region. An analytical model including viscous effects and the Earth's rotation is proposed to examine the along-channel flow pattern and to explain the differences. Model results show that the flow pattern is strongly dependent on the Ekman number E. With a large Ekman number (E > 1) the system is governed by gravitational circulation, and thus horizontal density gradients in along-channel direction are important. The whole water column is in the Ekman layer and consequent jet inflow penetrates the surface over a deep depression if the bottom topography varies in a cross-channel direction. With an intermediate Ekman number (E similar to 0.1) this jet inflow concentrates in the lower layer in which the viscosity still plays an important role. The flow in the upper layer is, on the other hand, determined by the geostrophic balance. The contribution by the geostrophic flow becomes larger so that the cross-channel density gradients are important when the Ekman number is small (E < 0.01). Since the Ekman layer is clung to the bottom, the jet inflow exists only in the thin bottom layer. The hydrographic and acoustic Doppler current profiler surveys were conducted in Ise Bay, Japan. Both the density structure and the flow pattern were different from those observed in many drowned river valleys, a strong jet inflow existed in the lower layer over the depression while the flow in the upper layer suggested anticyclonic circulation. The estimated Ekman number is 0.07 bn the bay and thus the observed pattern is consistent with the model result when E = 0.1.
  • H Nakata, S Kimura, Y Okazaki, A Kasai
    ICES JOURNAL OF MARINE SCIENCE 57 (1) 143 - 151 1054-3139 2000/02 [Refereed][Not invited]
     
    This paper discusses the implications of the meso-scale eddies, which are caused by frontal disturbances of the Kuroshio Current, for larval transport, distribution and food availability for Japanese anchovy, Engraulis japonicus (Houttuyn). It is a ubiquitous feature of the Kuroshio Front that wave-like meanders, with wavelengths of 100-400 km, generate cyclonic frontal eddies off the Pacific coast of the island of Japan. These eddies are likely to affect larval transport and the survival of the coastal spawning fish such as anchovy in the Kuroshio region by possibly moving coastal water offshore to the frontal region. With this in mind, a frontal eddy was tracked from 18-23 May 1994 in the Enshu-nada Sea, where one of large spawning grounds of anchovy was found. Intensive transect surveys across the eddy were made to collect anchovy eggs and larvae simultaneously with prey organisms e.g. naupliar and copepodite copepods. These surveys showed that anchovy eggs and larvae hatched in the coastal water of the Enshu-nada Sea were entrained into the frontal eddy and transported along the Kuroshio front, possibly recruiting to coastal nurseries in the Enshu-nada Sea. In addition, the upwelling of nutrient-rich water in the vicinity of this cyclonic eddy enhanced primary production and subsequent copepod production, providing potentially favourable conditions for the feeding and growth of the anchovy larvae entrained in the eddy. (C) 2000 International Council for the Exploration of the Sea.
  • A Kasai, TP Rippeth, JH Simpson
    CONTINENTAL SHELF RESEARCH 19 (14) 1833 - 1848 0278-4343 1999/11 [Refereed][Not invited]
     
    A well-defined front in temperature and salinity separates the stratified Clyde Sea water from the vertically well mixed water of the North Channel. The detailed structure of the front was observed in autumn 1990 by a combination of, repeated crossings of the front using a shipborne ADCP and a towed undulating CTD system, and the deployment of a fixed mooring system with temperature, salinity and velocity sensors for a period of 12 days. The results show that the front was situated on the Great Plateau near a contour of log(10)(H/U-2(3)) = 2.7 similar to 3.7 where H is the water depth and U-2 the amplitude of M-2 tidal velocity. The temperature structure in the Clyde Sea was inverted and the Clyde Sea surface temperature was lower than that of the vertically well mixed water in the North Channel. Since the salinity gradient was stronger than the temperature gradient with fresher water on the surface, the density structure was predominantly controlled by salinity. There were indications of warm and saline bottom water upwelling on the mixed side of the front during spring tides. This upwelling disappeared and the salinity and temperature structure at the front was more diffuse during the neap tide period. A jet-like along-front residual current was observed flowing to the northwest in the surface layer with a counter flow to the southeast in the bottom layer. The vertical difference in velocity was about 9 cm s(-1) and was approximately consistent with the shear determined from the thermal wind relation. Both cross- and along-front components of the current observed at the mooring station varied in response to the advection of the front, although both components had large variations with periods of less than one day and several days. The front was advected past the mooring system by a mean flow from the North Channel to the inner basin, while oscillating 3-5 km back and forth with the tidal currents. From the velocity at a current meter mooring and CTD data, the front was estimated to have moved up to 20 km during the observational period and the cross frontal velocity was inferred to be 3-4 cm s(-1). (C) 1999 Elsevier Science Ltd. All rights reserved.
  • 藤原建紀, 山尾理, 高橋鉄哉, 笠井亮秀, 杉山陽一, 原田一利
    海岸工学論文集 46 (2) 1211 - 1215 1999/10/20 [Refereed][Not invited]
  • Y Mitsunaga, W Sakamoto, N Arai, A Kasai
    NIPPON SUISAN GAKKAISHI 65 (1) 48 - 54 0021-5392 1999/01 [Refereed][Not invited]
     
    Two experiments were executed to investigate the correlation among water temperature, metabolic rate and swimming behavior of red sea bream Pagrus major. In the former experiment, the relationship between oxygen consumption and water temperature was measured in laboratory respirometry trials. The result shelved water temperature (T, degrees C) has the following correlation with oxygen consumption (OC, mg min.(-1) kg(-1)); OC=1.47+0.01x1.22(T), R=0.92. In the latter experiment, a wild adult fish was tracked in the open sea using an ultrasonic transmitter to record the horizontal migration paths, vertical swimming trajectory and ambient water temperature. The fish rested on the bottom during the day. While at night, it swam up and down within the depth range 30 to 80 m. The ambient water temperature ranged from 18.5 to 22.9 degrees C. In the period of resting, the red sea bream was estimated to consume oxygen ranging from 1.91 to 2.55 mg min.(-1) kg(-1), in the open ocean. During the experimental period of 28 days, the fish remained within a shoal and moved only small horizontal distances. Fluctuation of ambient water temperature seemed to have little effect on the swimming behavior of red sea bream.
  • Akihide Kasai, Wataru Sakamoto, Yasushi Mitsunaga, Shotaro Yamamoto
    Nippon Suisan Gakkaishi (Japanese Edition) 64 (2) 197 - 203 0021-5392 1998 [Refereed][Not invited]
     
    An acoustic transmitter and two micro data recording tags were used to observe the behavior of yellowtails Seriola quinqueradiata, in Sagami Bay, Japan from 24 October through 19 November. Depth data were continuously recorded for 23 days and temperature data for 27 days with a 20-minute interval. The yellowtails showed an apparent diurnal vertical migration pattern in their movements they crossed the thermocline actively during the daylight hours, but calmed down and remained in the shallow layer above the thermocline at night. Their movements were changed by environmental temperature variation: 1) After the ambient water temperature rapidly decreased, a change was seen in the average depth and pattern in the vertical movement of the yellowtail. 2) They could move vertically to avoid the warm water from the Kuroshio because no ambient temperature rise and no shallower position were observed when the warm water intruded into the bay from the Kuroshio.
  • 藤原建紀, 宇野奈津子, 多田光男, 中辻啓二, 笠井亮秀, 坂本亘
    Doboku Gakkai Ronbunshuu B Japan Society of Civil Engineers 44 (2) 1061 - 1065 0916-7897 1997/11 [Refereed][Not invited]
  • FUJIWARA Tateki, UNO Natsuko, TADA Mitsuo, NAKATSUJI Keiji, KASAI Akihide, SAKAMOTO Wataru
    海と空 海洋気象学会 73 (2) 63 - 72 0503-1567 1997/09 [Not refereed][Not invited]
  • A Kasai, T Sugimoto, H Nakata
    FISHERIES SCIENCE 63 (3) 372 - 377 0919-9268 1997/06 [Refereed][Not invited]
     
    We have numerically modeled the transport and survival processes of Japanese sardine eggs and larvae Sardinops melanostictus in the Kuroshio-Oyashio region to investigate the dependence of yearly recruitment of the sardine on the mortality rate during the early life stages. The model covers from 130 degrees E to 160 degrees E and simulates the Kuroshio Current and wind-induced current resulting from the winter monsoon in a simple way. As a biological process, natural mortality of the eggs and larvae is parameterized by area and year, considering the oceanographic condition such as the extent of southward intrusion of the Oyashio. The year-to-year variations in the amount of survivors simulated by the model are compared to that of one-year sardine stock based on the field data. The variation in the abundance of one-year old sardine is well correlated to that of the surviving juveniles off the east but not the south of Japan, both of which are calculated by the model. This indicates that the survival condition after the postlarval period off the east coast of Japan, which is strongly affected by the Oyashio, could play an important role in determining the year class strength. A strong year class can be formed by the numerous juveniles transported to the east and/or by the good survival condition in the eastern offshore region of Japan.
  • S Kimura, A Kasai, H Nakata, T Sugimoto, JH Simpson, JVS Cheok
    ICES JOURNAL OF MARINE SCIENCE 54 (2) 179 - 192 1054-3139 1997/04 [Refereed][Not invited]
     
    Temporal and spatial changes in nutrient and chlorophyll distributions caused by frontal disturbances of the Kuroshio, a western boundary current in the Pacific Ocean, are presented. The regions of high nitrate and phosphate concentrations are associated with an eddy of positive vorticity which separates from the Kuroshio front within a few days of generation. The nutrients supplied to the euphotic layer by upwelling and mixing in the cyclonic eddy accelerate primary production in the frontal region. The specific growth rate calculated from temporal changes in chlorophyll and nitrate concentrations, of 0.8 d(-1) is considerably larger in the offshore region. According to a numerical simulation made using a turbulent closure model a chlorophyll maximum occurs during the fifth day after the generation of the eddy and the growth rate in the euphotic layer is in good agreement with that estimated from observations. After the peak production the growth becomes nutrient limited. Since the frontal disturbances occur in association with short-term fluctuations in the Kuroshio frontal meander, which has a period of a few weeks, the biological production enhancement by this kind of eddy is expected to occur with similar frequency, It is estimated that the total annual nitrogen input to the region via the eddies could result in a carbon production rate of 40 gC m(-2) y(-1). (C) 1997 International Council for the Exploration of the Sea.
  • A Kasai, N Koizumi, T Sugimoto
    SURVIVAL STRATEGIES IN EARLY LIFE STAGES OF MARINE RESOURCES 219 - 226 1996 [Refereed][Not invited]
  • Kasai A, Kishi M J, Sugimoto T
    Canadian Journal of Fisheries and Aquatic Sciences 121 547 - 552 1995 [Refereed][Not invited]
  • S KIMURA, A KASAI, T SUGIMOTO
    FISHERIES SCIENCE 60 (6) 635 - 641 0919-9268 1994/12 [Refereed][Not invited]
     
    In the Kumano-nada and Enshu-nada Seas, warm water masses from the Kuroshio intrude into the coastal area depending on the paths type of the Kuroshio. Associated with the intrusions which occur with a period of 50 days from the Izu Peninsula when the Kuroshio takes the B-type path, yellowtail adults called buri migrate to the coastal area. However, the long time-lag between the intrusion and buri catch causes a negative relationship between the temperature and catch. The results suggest that the buri school migrates westward after the water mass has diffused. Since there is a positive relationship between temperature and catch associated with very rapid intrusions when the Kuroshio takes the C-type path, it is necessary to distinguish oceanographic phenomena in order to understand the fish behavior in response to offshore oceanic changes. In addition, the seasonal horizontal temperature gradient should be considered when estimating the optimum temperature range for fish because the relative temperature change greatly affects fish migration rather than the optimum temperature.
  • Akihide Kasai, Shingo Kimura, Takashige Sugimoto
    Journal of Oceanography 49 (6) 607 - 624 0916-8370 1993/11 [Refereed][Not invited]
     
    Sea surface temperature (SST) has been measured in the south of Japan using a thermometer set up in the ferry boat to investigate the characteristics of the warm water intrudes into the coastal areas from the Kuroshio. Time series analysis was applied to the SST data with satellite images and hydrographic observation data from April 1987 to September 1989. The results indicate that the warm Kuroshio water intruded into the coastal areas on the Enshu-nada and the Kumano-nada Seas intermittently with periods of about 50 and 20 days associated with the fluctuation of the Kuroshio path and the Kuroshio frontal disturbance respectively. The intrusion with a 50-day period was dominant when the Kuroshio took a stationary small meander path (B- and C-types). The warm water spread to the west at 20 cm s-1, and was estimated to have a depth of 150 m at least and supply enough heat to make up the loss due to the evaporation in the coastal area. During the straight path of the Kuroshio, it was detected that the warm water intruded into coastal areas only with a 20-day period. The warm water that intrudes with a period of 20 days spreads to the west at 25 cm s-1 in a small scale. © 1993 Journal of the Oceanographic Society of Japan.
  • 笠井 亮秀, 岸道郎, 杉本隆成
    水産海洋研究 水産海洋学会 56 (2) 99 - 105 0916-1562 1992/04 [Refereed][Not invited]
  • AKIHIDE KASAI, MICHIO J. KISHI, TAKASHIGE SUGIMOTO
    Fisheries Oceanography 1 (1) 1 - 10 1365-2419 1992 [Refereed][Not invited]
     
    We have numerically modeled the advection and diffusion of sardine eggs and larvae to investigate the larval transport processes of Japanese sardine from the spawning grounds by the Kuroshio. The results indicated that the offshore drift current induced by the winter monsoon and the location of the spawning ground have significant effects on the survival of the Japanese sardine. The contribution of the drift current, the distance of the spawning ground from the Kuroshio axis, and the eddy diffusivity to the larval retention in the coastal area is approximately expressed by the following equation: where R is the retention rate in the coastal area, a the variance of initial distribution of eggs, T the time after the eggs were spawned, – V0 the velocity of the wind‐induced offshore current, y0 the distance of the center of the spawning area from the Kuroshio axis, and K the coefficient of horizontal eddy diffusivity. The year‐to‐year variation in larval survival rates stimulated by the two‐dimensional model are consistent with those estimated previously by using field data of egg and larval abundance during 1978–1988. Copyright © 1992, Wiley Blackwell. All rights reserved

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  • 土橋稜, 上野洋路, 加藤陸, 閻乃筝, 向井徹, 安間洋樹, 野村大樹, 伊藤幸彦, 笠井亮秀  日本水産学会大会講演要旨集(CD-ROM)  2021-  2021
  • 川上達也, 山崎彩, 上野洋路, 兵藤晋, 笠井亮秀  水産海洋学会研究発表大会講演要旨集  2021-  2021
  • 笠井亮秀, 山崎彩, 安孝珍, 山中裕樹, 亀山哲, 益田玲爾, 東信行, 木村伸吾, 木村伸吾, 唐木達郎, 黒川優子, 山下洋  日本水産学会大会講演要旨集(CD-ROM)  2021-  2021
  • 小林志保, 久米学, AHN Hyojin, 邉見由美, LAVERGNE Edouard, 寺島佑樹, YE Feng, YE Feng, 亀山哲, 甲斐嘉晃, 山下洋, 笠井亮秀  日本水産学会大会講演要旨集  2020-  2020
  • 大庭ゆりか, 伊勢武史, 笠井亮秀, 亀山哲, AHN Hyojin, 久米学, 寺島佑樹, YE Feng, 山下洋  日本生態学会大会講演要旨(Web)  67th-  2020
  • 唐木達郎, 坂本圭, 木村伸吾, 木村伸吾, 笠井亮秀  日本海洋学会大会講演要旨集  2020-  2020
  • 山崎彩, 山中裕樹, 伊藤元裕, 木村伸吾, 笠井亮秀  個体群生態学会大会プログラム・講演要旨集(Web)  36th-  2020
  • Hiroaki Murakami, Seokjin Yoon, Akihide Kasai, Toshifumi Minamoto, Satoshi Yamamoto, Masayuki K. Sakata, Tomoya Horiuchi, Hideki Sawada, Michio Kondoh, Yoh Yamashita, Reiji Masuda  FISHERIES SCIENCE  85-  (6)  1109  -1109  2019/11  
    In the original publication the text in right column of page 330, the sequences of primers were incorrectly published as.
  • 笠井 亮秀, 高田 真悟, 山崎 彩, 定行 洋亮, 木村 伸吾, 安 孝珍, 寺島 佑樹, 久米 学, 益田 玲爾, 山下 洋, 山中 裕樹, 今藤 夏子, 亀山 哲, 東 信行  平成31年度日本水産学会春季大会  2019-  p.38  2019/03/29  [Not refereed][Not invited]
  • Alisa Kutzer, 小巻 拓平, 野田 琢嗣, 和田 敏裕, 久米 学, 寺島 佑樹, 堀 友彌, 高木 淳一, 三田村 啓理, 笠井 亮秀, 荒井 修亮, 山下 洋  平成31年度日本水産学会春季大会  2019-  p.38  2019/03/29  [Not refereed][Not invited]
  • 久米学, AHN Hyojin, 寺島佑樹, LAVERGNE Edouard, YE Feng, 亀山哲, 邉見由美, 甲斐嘉晃, 伊勢武史, 笠井亮秀, 山下洋  日本魚類学会年会講演要旨  52nd-  2019
  • 笠井亮秀, 安孝珍, 久米学, 寺島佑樹, FENG Ye, 亀山哲, 宮正樹, 山下洋  水産海洋学会研究発表大会講演要旨集  2019-  2019
  • 定行洋亮, 笠井亮秀, 山下洋, 東信行, 山中裕樹, 亀山哲, 久米学, 和田敏裕, 木村伸吾  水産海洋学会研究発表大会講演要旨集  2019-  2019
  • 笠井 亮秀, 高田 真悟, 山崎 彩, 定行 洋亮, 木村 伸吾, 安 孝珍, 寺島 佑樹, 久米 学, 益田 玲爾, 山下 洋, 山中 裕樹, 今藤 夏子, 亀山 哲, 東 信行  2018年度水産海洋学会研究発表大会  2018-  p.83  2018/11/17  [Not refereed][Not invited]
  • 舞鶴湾におけるマアジとカタクチイワシの環境DNAの水平・鉛直分布 口頭
    村上 弘章, 山本 哲史, 源 利文, 南 憲吏, 宮下 和士, 深谷 肇一, 尹 錫鎭, 笠井 亮秀, 澤田 英樹, 鈴木 啓太, 益田 玲爾, 山下 洋, 近藤 倫生  平成30年度日本水産学会春季大会  p.28  2018/03/27  [Not refereed][Not invited]
  • 定行 洋亮, 山中 裕樹, 久米 学, 山下 洋, 山崎 彩, 笠井 亮秀  平成30年度日本水産学会春季大会  2018-  p.38  2018/03/27  [Not refereed][Not invited]
  • 安佛かおり, 宮原一隆, 山本圭吾, 秋山諭, 笠井亮秀  日本生態学会大会講演要旨(Web)  65th-  2018
  • 流動モデルを用いた環境DNA濃度分布の再現
    笠井亮秀, 尹錫鎭  海洋と生物  234-  23  -27  2018  [Not refereed][Not invited]
  • 仙台湾におけるスズキの卓越年級群の形成要因 口頭
    外舘 香奈, 冨士 泰期, 高林 長将, 曽我部 共生, 鈴木 勇人, 栗田 豊, 山下 洋, 笠井 亮秀  2017年度水産海洋学会研究発表大会  p.92  2017/11/19  [Not refereed][Not invited]
  • 異なるハビタットにおけるスズキ稚魚の生息密度と環境DNAの関係
    村上 弘章, 曽我部 共生, 鈴木 勇人, 源 利文, 笠井 亮秀, 鈴木 啓太, 山下 洋, 益田 玲爾  2017年日本水産学会春季大会  p.33  2017/03/28  [Not refereed][Not invited]
  • 流域圏における農林水産業と地域振興-世界農業遺産国東半島・宇佐地域の森川里海-
    田村 勇司, 杉本 亮, 笠井 亮秀, 横山 寿, 山下 洋  2017年日本水産学会春季大会  p.255  2017/03/26  [Not refereed][Not invited]
  • WATANABE KENTA, FUKUSHIMA KEITARO, KASAI AKIHIDE, YOSHIOKA TAKAHITO, YAMASHITA YOH  NIPPON SUISAN GAKKAISHI  83-  (6)  1014  -1014  2017  [Not refereed][Not invited]
  • Numerical simulation of the transport of temperate seabass eggs and larvae in a region of freshwater influence 口頭
    Yoon, Seokj, Suzuki, Keita, W, Yamashita, Yoh, Kasai, Akihide  KOFFST International Conference 2017  2017  [Not refereed][Not invited]
  • Comparison of aquatic biological production systems between two rivers in Oita Prefecture, Japan ポスター
    Kanzaki, Toko, Kume,Manabu, Hashiguchi, Shunya, Harada, Mami, Mochioka, Noritaka, Kasai, Akihide, Tamura, Yuji, Yokoyama, Hisashi, Arai, Nobuyuki, Yamashita, Yoh  日本水産学会国際シンポジウム  SP05  -7  2017  [Not refereed][Not invited]
  • A Lagrangian modeling approach for the transport of temperate seabass eggs and larvae in a region of freshwater influence 口頭
    Yoon, Seokj, Suzuki, Keita, W, Yamashita, Yoh, Kasai, Akihide  日本水産学会国際シンポジウム  SO04  -23  2017  [Not refereed][Not invited]
  • 大分県国東半島における森里海連環‐陸起源懸濁物質の海域への流出
    橋口 峻也, 神崎 東子, 田村 勇司, 荒川 久幸, 山下 洋, 荒井 修亮, 笠井 亮秀  平成28年度日本水産学会近畿支部例会  p.24  2016/12/18  [Not refereed][Not invited]
  • 大分県国東半島における森里海連環‐ニホンウナギを指標として‐
    神崎 東子, 橋口 峻也, 原田 真美, 鶴川 亮太, 望岡 典隆, 田村 勇司, 山下 洋, 荒井 修亮, 笠井 亮秀  平成28年度日本水産学会近畿支部例会  p.25  2016/12/18  [Not refereed][Not invited]
  • ウナギの石倉漁と資源保護に関する研究
    原田 真実, 神崎 東子, 橋口 峻也, 望岡 典隆, 鶴川 亮太, 清水 夏樹, 横山 寿, 田村 勇司, 笠井 亮秀, 山下 洋  平成28年度日本水産学会近畿支部例会  p.26  2016/12/18  [Not refereed][Not invited]
  • 夏季の国東半島における河川水中の溶存無機態窒素・リンの動態の俯瞰的評価
    理塀隆人, 杉本亮, 田村勇司, 笠井亮秀, 山下 洋  平成28年度日本水産学会中部支部会  p.  2016/12/03  [Not refereed][Not invited]
  • Commons management of estuarine ecosystem services: the case study for Japanese eels (Anguilla japonica)
    Harada,M, Onoue,M, Kanzaki,T, Hashiguchi,S, Tsurukawa,R, Mochioka,N, Tamura,Y, Shimizu,N, Kasai,A, Yamashita,Y  ECSA(Estuarine Coastal Shelf Association)  GS3C O3-39  2016/09  [Refereed][Not invited]
  • Connectivity of forests, rivers and seas −Relationship between land-use and aquatic biological production
    Kanzaki,T, Sogabe,T, Hashiguchi,S, Harada,M, Tsurukawa,R, Mochioka,N, Kasai,A, Tamura,Y, Yokoyama,H, Arai,N, Yamashita,Y  ECSA(Estuarine Coastal Shelf Association)  GS3C O3-39  2016/09  [Refereed][Not invited]
  • Connectivity of forests, rivers, and seas- Relation between land-use and water quality
    Hashiguchi,S, Kanzaki,T, Kasai,A, Tamura,Y, Sugimoto,R, Rihei,T, Arai,N, Yamashita,Y  ECSA(Estuarine Coastal Shelf Association)  GS3C O3-39  2016/09  [Refereed][Not invited]
  • 夏季の大分県国東半島における河川水中の溶存無機態窒素・リンの動態
    理塀 隆人, 杉本 亮, 田村 勇司, 笠井 亮秀, 山下 洋  2016年度地球惑星連合大会  A-CG23-03  2016/05/24  [Not refereed][Not invited]
  • 笠井 亮秀  水産海洋研究 = Bulletin of the Japanese Society of Fisheries Oceanography  80-  (2)  146  -152  2016/05
  • スズキ稚魚の成長に伴う成育場利用の変化
    笠井 亮秀, 曽我部 共生, 鈴木 勇人, 鈴木 啓太, 山下 洋  平成28年度日本水産学会春季大会  p.40  2016/03/27  [Not refereed][Not invited]
  • 村上弘章, 尹錫鎭, 笠井亮秀, 源利文, 山本哲史, 坂田雅之, 堀内智矢, 澤田英樹, 益田玲爾  日本水産学会大会講演要旨集  2016-  35  2016/03/26  [Not refereed][Not invited]
  • 丹後海におけるスズキ仔稚魚の成育場の利用特性 ポスター
    曽我部 共生, 鈴木 勇人, 笠井 亮秀, 鈴木 啓太, 山下 洋  日本生態学会第63回仙台大会  2016/03  [Not refereed][Not invited]
  • 竹茂愛吾, 伊藤幸彦, 笠井亮秀, YIN Shengle, YIN Shengle, 木村伸吾, 木村伸吾  月刊海洋  48-  (7)  2016
  • 丹後海舞鶴湾におけるスズキ稚魚の成育場の利用特性
    曽我部 共生, 笠井 亮秀, 鈴木 啓太, 山下 洋, 荒井 修亮, 鈴木 勇人  2015年度日本水産学会近畿支部後期例会  p.13  2015/12/13  [Not refereed][Not invited]
  • 国東半島における陸起源物質負荷量の降雨に伴う短期変動
    橋口 峻也, 笠井 亮秀, 田村 勇司, 山下 洋, 荒井 修亮  2015年度日本水産学会近畿支部後期例会  p.21  2015/12/13  [Not refereed][Not invited]
  • 丹後海におけるスズキの初期生活史
    笠井亮秀, 冨士泰期, 曽我部共生, 政友明秀, 鈴木啓太, 山下洋  東京大学大気海洋研究所共同利用集会「海洋における生物生産機構の多様性と連関−黒潮生態系から沿岸複合生態系まで−」  2015/12/02  [Not refereed][Not invited]
  • 沿岸域の循環と食物網動態：複合生態系モデリング
    伊藤 幸彦, 竹茂 愛吾, 笠井 亮秀, 尹 盛楽, 木村 伸吾  東京大学大気海洋研究所共同利用集会「海洋における生物生産機構の多様性と連関−黒潮生態系から沿岸複合生態系まで−」  2015/12/02  [Not refereed][Not invited]
  • 複合生態研究における丹後海の流動環境
    木村 伸吾, 笠井 亮秀, 伊藤 幸彦, 銭本 慧, 竹茂 愛吾, 三宅 陽一, 鈴木 啓太, 山下 洋, 渡邊 良朗  東京大学大気海洋研究所共同利用集会「海洋における生物生産機構の多様性と連関−黒潮生態系から沿岸複合生態系まで−」  2015/12/01  [Not refereed][Not invited]
  • マナマコ浮遊幼生の湾内滞留機構について
    澤田 英樹, 山? 哲也, 上野 正博, 山下 洋, 笠井 亮秀  2015年度日本ベントス学会・日本プランクトン学会合同大会  2015/09/04  [Not refereed][Not invited]
  • 山下洋, 笠井亮秀, 冨士泰期, 秋山諭, 渡辺謙太, 上野正博, 鈴木啓太  平成32年度日本水産学会春季大会講演要旨集  2015-  p.63  2015/03  [Not refereed][Not invited]
  • 沿岸複合生態系の構造と資源生物生産機能-３．丹後海における基礎生産構造、口頭
    笠井亮秀, 安佛かおり, 尹錫鎭, 鈴木啓太, 山下洋, 渡辺謙太, 舟橋達宏  平成31年度日本水産学会春季大会講演要旨集  p.63  2015/03  [Not refereed][Not invited]
  • 木村伸吾, 笠井亮秀, 伊藤幸彦, 銭本慧, 竹茂愛吾, 三宅陽一, 鈴木啓太, 山下洋, 渡邊良朗  平成30年度日本水産学会春季大会講演要旨集  2015-  p.63  2015/03  [Not refereed][Not invited]
  • 安佛かおり, 笠井亮秀, 一見和彦, 山口一岩, 大美博昭, 秋山諭, 宮原一隆, 山本昌幸  日本生態学会大会講演要旨(Web)  62nd-  2015
  • 安佛かおり, 一見和彦, 山口一岩, 大美博昭, 秋山諭, 宮原一隆, 山本昌幸, 笠井亮秀  日本地球惑星科学連合大会予稿集(Web)  2015-  2015
  • 竹茂愛吾, 伊藤幸彦, 笠井亮秀, 尹盛楽, 木村伸吾  水産海洋学会研究発表大会講演要旨集  2015-  2015
  • Artificial upwelling maintains favorable summer environment for farmed oysters
    Mizuta DD, Kasai A, Yamaguchi H, Nakata H  Global aquaculture advocate  7-  16  -18  2015  [Not refereed][Not invited]
  • 生息環境ごとのスズキ仔稚魚の成長の差異とその要因、口頭
    曽我部共生, 高林長将, 冨士泰期, 鈴木啓太, 笠井亮秀, 山下洋  2014年度水産学会近畿支部例会講演要旨集  p.8  2014/11/22  [Not refereed][Not invited]
  • スズキ稚魚食性の海域間比較、口頭
    高林長将, 曽我部共生, 鈴木啓太, 笠井亮秀, 山下洋, 栗田豊  2014年度水産学会近畿支部例会講演要旨集  p.9  2014/11/22  [Not refereed][Not invited]
  • 由良川河口から丹後海における基礎生産構造
    安佛かおり, 舟橋達宏, 渡辺謙太, 秋山諭, 上野正博, 笠井亮秀, 山下洋  2014年度生物地球化学研究会講演要旨集  2014/10/24  [Not refereed][Not invited]
  • 沿岸性魚類スズキにおける河川・河口域の重要性
    冨士泰期, 鈴木啓太, 上野正博, 笠井亮秀, 山下洋  2014年度生物地球化学研究会講演要旨集  2014/10/24  [Not refereed][Not invited]
  • Relative contribution of estuarine nursery areas to the adult population of the temperate seabass Lateolabrax japonicus in Tango Bay, as revealed by otolith Sr:Ca ratios、口頭
    Taiki Fuji, Akihide Kasai, Masahiro Ueno, Yoh Yamashita  5Th International otolith symposium. 要旨集  p.12  2014/10  [Refereed][Not invited]
  • 異なる河川におけるスズキ稚魚の摂餌生態と成長〜下流域におけるアミ類の分布と稚魚の摂餌〜 口頭
    桑原卓哉, 冨士泰期, 鈴木啓太, 笠井亮秀, 山下 洋, 岩本有司, 小路 淳  平成26年度日本水産学会秋季大会講演要旨集  p.79  2014/09/20  [Not refereed][Not invited]
  • 由良川下流から河口域における基礎生産 口頭
    安佛かおり, 舟橋達宏, 石井健一郎, 笠井亮秀, 上野正博, 山下 洋  日本陸水学会 第79回大会講演要旨集  p.90  2014/09/10  [Not refereed][Not invited]
  • 東北海域におけるホシガレイ仔稚魚の採捕記録と成長
    和田敏裕, 有瀧真人, 冨山毅, 中山耕至, 鈴木啓太, 笠井亮秀, 山下洋, 田中克  平成26年度日本水産学会秋季大会講演要旨集  p.80  2014/09  [Not refereed][Not invited]
  • 由良川河口域におけるスズキ稚魚の摂餌生態と餌環境（口頭発表）
    冨士泰期, 笠井亮秀, 上野正博, 山下 洋  平成26年度日本水産学会春季大会  p.93  2014/03/28  [Not refereed][Not invited]
  • 若狭湾西部海域における一次生産構造の季節変化 （口頭発表）
    舟橋達宏, 笠井亮秀, 鈴木啓太, 上野正博, 山下 洋  平成26年度日本水産学会春季大会  p.137  2014/03/28  [Not refereed][Not invited]
  • スズキ仔稚魚の成長に影響を及ぼす環境要因 （口頭発表）
    笠井亮秀, 青木貴志, 高林長将, 冨士泰期, 舟橋達宏, 栗田豊, 和田敏裕, 日比野学, 山下 洋  平成26年度日本水産学会春季大会  p.92  2014/03/28  [Not refereed][Not invited]
  • 数値実験を用いた由良川河口域の低次生産過程の再現とその考察
    舟橋達宏, 笠井亮秀, 上野正博, 山下 洋  木文化プロジェクト 03年度報告会  2014/03/05  [Not refereed][Not invited]
  • 耳石解析によるスズキ稚魚の回遊生態
    冨士泰期, 笠井亮秀, 上野正博, 山下 洋  木文化プロジェクト 03年度報告会  2014/03/05  [Not refereed][Not invited]
  • 由良川−丹後海における栄養塩・懸濁態有機物の動態と基礎生産構造
    渡辺謙太, 笠井亮秀, 福?康司, 吉岡崇仁, 上野正博, 山下 洋  木文化プロジェクト 03年度報告会  2014/03/05  [Not refereed][Not invited]
  • 由良川河口域における魚類群集と餌生物の季節変動
    青木貴志, 笠井亮秀, 冨士泰期, 上野正博, 山下 洋  木文化プロジェクト 03年度報告会  2014/03/05  [Not refereed][Not invited]
  • 由良川下流域から丹後海における底生動物による有機物利用の空間変動
    Emily S. Antonio, 笠井亮秀, 上野正博, 横山寿, 山下 洋  木文化プロジェクト 03年度報告会  2014/03/05  [Not refereed][Not invited]
  • MIZUTA Darien Danielle, 笠井 亮秀, 石井 健一郎  水産海洋研究 = Bulletin of the Japanese Society of Fisheries Oceanography  78-  (1)  13  -27  2014/02
  • スズキ仔稚魚の成長に関する海域間比較 ‐耳石日周輪解析によるアプローチ‐ （口頭発表）
    青木貴志, 高林長将, 冨士泰期, 舟橋達宏, 栗田 豊, 和田敏裕, 日比野学, 笠井亮秀, 山下 洋  2013年度水産学会近畿支部後期例会  2013/12/07  [Not refereed][Not invited]
  • かわいい子には旅をさせよ 〜スズキの遡河群と沿岸群の初期生活史〜 （口頭発表）
    冨士泰期, 笠井亮秀, 上野正博, 山下 洋  2013年度水産海洋学会シンポジウム  p.125  2013/11/15  [Not refereed][Not invited]
  • スズキ稚魚に対する河川の役割 （口頭発表）
    冨士泰期, 笠井亮秀, 上野正博, 山下 洋  第3回日本海研究集会 日本海の水産資源と環境・地域社会を考えるシンポジウム「みえる水（河川表流水）・みえない水（地下水）を通した陸域と海域のつながり」  2013/11/09  [Not refereed][Not invited]
  • 今井 一郎, 笠井 亮秀, 小路 淳  水産海洋研究 = Bulletin of the Japanese Society of Fisheries Oceanography  77-  39  -45  2013/11
  • Mechanisms of river ascending by juvenile temperate seabass Lateolabrax japonicas ポスター
    Fuji T, Kasai A, Ueno M, Yamashita Y  2013 Global Congress on ICM: Lessons learned to address new challenges, Marmaris, Turkey  2013/11  [Refereed][Not invited]
  • Linkage between coastal phytoplankton production and river discharge in the Yura River Estuary, japan ポスター
    Watanabe K, Kasai A, Fukusaki K, Ueno M, Yamashita Y  2013/11  [Refereed][Not invited]
  • Mechanisms of the river ascent of juveniles seabass
    Fuji T, Kasai A, Ueno M, Yamashita Y  2013/11  [Refereed][Not invited]
  • Standing stocks and productivity of phytoplankton in the Yura River estuary ポスター
    Anbutsu K, Funahashi T, Ishii K, Kasai A, Ueno M, Yamashita Y  2013/11  [Refereed][Not invited]
  • The effect of hydrographic conditions on the primary production in the Yura Estuary, Japan ポスター
    Funahashi T, Kasai A, Ueno M, Yamashita Y  2013/11  [Refereed][Not invited]
  • 弱混合型エスチュアリー由良川における基礎生産構造
    笠井亮秀, 安佛かおり, 舟橋達宏, 石井健一郎, 上野正博, 山下洋  平成25年度日本水産学会春季大会  p.172  2013/03/28  [Not refereed][Not invited]
  • 日本海と瀬戸内海に流入する河川におけるスズキの初期生態比較
    桑原 卓哉, 冨士 泰期, 笠井 亮秀, 山下 洋, 一見 和彦, 岩本 有司, 荻野 裕平, 中野 光, 小路 淳  平成25年度日本水産学会春季大会  p.67  2013/03/27  [Not refereed][Not invited]
  • スズキ稚魚の河川遡上メカニズム - 2．水温との関係
    冨士泰期, 笠井亮秀, 上野正博, 山下洋  平成25年度日本水産学会春季大会  p.67  2013/03/27  [Not refereed][Not invited]
  • スズキ稚魚の河川遡上メカニズム - 1．塩水遡上との関係
    冨士泰期, 笠井亮秀, 上野正博, 山下洋  平成25年度日本水産学会春季大会  p.67  2013/03/27  [Not refereed][Not invited]
  • 由良川河口域における植物プランクトンの基礎生産構造
    安佛 かおり, 舟橋 達宏, 石井 健一郎, 笠井 亮秀, 上野 正博, 山下 洋  日本生態学会静岡大会  p.362  2013/03/06  [Not refereed][Not invited]
  • 杉本亮, 笠井亮秀, 山本圭吾  日本海洋学会大会講演要旨集  2013-  2013
  • 伊藤幸彦, 笠井亮秀, 木村伸吾, 木村伸吾  水産海洋学会研究発表大会講演要旨集  2013-  2013
  • 銭本慧, 伊藤幸彦, 笠井亮秀, 木村伸吾, 木村伸吾  日本水産学会大会講演要旨集  2013-  2013
  • Sugimoto R, Kasai A  Proceedings of the 10th Global Congress on ICM: Lessons Learned to Address New Challenges, EMECS 2013 - MEDCOAST 2013 Joint Conference  2-  777  -784  2013/01/01  [Refereed][Not invited]
     
    The increase in human population in coastal watersheds has increased the delivery of nitrogen from the land to coastal environments. Accelerated nitrogen cycles in coastal environments have led to an increase in hypoxic waters and instances of harmful algal blooms. Physical and biogeochemical processes within estuaries generally regulate nitrogen fluxes from land to sea. The estuaries of major rivers on the continents are thought to be sites of massive nitrate losses. However, function of estuaries to nitrogen transfer must vary according to each estuarine hydrology and biogeochemistry. Osaka Bay is one of the most eutrophic embayments in Japan. A large amount of terrestrial nitrogen empties into the bay head from the Yodo River. Although the estuary would have a crucial role in modifying nitrogen fluxes, its function to nitrogen transfer is still unclear. In this study, we examined concentrations and stable isotope ratios (δ15N) of NO3- in the Yodo River Estuary to clarify the dominant biogeochemical processes on DIN dynamics within the estuary and to assess the effect of function of the estuary on eutrophication in Osaka Bay. Contrastive results were obtained from the observations during spring tides in May 2010 and 2011. Nitrate concentrations were high and δ15N was low when high salinity water (>30) intruded into the estuary in 2010. Most of the δ15N variations within the estuary were expressed by the Rayleigh accumulation model with isotope discrimination of nitrification, suggesting the importance of remineralisation for determinant of DIN concentration within the estuary. However, nitrate concentrations were low and δ15N was high when the high salinity.
  • Akihide Kasai, Tatsuhiro Funahashi, Kaori Anbutsu, Ken-ichiro Ishii, Masahiro Ueno, Yoh Yamashita  GLOBAL CONGRESS ON ICM: LESSONS LEARNED TO ADDRESS NEW CHALLENGES, VOLS. 1 AND 2  807  -816  2013  [Refereed][Not invited]
     
    Estuaries are formed around the river mouths, where lighter fresh water meets denser sea water. Many comparative studies have shown that production in estuaries is highest in marine systems, although there is a great deal of variety in mixing processes and salinity distributions. This study was conducted in the Yura Estuary, which is highly stratified because of the small tide, facing to the Sea of Japan. Seasonal and temporal variety of river discharge affects the dynamics in the estuary; the salt wedge intrudes into the bottom layer in summer when the river discharge is low. Consequent primary production is high in summer and a chlorophyll maximum is generated around the halocline, indicating that the salt wedge plays an important role in the ecosystem in the estuary. A hydrodynamic-ecosystem coupled model was developed to investigate the formation mechanism of the chlorophyll maximum in the subsurface layer in the Yura Estuary. Salinity and chlorophyll distributions obtained by the model agreed well with field observations. The model results shows that in addition to the seasonal variation, the salt wedge responds over short time scales according to the flood events, and consequent distribution of chlorophyll frequently changes. Marine diatoms grow using a plenty of nutrients from the river when the salt wedge is formed in the bottom layer. However, production around the halocline is not always higher than the other layers. Direct measurements of the primary production in the Yura River showed the highest production in the surface layer, supporting the model results. These results indicate that the retention of advected phytoplankton is important for the formation of the chlorophyll maximum in the subsurface layer in the Yura Estuary.
  • 由良川河口域における魚類群集と餌生物の相互関係
    青木 貴志, 冨士 泰期, 笠井 亮秀, 上野 正博, 山下 洋  2012年度水産学会近畿支部後期例会  2012/12/01  [Not refereed][Not invited]
  • 河川はスズキの生育場として重要なのか? −耳石Sr/Caによるアプローチ−
    冨士 泰期, 笠井 亮秀, 上野 正博, 山下 洋  2012年度水産学会近畿支部後期例会  2012/12/01  [Not refereed][Not invited]
  • 由良川河口域における浮遊藻類の分布と一次生産について
    安佛 かおり, 舟橋 達宏, 笠井 亮秀, 上野 正博, 山下 洋  日本陸水学会第77回大会  p.164  2012/09/16  [Not refereed][Not invited]
  • 3つの河川の下流?河口域におけるスズキ仔稚魚の摂餌生態比較
    桑原 卓哉, 一見 和彦, 岩本 有司, 冨士 泰期, 笠井 亮秀, 山下 洋, 荻野 裕平, 中野 光, 小路 淳  平成24年度日本水産学会秋季大会  p.93  2012/09/15  [Not refereed][Not invited]
  • 野々大樹, 笠井亮秀, 山本圭吾, 酒井基介, 林浩志  日本水産学会大会講演要旨集  2012-  2012
  • Influence of river flow on the dynamics of phytoplankton blooms during winter to spring in a micro-tidal estuary: Yura River Estuary, Japan
    Watanab,Kenta, Fukuzaki,Koji, Akiyama,Satoshi, Ichimi,Kazuhiko, Kasai,Akihide, Ueno,Masahiro, Yamashita,Yoh  ECSA 50  2012  [Refereed][Not invited]
  • Relative contribution of the river nursery areas to temperate seabass Lateolabrax japonicus adult population revealed by otolith Sr:Ca ratio.
    Fuji,Taiki, Kasai,Akihide, Ueno,Masahiro, Yamashita,Yoh  50th ECSA (Estuarine Coastal Science Association) Conference  2012  [Refereed][Not invited]
  • Matsuno Takeshi, Kasai Akihide  Bulletin on coastal oceanography  48-  (2)  95  -97  2011
  • 森岡裕詞, 笠井亮秀, 北川貴士, 河村知彦, 木村伸吾  水産海洋学会研究発表大会講演要旨集  2011-  2011
  • Temporal diet shift among benthic communities in a river-estuary-marine gradient
    Antonio,E. S, Ueno,M, Kasai,A, Ishihi,Y, Yokoyama,H, Yamashita,Yoh  Annual Conference of the South African Society of Aquatic Scientists  p.15  2011  [Refereed][Not invited]
  • Use of salt-wedge intrusion by temperate seabass juveniles to ascend to upper estuary areas in the Yura River, Japan
    Fuji,T, Kasai,A, Ueno,M, Yamashita,Yoh  21st Biennial Conference of the Coastal and Estuarine Research Federation  p.73  2011  [Refereed][Not invited]
  • Feeding dynamics of macrobenthic communities from the Yura River-Estuary to Tango Sea
    Antonio,E.S, Ueno,Masahiro, Kasai,A, Ishihi,Y, Yokoyama,H, Yamashita,Yoh  平成23年度日本水産学会春季大会講演要旨集  p.61  2011  [Refereed][Not invited]
  • 由良川河口域における塩水楔の短期変動に関する数値実験
    舟橋 達宏, 笠井 亮秀, 上野 正博, 山下 洋  平成23年度日本水産学会春季大会講演要旨集,  p.60  2011  [Not refereed][Not invited]
  • 笠井亮秀, 山本圭吾, 大美博昭, 佐野雅基, 酒井基介, 住友寿明, 西岡智哉, 岩本俊樹  日本水産学会大会講演要旨集  2010-  112  2010/09/22  [Refereed][Not invited]
  • Land-Sea Connection
    Antonio,E.S, Ueno,M, Kasai,A, Ishihi,Y, Yokoyama,H, Yamashita,Yoh  Key for Management of Estuary-Marine Systems?ECSA 47 Symposium , Book of Abstracts (Estuarine and Coastal Sciences Association)  p.53  -54  2010  [Refereed][Not invited]
  • 京都府由良川河口域におけるスズキ稚魚の河川への回遊と塩水遡上との関係
    笠井亮秀  2010年度水産海洋学会研究発表大会  2010  [Refereed][Not invited]
  • 弱混合域における河川流量と塩水遡上の関係 -数値実験によるアプローチ-
    笠井亮秀  2010年度水産海洋学会研究発表大会  2010  [Refereed][Not invited]
  • Spatial variability of food environment for bivalves in a narrow strait using stable isotope analysis
    Akihide Kasai  International symposium on isotope ecology 2010 in Kyoto: Relationship between biodiversity and ecosystem function  2010  [Refereed][Not invited]
  • 182. Migration and growth pattern of the temperate seabass Lateorabrax japonicus in the Yura River estuary revealed by δ13C
    Akihide Kasai  International symposium on isotope ecology 2010 in Kyoto: Relationship between biodiversity and ecosystem function  2010  [Refereed][Not invited]
  • Land-sea connection: Crucial for management of estuary-marine systems
    Akihide Kasai  Techno-Ocean 2010  2010  [Refereed][Not invited]
  • Early life of the temperate seabass Lateolabrax japonicus
    Akihide Kasai  Techno-Ocean 2010  2010  [Refereed][Not invited]
  • 若狭湾由良川河口域におけるスズキ稚魚の生態
    笠井亮秀  公開シンポジウム森里海連環と地球的課題  2010  [Refereed][Not invited]
  • Land-sea connection: Key for management of estuary-marine systems
    Akihide Kasai  ECSA (The Estuarine & Coastal Sciences Association) 47 symposium  2010  [Refereed][Not invited]
  • 十三湖におけるヤマトシジミ(Corbicula japonica)の減耗要因について
    笠井亮秀  2010年度日本水産学会春季大会  2010  [Refereed][Not invited]
  • 天然水域におけるヤマトシジミの成長要因の解明
    笠井亮秀  2010年度日本水産学会春季大会  2010  [Refereed][Not invited]
  • 河川流量の変動がヤマトシジミの成長に及ぼす影響
    笠井亮秀  河川生態学術研究会第４回岩木川研究グループ発表会  2010  [Refereed][Not invited]
  • Food habits and migration pattern of the Japanese temperate bass Lateolabrax japonicus in the Yura River Estuary
    Akihide Kasai  International Symposium on Integrated Coastal Management for Marine Biodiversity in Asia  2010  [Refereed][Not invited]
  • 笠井 亮秀, 小松 幸生, 佐々 千由紀, 小西 芳信  日本水産學會誌 = Bulletin of the Japanese Society of Scientific Fisheries  75-  (4)  615  2009/07/15
  • 豊原治彦, 土屋佳奈子, 笠井亮秀  日本水産学会大会講演要旨集  2009-  158  2009/03/27  [Not refereed][Not invited]
  • 杉本 亮, 笠井 亮秀  日本微生物生態学会講演要旨集  (25)  44  -44  2009  [Not refereed][Not invited]
  • Cosumption of organic matter by benthic communities determined by stable isotope analysis from downstream of Yura River to offshore of Tango Sea 森と里と海のつながり12． 安定同位対比分析による由良川下流〜丹後海におけるベントスの有機物利用
    Antonio, E.S, Ueno M, Kasai A, Kurikawa Y, Ishihi Y, Yokoyama H, Yamashita Y  2010年度日本水産学会春季大会 講演要旨集  p.157  2009  [Refereed][Not invited]
  • 安定同位体比を用いたスズキ仔稚魚の回遊推定
    冨士 泰期, 笠井 亮秀, 鈴木 啓太, 上野 正博, 山下 洋  2009年度水産海洋学会研究発表大会講演要旨集, p.32  2009  [Not refereed][Not invited]
  • 笠井亮秀  2009年度水産海洋学会研究発表大会  2009-  2009  [Refereed][Not invited]
  • 安定同位体比を用いた伊勢湾への河川起源窒素の負荷量評価
    笠井亮秀  2009年度水産海洋学会研究発表大会  2009  [Refereed][Not invited]
  • 笠井亮秀  2009年度日本海洋学会秋季大会  2009-  2009  [Refereed][Not invited]
  • 笠井亮秀  2009年度日本海洋学会秋季大会  2009-  2009  [Refereed][Not invited]
  • 由良川河口域の物理・化学・基礎生産過程
    笠井亮秀  2009年度日本水産学会春季大会  2009  [Refereed][Not invited]
  • 由良川河口域におけるスズキ仔魚の成長と生残
    笠井亮秀  2009年度日本水産学会春季大会  2009  [Refereed][Not invited]
  • 太田川河口域における魚類生産と餌起源の季節変化～河川・河口・海域の比較～
    笠井亮秀  2009年度日本水産学会春季大会  2009  [Refereed][Not invited]
  • 由良川に生息するメイオベントスのセルラース分解能の検討
    笠井亮秀  2009年度日本水産学会春季大会  2009  [Refereed][Not invited]
  • 由良川河口沿岸域における底生マクロベントスの食物構造
    笠井亮秀  2009年度日本水産学会春季大会  2009  [Refereed][Not invited]
  • 157. 由良川河口沿岸域におけるスズキ稚魚の出現と食性
    笠井亮秀  2009年度日本水産学会春季大会  2009  [Refereed][Not invited]
  • 由良川水系における懸濁態有機物と土地利用との関係
    笠井亮秀  2009年度日本水産学会春季大会  2009  [Refereed][Not invited]
  • 夏季の筑後川の高濁度汽水域における粒状有機物の動態
    笠井亮秀  2009年度日本水産学会春季大会  2009  [Refereed][Not invited]
  • ANTONIO Emily S, KASAI Akihide, UENO Masahiro, WON Nam‐Il, KAWAMURA Tomohiko, ISHIHI Yuka, MUKAI Hiroshi, YOKOYAMA Hisashi, YAMASHITA Yoh  日本甲殻類学会大会講演要旨集  47th-  127  2009  [Refereed][Not invited]
  • 坂本 健太郎, 東畑 顕, 山下 倫明, 笠井 亮秀, 豊原 治彦, 京都大学大学院農学研究科, 独, 水産総合研究センタ, 中央水産研究所, 独)水産総合研究センタ, 中央水産研究所, 京都大学大学院農学研究科, 京都大学大学院農学研究科  日本水産学会誌 = Bulletin of the Japanese Society of Scientific Fisheries  74-  (4)  569  -569  2008/07/15  [Not refereed][Not invited]
  • 笠井亮秀  安定同位体スコープで覗く海洋生物の生態-アサリからクジラまで  46  -57  2008
  • 杉本亮, 笠井亮秀, 宮島利宏, 藤田弘一  日本海洋学会大会講演要旨集  2008-  2008
  • 杉本亮, 杉本亮, 笠井亮秀, 宮島利宏, 藤田弘一  水産海洋学会研究発表大会講演要旨集  2008-  2008
  • 笠井亮秀, 杉本亮, 杉本亮, 宮島利宏, 藤田弘一  水産海洋学会研究発表大会講演要旨集  2008-  2008
  • 森岡裕詞, 木村伸吾, 笠井亮秀  日本水産学会大会講演要旨集  2008-  2008
  • Origin of particulate organic matter in the Yura River, Japan
    Suzuki, K, Sugimoto R, Kasai A, Ueno M, Yamashita Y  EMECS (Environmental Management of Enclosed Coastal Seas)-8, Abstract  p.96  -97  2008  [Refereed][Not invited]
  • Modeling phytoplankton production in Ise Bay, Japan -application of nitrogen isotopes to identification of DIN sources
    Sugimoto,Ryo, Kasai,Akihide, Miyajima,T, Fujita,K  EMECS8 (Shanghai, China)  2008  [Refereed][Not invited]
  • 笠井亮秀  2008年度水産海洋学会研究発表大会  2008-  2008  [Refereed][Not invited]
  • 藻場の魚類生産にもとづく生態系サービスの定量評価の試み－アマモ場におけるメバル仔稚魚の生産速度と餌起源の推定－
    笠井亮秀  2008年度水産海洋学会研究発表大会  2008  [Refereed][Not invited]
  • 安定同位体比を用いた大村湾における食物網解析
    笠井亮秀  2008年度水産海洋学会研究発表大会  2008  [Refereed][Not invited]
  • Isotope evidence of seasonal variation in feeding niche of river and brackish gastropods
    Akihide Kasai  2008 8th EMECS (Environmental Management of Enclosed Coastal Seas) conference  2008  [Refereed][Not invited]
  • Modeling of phytoplankton production in Ise Bay, Japan: application of nitrogen isotopes to identification of DIN sources
    Akihide Kasai  2008 8th EMECS (Environmental Management of Enclosed Coastal Seas) conference  2008  [Refereed][Not invited]
  • Seasonal variation in seawater intrusion and primary production in the Yura Estuary, Japan
    Akihide Kasai  2008 8th EMECS (Environmental Management of Enclosed Coastal Seas) conference  2008  [Refereed][Not invited]
  • Increase in moon jellyfish populations in the Seto Inland Sea, Japan: Possible effect on predator-prey interactions under summer hypoxia
    Akihide Kasai  2008 8th EMECS (Environmental Management of Enclosed Coastal Seas) conference  2008  [Refereed][Not invited]
  • Ecosystem and biological production in Lake Jusan; nutrient cycles and spatiotemporal variability
    Akihide Kasai  2008 5th world fisheries congress  2008  [Refereed][Not invited]
  • Isotopic benthic community structure from downstream to offshore of Yura River
    Akihide Kasai  2008 5th world fisheries congress  2008  [Refereed][Not invited]
  • 笠井亮秀  2008年度 海洋学会春季大会  2008-  2008  [Refereed][Not invited]
  • 炭素・窒素安定同位体比分析及び飼育実験によるアイゴの摂餌選択性の解明
    笠井亮秀  2008年度 海洋学会春季大会  2008  [Refereed][Not invited]
  • 伊勢湾における無機態窒素の挙動と低次生産機構の解明－d15N結合生態系モデルによる低次生産機構の解明－
    笠井亮秀  2008年度 海洋学会春季大会  2008  [Refereed][Not invited]
  • KASAI Akihide, ANTONIO Emily, KURIKAWA Yoshiro, UENO Masahiro, YAMASHITA Yoh  Program Abstr 5th World Fish Congr 2008  250  2008  [Refereed][Not invited]
  • SAKAMOTO Kentaro, SAKAMOTO Kentaro, TOUHATA Ken, KASAI Akihide, TOYOHARA Haruhiko  Program Abstr 5th World Fish Congr 2008  358  2008  [Refereed][Not invited]
  • 笠井 亮秀  水産海洋研究  71-  (4)  299  -301  2007/11/08
  • 小松 幸生, 笠井 亮秀  月刊海洋 = Kaiyo monthly / 月刊海洋編集部 編  39-  (8)  550  -555  2007/08
  • 笠井 亮秀, 豊原 治彦, 中田 晶子, 三浦 常廣, 東 信行, 京都大学農学研究科, 京都大学農学研究科, 京都大学農学研究科, 島根県水産技術センター, 弘前大学農学生命科学部  日本水産学会誌 = Bulletin of the Japanese Society of Scientific Fisheries  73-  (4)  646  -646  2007/07/15  [Not refereed][Not invited]
  • 坂本健太郎, 笠井亮秀, 豊原治彦  日本水産学会大会講演要旨集  2007-  135  2007/03/28  [Not refereed][Not invited]
  • 小松 幸生, 笠井 亮秀  水産海洋研究 = Bulletin of the Japanese Society of Fisheries Oceanography  71-  (1)  53  -55  2007/02
  • 杉本亮, 笠井亮秀, 宮島利宏, 藤田弘一  水産海洋学会研究発表大会講演要旨集  2007-  2007
  • 笠井亮秀, 杉本亮, 宮島利宏, 藤田弘一  水産海洋学会研究発表大会講演要旨集  2007-  2007
  • 杉本亮, 笠井亮秀, 宮島利宏, 藤田弘一  日本海洋学会大会講演要旨集  2007-  2007
  • 杉本 亮, 藤原 建紀, 笠井 亮秀  海洋  39-  (1)  9  -14  2007/01  [Not refereed][Not invited]
  • Causes of the decrease of coastal fishery stocks in Japan, examination from ecological links from forest to coastal waters
    Yamashita,Y, Ueno,M, Kasai,A  International Symposium on Integrated Coastal Zone Management, Book of Abstracts  p.138  2007  [Refereed][Not invited]
  • Formation mechanism of hypoxia in estuarine and coastal seas
    Kasai,A, Kurikawa,Y, Ueno,M, Yamashita,Y  International Symposium on Integrated Coastal Zone Management, Book of Abstracts  p.117  2007  [Refereed][Not invited]
  • 由良川水系における土地利用形態と水質の関係
    鈴木 健太郎, 杉本 亮, 笠井 亮秀, 上野 正博, 山下 洋, 田中 克  平成19年度日本水産学会春季大会講演要旨集, p.240  2007  [Not refereed][Not invited]
  • 由良川水系における懸濁態有機物の挙動
    鈴木 健太郎, 杉本 亮, 笠井 亮秀, 上野 正博, 山下 洋  平成19年度日本水産学会近畿支部後期例会要旨集, p.7  2007  [Not refereed][Not invited]
  • 由良川河口域の物理構造・一次生産構造の解明
    栗川 喜朗, 笠井 亮秀, 上野 正博, 山下 洋  平成19年度日本水産学会春季大会講演要旨集, p.239  2007  [Not refereed][Not invited]
  • 坂本健太郎, 笠井亮秀, 坂上善人, 豊原治彦  日本水産学会大会講演要旨集  2006-  215  2006/03/30  [Not refereed][Not invited]
  • 笠井 亮秀, 京大院農  日本水産学会誌 = Bulletin of the Japanese Society of Scientific Fisheries  72-  (2)  283  -284  2006/03/15
  • 杉本亮, 宮島利宏, 笠井亮秀, 藤田弘一  日本海洋学会大会講演要旨集  2006-  2006
  • 河口域潮下帯のヒトデ類は何を食べているか？
    坂本 三和, 上野 正博, 山下 洋, 笠井 亮秀, 林 勇夫  平成18年度日本水産学会大会講演要旨集, p.106  2006  [Not refereed][Not invited]
  • 豊原治彦, 高木雅哉, 林勇夫, 久保田賢, 東畑顕, 山下倫明, 笠井亮秀  日本水産学会大会講演要旨集  2005-  138  2005/04/01  [Not refereed][Not invited]
  • 有明海産スズキ稚魚の河川遡上生態－安定同位体比からのアプローチ－
    鈴木啓太, 笠井亮秀, 太田太郎, 礒田能年, 中山耕至, 田中 克  2005年度日本水産学会春季大会  2005/03  [Not refereed][Not invited]
  • 餌生物の切り替えによるミズクラゲの炭素および窒素安定同位体比の経時変化
    木村 千秋, 笠井 亮秀, 益田 玲爾, 山下 洋  日本水産学会近畿支部大会講演要旨集  2005  [Not refereed][Not invited]
  • 由良川河口域潮下帯におけるベントスの食物網
    坂本 三和, 上野 正博, 笠井 亮秀, 山下, 林 勇夫  日本ベントス学会講演要旨集  2005  [Not refereed][Not invited]
  • 若狭湾潮下帯ベントスは陸上有機物を食べているか？
    坂本 三和, 上野 正博, 笠井 亮秀, 山下 洋, 林 勇夫  北大-京大-琉大連携フィールド科学シンポジウム要旨集, p.24  2005  [Not refereed][Not invited]
  • 若狭湾2河口域に出現するクラゲ3種の生態特性-安定同位体比分析と胃内容物査定による食性解析-
    木村 千秋, 益田 玲爾, 笠井 亮秀, 上野 正博, 山下 洋, 田中 克  北大-京大-琉大連携フィールド科学シンポジウム要旨集, p.15  2005  [Not refereed][Not invited]
  • 有明海産スズキ稚魚の生態解明への安定同位体比の応用－基礎情報としての濃縮係数と半減期の決定－
    鈴木啓太, 笠井亮秀, 太田太郎, 中山耕至, 田中 克  2004年度日本水産学会春季大会  2004/03  [Not refereed][Not invited]
  • Influence of changes in river discharge on the variation in particulate organic matter in Ise Bay.
    Sugimoto, R, Kasai, A, Yamao, S, Fujiwara, T, Kimura, T  Proceedings of International Symposium on Long-term Variations in the Coastal Environments and Ecosystems  206  -211  2004  [Not refereed][Not invited]
  • 海の栄養、陸の栄養
    笠井 亮秀  瀬戸内海,31, 4-8  2002  [Refereed][Not invited]
  • Modeling the transport and survival of fish eggs and larvae.
    笠井 亮秀  GLOBEC Report,15, 49-51  2002  [Refereed][Not invited]
  • イギリス,ウェールズで沿岸海洋学の研究に携わる
    笠井 亮秀  '99 大学院留学辞典,/,228-229  1999  [Refereed][Not invited]
  • Coastal Oceanography in Wales
    笠井 亮秀  ,/,228-229  1999  [Refereed][Not invited]
  • 木村伸吾, 中田英昭, 岡崎雄二, 笠井亮秀, 杉本隆成  日本水産学会大会講演要旨集  1998-  1998
  • 木村伸吾, 中田英昭, 岡崎雄二, 笠井亮秀, 杉本隆成  日本海洋学会大会講演要旨集  1998-  1998
  • 光永靖, 坂本亘, 荒井修亮, 笠井亮秀  日本水産学会大会講演要旨集  1997-  89  1997/04  [Not refereed][Not invited]
  • 笠井亮秀, 坂本亘, 光永靖, 山本章太郎  日本水産学会大会講演要旨集  1997-  90  1997/04  [Not refereed][Not invited]
  • 笠井 亮秀  海洋と生物,19/3,219-223  19-  (3)  219  -223  1997  [Refereed][Not invited]
  • Transport of eggs and larvae with relation to the variation in sardine stock
    笠井 亮秀  ,19/3,219-223  1997  [Refereed][Not invited]
  • 笠井亮秀, 坂本亘, 光永靖, 山本章太郎  日本水産学会大会講演要旨集  1996-  48  1996/03  [Not refereed][Not invited]
  • 岡崎雄二, 中田英昭, 木村伸吾, 笠井亮秀  日本水産学会大会講演要旨集  1996-  1996
  • バイオテレメトリーによるイナダの遊泳行動解析
    光永 靖, 坂本 亘, 笠井亮秀, 山本章太郎  海洋理工学会 平成8年度春季大会講演要旨集  9  1996  [Not refereed][Not invited]
  • マイワシ資源変動における物理環境の影響とそのモデル化(共著)
    笠井 亮秀  月刊海洋,28/,98-103  1996  [Not refereed][Not invited]
  • Effects of physical environment on the recruitment of sardine
    笠井 亮秀  Kaiyo monthly,28/,98-103  1996  [Not refereed][Not invited]
  • 木村伸吾, 笠井亮秀, 中田英昭, 杉本隆成  日本海洋学会大会講演要旨集  1995-  1995
  • 笠井亮秀, 木村伸吾, 中田英昭, 杉本隆成  日本海洋学会大会講演要旨集  1995-  1995
  • 中田英昭, 岡崎雄二, 笠井亮秀, 木村伸吾  日本海洋学会大会講演要旨集  1995-  1995
  • 笠井亮秀, 木村伸吾, 杉本隆成  月刊海洋  26-  (11)  1994  [Not refereed][Not invited]
  • Intrusion of theKuroshio water into the Kumano-nada and Enshu-nada Seas
    笠井 亮秀  ,26/11,703-707  1994  [Refereed][Not invited]
  • 笠井亮秀, 木村伸吾, 杉本隆成  日本海洋学会大会講演要旨集  1993-  1993

Books etc

  • 笠井亮秀 (Joint work森と海をつなぐ河口域生態系を探る)
    花乱社 2022/02 (ISBN: 9784910038469) 351p
  • 環境DNA 生態系の真の姿を読み解く
    近藤倫生, 笠井亮秀, 清野聡子, 益田玲爾 (Contributor環境DNAを用いた大規模生態系観測の意義と展望)
    共立出版 2021/03
  • 豊かな内水面水産資源の復活のために－宍道湖からの提言
    (Joint workヤマトシジミの好適餌料の推定および数値シミュレーションによるヤマトシジミ浮遊幼生の輸送・生残実験)
    生物研究社 2020/02
  • Connectivity of Hills, Humans and Oceans: Challenge to Improvement of Watershed and Coastal Environments
    KASAI Akihide (Joint editor)
    京都大学出版会 2014
  • 水産海洋学入門
    笠井 亮秀 (Contributor貧酸素現象と青潮)
    講談社サイエンティフィック 2014
  • 海は百面相
    笠井 亮秀 (Contributor魚類の生態を読み解く新たなカギ)
    京都通信社 2013
  • 最新 水産ハンドブック
    笠井 亮秀 (Contributor潮汐流・干満・エスチャリー循環，高次食物連鎖)
    講談社サイエンティフィック 2012
  • 安定同位体スコープで覗く海洋生物の生態
    笠井 亮秀 (Joint work安定同位体比を用いた餌料源の推定モデル)
    恒星社厚生閣 2008
  • 森川海のつながりと河口・沿岸域の生物生産
    笠井 亮秀 (Contributor河口・沿岸域での陸上有機物の挙動)
    恒星社厚生閣 2008
  • Frontier Science Series No.48 (FSS-48)
    SUGIMOTO Ryo, KASAI Akihide (Joint workChanges in natural isotopic composition of nitrate during the development of hypoxia in Ise Bay, Japan)
    Universal Academic Press 2007
  • 栽培システム学
    笠井 亮秀 (Contributorアジアの栽培システム（水産業）)
    朝倉書店 2005
  • 水産海洋ハンドブック
    笠井 亮秀 (Contributor海水の物性)
    生物研究社 2004
  • Oceanography
    笠井 亮秀 
    , 2000
  • 海洋学
    笠井 亮秀 
    2000大学院留学ガイド(]G0027[)環境学〜海外の環境学プログラム, 2000
  • 黒潮・親潮混合域におけるマイワシ稚仔魚の輸送と生残(共著)
    笠井 亮秀 
    海洋生物の初期ステージにおける生き残り戦略, 1996
  • Transport and survival of Japanese sardine larvae in the Kuroshio-Oyashio region -A numerical approach-
    笠井 亮秀 
    Survival strategies in early life stages of marine resources, 1996

Presentations

  • 環境DNAによるニホンウナギの分布域の推定  [Not invited]
    笠井亮秀, 定行洋亮, 高田真悟, 安孝珍, 山崎彩, 久米学, 寺島佑樹, 東信行, 亀山哲, 木村伸吾, 山中裕樹, 益田玲爾, 山下洋
    2018年度水産海洋学会研究発表大会  2018  東京大学大気海洋研究所  水産海洋学会
  • 水温と塩分がニホンウナギの環境DNA放出量に及ぼす影響  [Not invited]
    高田真悟, 高橋さやか, 益田玲爾, 笠井亮秀
    2018年度水産海洋学会研究発表大会  2018  東京大学大気海洋研究所  水産海洋学会
  • 環境DNA濃度の定量データと流動モデルの統合による個体数・生物量の推定  [Not invited]
    深谷肇一, 村上弘章, 尹錫鎭, 南憲吏, 長田穣, 山本哲史, 益田玲爾, 笠井亮秀, 宮下和士, 源利文, 近藤倫生
    第１回環境DNA学会東京大会  2018  日本科学未来館  環境DNA学会
  • Evaluation of the fish distribution and their environmental DNA in a semi-closed bay using a three-dimensional tracer model  [Not invited]
    Seokjin Yoon, 笠井亮秀, 村上弘章, 南憲吏, 益田玲爾, 宮下和士, 源利文, 近藤倫生
    第１回環境DNA学会東京大会  2018  日本科学未来館  環境DNA学会
  • 環境DNA調査によるニホンウナギの淡水域分布特性の解明  [Not invited]
    定行洋亮, 山中裕樹, 山下 洋, 久米 学, 山崎 彩, 笠井亮秀
    平成30年度日本水産学会春季大会  2018  東京海洋大学  日本水産学会
  • 舞鶴湾におけるマアジとカタクチイワシの環境DNA量の水平・鉛直分布  [Not invited]
    村上弘章, 山本哲史, 源 利文, 南 憲吏, 宮下和士, 深谷 肇一, 尹 錫鎭, 笠井亮秀, 澤田英樹, 鈴木啓太, 益田玲爾, 山下 洋, 近藤倫生
    平成30年度日本水産学会春季大会  2018  東京海洋大学  日本水産学会
  • 東部瀬戸内海における基礎生産構造  [Not invited]
    安佛かおり, 宮原一隆, 山本圭吾, 秋山諭, 笠井亮秀
    第65回日本生態学会大会  2018  札幌コンベンションセンター  日本生態学会
  • 由良川における河口域生態系研究から筑後川研究への展望I  [Not invited]
    有明海森里海連環再生研究会  2010
  • 川の流れに支配される十三湖の生態系  [Not invited]
    河川生態学術研究会第5回岩木川研究グループ研究発表会  2010
  • アサリやシジミは水をきれいにしているのか？－安定同位体比分析による二枚貝の食性解析－  [Not invited]
    2010. 第41回放射線科学研究会  2010
  • 十三湖におけるヤマトシジミの成長要因の解明  [Not invited]
    平成20年度河川生態学術研究会岩木川グループ発表会  2009
  • Removal of terrestrial organic matter by bivalves estimated from stable isotope analysis  [Not invited]
    2008 University of Hawaii and University of Tokyo Joint Symposium on Ocean and Coastal Sciences  2008
  • 陸棚域から伊勢湾への外海起源窒素の流入過程  [Not invited]
    杉本亮, 杉本亮, 笠井亮秀, 宮島利宏, 藤田弘一
    水産海洋学会研究発表大会講演要旨集  2008
  • 安定同位体比を用いた陸棚域における硝酸態窒素の起源推定  [Not invited]
    笠井亮秀, 杉本亮, 杉本亮, 宮島利宏, 藤田弘一
    水産海洋学会研究発表大会講演要旨集  2008
  • Nutrients, chlorophyll and suspended solids from three rivers into Hakodate Bay, Hokkaido, Japan  [Not invited]
    A. Kasai, R. Sugimoto, N. Itoh, K. Tsukagawa, K. Todate
    ECSA 57  Pan Pacific Perth, Australia  Estuarine Coastal Sciences Association

Association Memberships

  • EAST ASIA EEL SOCIETY   瀬戸内海研究会議   日本海洋学会沿岸海洋研究部会   THE eDNA SOCIETY   JAPANESE SOCIETY OF FISHERIES OCEANOGRAPHY   THE JAPANESE SOCIETY OF FISHERIES SCIENCE   THE OCEANOGRAPHIC SOCIETY OF JAPAN   

Works

  • 海洋生物資源の変動要因の解明と高精度変動予測技術の開発
    2002 -2004

Research Projects

  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
    Date (from‐to) : 2022/04 -2025/03 
    Author : 笠井 亮秀, 野村 大樹
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)
    Date (from‐to) : 2021/04 -2025/03 
    Author : 木村 伸吾, 笠井 亮秀, 萩原 聖士, 脇谷 量子郎
     
    [輸送分散過程の数値シミュレーション解析] 主にEUのCopernicusが開発したデータ(GLOBAL OCEAN PHYSICS REANALYSIS)を使用して、オオウナギ北太平洋集団の産卵場（西マリアナ海嶺南部海域）からの仔魚輸送分散シミュレーションを実施した。その結果、北赤道海流によって西方に輸送された後、黒潮に取り込まれて北上するものとミンダナオ海流に取り込まれて南下する輸送経路を再現し、両者の割合には季節的・経年的変動があることを明らかにした。 [ニホンウナギとオオウナギを対象とした成魚の行動調査および人工構造物の影響評価] 養殖ニホンウナギの放流後の行動を調べるために、養殖ウナギ170個体を静岡県の深田川に放流した。携帯型RFIDシステムを用いて経時的追跡調査を実施したところ、上流移動が落差によって制限されることや、肥満度が低いほど下流移動確率が高まることが示された。また、静岡県の道龍川で採集したニホンウナギ49個体と奄美大島の大棚川で採集したオオウナギ106個体の水系内移送放流を行い、経時的追跡調査を実施した。その結果、10日後の元の生息地への回帰率はニホンウナギの場合には上流移送群が29.2%、下流移送群が16.0%、オオウナギの場合には上流移送群が3.7%、下流移送群が36.5%であり、種特異的な生息地固執性・選好性の存在が示唆された。 [環境DNA分析のための採水・濾過および解析] 日本産ウナギ属魚類4種を対象に、環境DNA検出/定量用の種特異的プライマー・プローブセットを設計した。房総半島、屋久島、奄美大島、石垣島、西表島の20河川、計51地点において採水を行い、試料を収集した。また、南西諸島海域で行った学術研究船「白鳳丸」による調査データの遺伝子解析を継続して実施し、その際に採集した仔稚魚の種同定結果との比較を行う準備を進めた。
  • 日本学術振興会：科学研究費助成事業 基盤研究(A)
    Date (from‐to) : 2017/04 -2021/03 
    Author : 笠井 亮秀, 東 信行, 益田 玲爾, 山下 洋, 山中 裕樹, 亀山 哲, 木村 伸吾
     
    本研究では，環境DNAを用いて，日本全国の河川において，絶滅危惧種に指定されているニホンウナギの分布を確定し，そのバイオマスを推定することを目的としている。
    今年度も，昨年度に引き続き，全国の河川下流～河口域において採水を行った。2019年度は，167ヶ所で採水した。環境条件として，水温，電気伝導度，川幅，河口からの距離も同時に測定した。採水サンプルから水中有機物のDNAを抽出し，2017年度に作成したニホンウナギの種特異的プライマーを用いてDNA分析を行った。環境DNAの分布と環境条件との関係を解析したところ，日本国内の河川におけるニホンウナギの分布やバイオマスは，ほぼ仔魚期の輸送環境によって決まることが分かった。そこで産卵場から卵稚仔の輸送をシミュレーションしたところ，地球温暖化に伴って将来日本へのウナギ仔魚の輸送が減少する可能性も示唆された。 また堰が存在する河川においては堰の上流側と下流側で採水とウナギのサンプリングを行い，環境DNAを分析した。その結果，堰がニホンウナギの遡上を妨げており，その分布に影響を及ぼしていることが明らかとなった。特に200mm以下の小型の個体は，堰が増えるにつれその上流側で個体数が有意に少なくなり，小型個体は堰を超えて遡上しづらい状況にあることが分かった。 上記に加えて，環境DNAの分解に関する実験を行った。ウナギを10℃～30℃ の5つの水温区に保った水槽に入れて飼育したのち，水槽から水を取り出し6日間保管した。その間，毎日環境DNA濃度を測定した。その結果，環境DNA濃度の減衰率kと水温Tとの関係はk = 0.02T + 0.18で表され，水温が高いほど分解率が速いことが分かった。
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2016/04 -2020/03 
    Author : Yamashita Yoh
     
    We studied environments and ecosystems which support the production of Japanese eels at a watershed level and examined river restoration measures from the viewpoint of biological production of eels in 8 rivers in Japan. The prey items of eels varied depending on body size, area, and season, but eels consumed a wide range of prey items and showed a flexible feeding ecology. Their favorable microhabitat environments were identified being different between elver phase and yellow phase eels. The movement of eels from the river mouth to upstream was obstructed by weirs. The acceptable range of water quality for this species is broad so that eels can inhabit from clear streams to eutrophicated urban rivers. It was revealed that environmental conditions in rivers which allow movement of eels within rivers and also between river and coastal waters, available habitats as refuges, and sufficient productivity of prey organisms, would lead to restoration and augmentation of Japanese eel stocks.
  • 環境DNA分析に基づく魚類群衆の定量モニタリングと生態系評価方法の開発
    Japan Science and Technology Agency：CREST
    Date (from‐to) : 2013 -2018 
    Author : Michio Kondo
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2014/07 -2017/03 
    Author : Yamashita Yoh
     
    Katsura River had high dissolved nutrients mainly from the rich forests in the catchment area. The high nutrients originated from forests were thought to contribute to high biodiversity and high biological production of fishes such as juvenile seabass and Japanese eel through diverse food web structures in the river. Forests also had function to reduce discharge of harmful small particle <30μm to river ecosystems. Local people in the study area which was recognized as the Globally Important Agricultural Heritage Systems (GIAHS) by FAO in 2013 perform a traditional fishery called Ishi-kura fishing method in estuaries. Ishi-kura is an underwater pile of approximately 0.5 tons of stones 20-30 cm in diameter and wild eels dwell inside the pile and caught using nets. We found that Ishikura plays an important cultural role which connects nature and local residents in GIAHS in addition to providing habitats for newly recruited young eels and their prey animals.
  • 沿岸海域複合生態系の変動機構に基づく生物資源生産力の再生・保全と持続的利用に関する研究
    文部科学省：国家基幹研究開発推進事業 海洋資源利用促進技術開発プログラム
    Date (from‐to) : 2011 -2017 
    Author : 渡邊 良朗
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2010/04 -2014/03 
    Author : NAKATA Hideaki, MATSUOKA Kazumi, UMEZAWA Yu, WADA Minoru, KASAI Akihide, YAMAGUCHI Hitoshi, SUGIMOTO Ryou
     
    Environmental restoration experiments using aeration combined with coastal bioremediation have been conducted in Omura Bay, an enclosed bay being suffering from hypoxia formation in the bottom water every summer, as a model area. Monitoring of nutrients, red-tide outbreaks, and microbial activities related to oxygen consumption has been made in parallel with the monitoring of hypoxia formation in the bottom water. The effectiveness of the restoration was synthetically evaluated and a practical plan for restoring sustainability and autonomous regulation of the Omura Bay ecosystem was newly proposed. Following our proposal, Nagasaki Prefecture will start practical field experiments in Omura Bay from the fiscal year 2014 as a part of the Action Plan for Environmental Conservation and Regional Promotion of Omura Bay.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2009 -2012 
    Author : YAMASHITA Yoh, KASAI Akihide, TOMINAGA Osamu, MATSUISHI Takashi, SHOJI Jun
     
    In order to develop methods to estimate the carrying capacity of commercially important coastal fish nursery grounds, we built two models based on field data important to the production of temperate sea bass and Japanese flounder juveniles. We examined the ecosystem for hydrodynamics, nutrients, primary and secondary production in the Yura River Estuary and Tango Sound and built a hydrodynamics-primary production model (Delft3D) and an ecosystem model (Ecopath)
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2009 -2011 
    Author : TOYOHARA Haruhiko, KASAI Akihide, KAMITAKAHARA Hiroshi
     
    To determine the process of cellulose degradation in mangrove estuaries of the South-Western Islands, Japan, the cellulase activity of sediments was examined at a total of 9 sites on Okinawa Main Island (the River Gesashi and Manko), Ishigaki Island (Nagura Gulf and River Miyara), and Iriomote Island (rivers Urauchi, Mare, Hinai, Shira and Maira). Zymographic analysis was used to record cellulase activity in all sediment samples and in the meiobenthos. A 27-kDa cellulase activity band was expressed by several animal groups examined in the meiobenthos, including Gammaridea, Turbellaria, Ostracoda, Oligochaeta, Nematoda, and Polychaeta. However, the mangrove whelk, Terebralia palustris, which is a widely distributed member of the macrobenthos in these areas except Okinawa Main Island, expressed cellulase activities at 29, 31, 49, and 56 kDa. Interestingly, 31-kDa cellulase activity levels were recorded both in sediments and in the feces of T. palustris. The results of this study indicate that various benthic animals contribute to cellulose degradation in mangrove sediments of estuaries in the Southwestern Japanese Islands.
  • 日本学術振興会：科学研究費助成事業
    Date (from‐to) : 2008 -2010 
    Author : 東 信行, 佐原 雄二, 笠井 亮秀, 和田 実
     
    1)水路網内の移動履歴追跡 個体標識および個体の分布パターンの季節変化など,従来型の方法を用い,調査地区内の魚類の移動パターンを想定した。その結果,特定の支水路が産卵場である可能性が示唆されたため,採集ポイントを定め支水路と幹線水路での採捕を行ない,サンプルを収集した。今年度は炭素・窒素同位体の分析に加えて、筋肉・肝臓の微量元素分析を行った。28元素を定量化し、生息地ごとの分別が可能であるか判別分析を行った。窒素炭素安定同位体では分別できない場合でも、複数の元素を用いて判別分析を行うことにより、ほぼ100%の分別が可能となった。また,クラスター分析を行うことにより,個体レベルの移動履歴を判別することが可能となった。 2)ため池・ダム湖・その他の環境における分別 1)同様に、水路網につながる、溜池やダム湖内でも生息地点による違いが検出できるかサンプルを収集した。この結果、同位体によって分別できない場合においても、90%以上の分別が可能になり、なおかつその要因が推定できる結果となった。ダム湖では,流入河川毎に異なる特徴が現れ,生息地や出生河川などの判別が可能となることが示された。また同様の手法の発展性について,昆虫や鳥類のサンプルも同時に分析を試みその有用性が示された。
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2006 -2008 
    Author : KASAI Akihide, SHOUJI Jun
     
    フィールド調査の結果、ミズクラゲ重量と底層の溶存酸素濃度の間に負の相関が認められた。またミズクラゲの分布域と、魚卵稚仔や動物プランクトンの分布域は、一致していなかった。安定同位体比分析より、ミズクラゲは魚卵稚仔を含む動物プランクトンを主な餌とする雑食性であると推定された。ミズクラゲは強い貧酸素耐性を有しており、沿岸域の 貧酸素化にともない、ミズクラゲへの栄養フローが増大していると推定される。
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2006 -2008 
    Author : KIMURA Shingo, KASAI Akihide, MORIOKA Hiroshi, SIMPSON John, WILES Phil, JONES Gwynne, POWELL Ben
     
    乱流混合が強い英国メナイ海峡域の干潟では、外部からの浮遊性植物プランクトンの流入よりも底生珪藻による基礎生産が大きく、また、底生生物であるヨーロッパイガイ(ムール貝)は底生珪藻と懸濁態有機物を主要な餌資源とする可能性が示された。しかし、ムール貝は懸濁態有機物中のデトライタスを餌として積極的に利用することはなく、その成長には底生珪藻の寄与が極めて大きいことが分かった。結論として、従来考えられてきた外部からの浮遊性植物プランクトンの流入が、高いムール貝の資源量を維持しているのではなく、乱流混合に伴う底生珪藻の生産が重要であることが明らかになった。
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2006 -2008 
    Author : YAMASHITA Yoh, UENO Masahiro, KASAI Akihide, YOSHINAGA Ikuo, TOMINAGA Osamu
     
    沿岸域における魚介類生産は、陸から河川により輸送される栄養物質で支えられている。森で生産された木の葉や枝などの分解されにくい有機物も、河川に住む水生動物は分解酵素を持つことにより有効に利用した。しかし海では、陸からの有機物を直接利用できる動物は多くなく、陸域起源有機物の多くは微生物などの分解を経て無機化され、植物プランクトンなどから始まる新しい生産系に入ることがわかった。一方、陸域起源有機物からゴカイやアミ類を通してスズキ稚魚やヒラメ稚魚に至る食物網が確認された。
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2006 -2008 
    Author : TANAKA Masaru, YAMASHITA Yoh, KASAI Akihide, NAKAYAMA Kouji, SHIRAYAMA Yoshihisa, FUKAMI Hironobu, OHTSUKA Susumu, HARAGUCHI Akira
     
    有明海特産稚魚の存続に不可欠な筑後川の低塩分高濁度汽水域に存在する大陸沿岸遺存生態系の実体解明を, 主として炭素窒素安定同位体比を用いて試みた. その特異な生態系の起源が現存すると推定された韓国西岸群山に流入する錦江河口域において筑後川と同様の調査を行い, 両者を比較した. いずれの河口域においても河川からの淡水流入量や流入パターンが極めて重要な役割を果たしていることが明らかになった.
  • 日本学術振興会：科学研究費助成事業
    Date (from‐to) : 2002 -2004 
    Author : 笠井 亮秀
     
    ヤマトシジミの餌資源を特定することは,資源管理,水質環境保全の両面から意義深いものと考えられる.最近の研究により,河口域に生息するヤマトシジミはあまり餌の選択を行わず,上流側に生息する個体ほど陸上有機物を多く同化することが明らかとなっている.しかし汽水湖に生息するヤマトシジミの食性についてはよく分かっていない.本研究では,小川原湖,十三湖,宍道湖のヤマトシジミの餌資源を安定同位体比分析から推定し,河川棲のヤマトシジミと比較した. 観測は,2004年7月16〜21日,7月21〜25日,8月2〜5日にそれぞれ小川原湖,十三湖,宍道湖で行った.湖内の複数点においてヤマトシジミと水を採取し,水温,塩分,クロロフィル濃度の測定を行った.そして,採取したヤマトシジミ,底生珪藻と水中の粒状有機物について安定同位体比分析を行った. 得られたヤマトシジミの同位体比について判別分析を行った結果,小川原湖,十三湖は大きく2つのグループに分けられ,宍道湖は3つのグループに分けられた.いずれの湖においても,流入河川に近いヤマトシジミほど同位体比が低くなり,特に十三湖ではその傾向が顕著であった.同位体比を基にヤマトシジミの餌資源の寄与率を求めたところ,十三湖の一部を除いて植物プランクトンの寄与率が6割以上と高かった.クロロフィル濃度は,小川原湖と宍道湖では流入河川より明らかに高かったが,十三湖では河川とほぼ同程度であった.また,塩分から河川水の平均滞留時間を見積もると,小川原湖で366日,十三湖で2日,宍道湖で87日となった.すなわち十三湖では,河口域同様水の入れ替わりが速く植物プランクトンの生産がおさえられているため,ヤマトシジミは陸上有機物を多く摂取せざるを得ない.一方,小川原湖や十三湖では水が滞留することで植物プランクトンが豊富に発生し,それがヤマトシジミの餌資源となっていると考えられる.
  • 日本学術振興会：科学研究費助成事業
    Date (from‐to) : 2000 -2001 
    Author : 笠井 亮秀
     
    従来,内湾域において貧酸素水塊は底層に形成されるとされてきたが,中層に形成される場合もある.その違いは,外洋系水の進入深度によって起きる.伊勢湾の場合,外洋系水は伊良湖水道で混合されるので,酸素を豊富に含んでいる.この外洋系水が中層に進入する時は底層に貧酸素水塊ができ,底層に進入する場合は貧酸素水塊が中層に浮き上がる. 進入深度は湾口部と湾内の海水密度の差異によって決まる.そのため,その差異が変化すれば,進入進度も変化する.伊勢湾では,冬季は伊良湖水道の海水の密度が湾内底層の密度よりも大きいので,底層進入となる.一方夏季にはその逆の密度分布となることが多く,外洋系水は中層に進入することが多い.また,伊良湖水道の海水の密度は湾外の海水の影響を受けているため,黒潮の離接岸などによる年毎の変動も大きい.さらに小潮時には伊良湖水道での鉛直混合が若干弱くなるため,下層の密度が湾内底層の密度よりも大きくなり,夏季でも底層進入となる.このような進入進度の変化に伴って,貧酸素水塊も湾奥に押しやられたり中層に浮上したりするなど,短期間のうちに水平・鉛直的な位置が変化する. 伊勢湾の幅は約30kmとロスビーの内部変形半径よりも大きいため,湾内の流れには地球自転の効果が影響を及ぼす.そのため,中層に流入する外洋系水は,愛知県側に押しやられる.その結果三重県側の下層が海水交換から取り残される形になり,低温のドームができ,貧酸素化する. 診断モデルを用いて湾内の密度構造や流れを3次元的に再現するとともに,粒子追跡を行い外洋系水の進入状況を調べた.1986年のように貧酸素化が激しかった年には外洋系水の湾内底層への流入が弱かったため,低温・高密度の海水が湾内下層に広く分布していた.一方比較的酸素濃度が高かった1988年にはエスチュアリー循環によって外洋水が湾内下層に進入し,海水交換が促進される傾向にあった.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 1997 -1999 
    Author : NAKATA Hideaki, KASAI Akihide, KIMURA Shingo
     
    In this study, we aimed to explore how and to what extent meso-scale oceanographic features affect larval growth and survival of small pelagic fishes such as anchovy in the Kuroshio and Kuroshio-Oyashio transitional regions, where major spawning and nursery habitats were located. For this purpose, focusing on the meso-scale eddies caused by frontal disturbances of the Kuroshio and Kuroshio Extension, we made intensive field surveys in addition to detailed analyses of existing data. Numerical bio-physical models for evaluating the effect of meso-scale eddies on the biological production in relation to larval growth/survival were also developed. It has been revealed that warm water regions associated with the northward expansion of the Kuroshio water as seen in the northern edge of the Kuroshio front apparently play an important role in biological production and larval growth/survival of anchovy and other small pelagic fishes. In particular, meso-scale eddies caused by frontal disturbances in these regions contribute greatly to the enhancement of larval food production in addition to entraining and accumulating small-sized larvae into the edge of the eddies. On the other hand, larval growth is appreciably low in less productive Kuroshio water to the south and cold water associated with Oyashio water to the north. Therefore, possibility of the encounter of larvae with meso-scale eddies could determine the extent of larval survival in the offshore water.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 1996 -1997 
    Author : SAKAMOTO Wataru, KASAI Akihide, ARAI Nobuaki
     
    Trace element in fish otoliths were analyzed in 1996 to estimate the life histories of fish in derectly. In 1997, we tried to measure life histories of fish directly by means of micro-data tags in parallel with trace element analysis. The results of trace element analysis indicated that most available element is Sr in salmon otolith. This element especially available to understand the temporal period of salmon when swimming down to the sea side from river or swimming up from the sea to river to spawn, since Sr soncentration in sea water is higher 100 time than the fresh water. And Sr concentration in the otolith is directly influenced by the concentration in environmental water. The micro-data tag experiment was carried out using young yellow tail fish in the period of October and November at the Sagami Bay in 1997. The 12 tags were recovered from the experimental fish and analyzed their data.
  • 日本学術振興会：科学研究費助成事業
    Date (from‐to) : 1996 -1996 
    Author : 笠井 亮秀
     
    黒潮フロントの蛇行に伴う低気圧性渦は,マイワシ等の稚仔魚あるいはその餌生物の輸送や分布に大きな影響を及ぼしている.また黒潮フロント付近は生産性が高く稚仔魚にとって好都合な海域となっている.しかしこの低気圧性渦に対応した生物の分布・動態・生産性については,よく理解されていない.そこで本研究では,1994年5月に遠州灘の黒潮前線域における低気圧性渦を観測した結果に基づいて数値実験を行い,現実の海洋でどの様に植物プランクトン量,栄養塩濃度,水温運動エネルギーが変化するかを再現し,渦の発生に伴う生物生産量を定量的に堆定した. 生物の基礎方程式は,クロロフィル濃度,植物プランクトン内窒素濃度,海水中の硝酸・亜硝酸態窒素濃度から構成されている.また物理モデルとしては,鉛直一次元モデルを用い,鉛直拡散係数はturbulent closureモデルから決定した. モデルを用いて数値実験を行った結果,渦が形成されてから4日目にそれまで一定であった植物プランクトンの増殖率が急速に減少すると共に,植物プランクトン内窒素濃度が最大となった.そして5日目にはクロロフィル濃度が最大値に達した.これらの結果は観測から求められた結果とよく一致している.また,海水中の硝酸態窒素濃度が1μM以下になった時点で増殖率は急速に低下したが,クロロフィル濃度はそれとは時間差を持って急速に減少していることから,植物プランクトンが二次生産を伴う捕食や沈降にまわされていることが分かった.またこれらの時間スケールとして渦が生成されてから約1週間弱で1サイクルの現象が終了することも,観測結果と一致する.この低気圧性渦による基礎生産量を見積もると,40gCm^<-2>y^<-1>となり,過去に推定された遠州灘沿岸域全体での基礎生産量の20〜30%を担っていると考えられる.
  • 日本学術振興会：科学研究費助成事業
    Date (from‐to) : 1995 -1995 
    Author : 笠井 亮秀
     
    海洋環境の変動に対応したブリの回遊行動を調べる実験を,1995年10月から11月にかけて相模湾において行った. 1.超小型超音波発信器(ピンガー)を用いた実験 まず,1日以下のブリの行動を詳細に探るために,ピンガーをブリの背中に取り付け,約20時間追跡した.用いたピンガーは水温と水深を測定し,3秒間隔でデータ値を発信するもので,船上の受信器でデータをキャッチできる仕組みになっている.船の位置をGPSシステムにより確定することにより,水平移動も同時に調査できる. 水平行動に関しては,放流直後ブリは約1時間迷走したが,その後瀬に付き,昼間はその瀬の周辺に留まっていた.日没後急に移動し始め,約5km離れた人工漁礁に付いた後は夜明けまで漁礁から離れなかった.鉛直移動については,昼間は20〜40m深を活発に遊泳し,索餌を試みていたようである.ところが,夜間はほとんどの時間を10m以浅で過ごしていた.その一方で,1時間に数回約40mにまで達する急激なダイビングを見せた. 2.メモリー内蔵型超小型測定器(データロガー)を用いた実験 数日以上の長期にわたるブリの行動を調べるために,データロガーをブリの背中に取り付け,放流した.用いたデータロガーは水温または水深を測定し,20分毎にメモリーにデータを保存できるもので,回収後そのデータをパーソナルコンピュータにより解析できる.放流した3尾のうち,2個体が約2週間後に相模湾内で再捕された. 約2週間のうち2度ほど低気圧の通過により水温が急激に降下したが,それに伴ってブリは平均遊泳水深を変化させたり,鉛直移動の回数を変化させるなど,その行動は明らかに変化した.一方,潮汐や降雨に伴う塩分や濁度の変化に対しては特別な行動の変化は見られなかった.また,ピンガーを用いた実験同様,昼間活発に行動し夜は海表面近くで留まるという明らかな昼行性が確認できた.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 1993 -1994 
    Author : SAKAMOTO Wataru, KASAI Akihide, ARAI Nobuaki, FUJIWARA Tateki
     
    Migration behavior of loggerhead turtles was recorded using microdata tags during internesting. A tag was able to record diving depth and duration, experienced water temperatures, stomach temperatures and underwater irradiance during internesting periods while the turtles swam around the nesting beach. The data were analyzed after tags recovery from the turtles. We could find that turtles neither ate food nor swam off the beach during internesting periods, which were analyzed by means of the diving records and tracking trajectries of ARGOS system. They maintained always higher body temperatures than ambient water temperatures. Underwater irradiance and water temperature records indicated that they did not accept effective heat supply from the solar irradiance energy to maintain high body temperatures. The phenomenon to keep high body temperature was able to analyze using mathematical dynamic heat transfer model with two parameters ; an heat diffusivity and a body mass. We could find the critical sex determination period of newly hatched out turtles. The temperature dependent sex was determined in the period between 23 to 26 developmental stage of eggs.
  • 安定同位体による海域生態系の解明
  • 内湾域の流動構造
  • 内湾、沿岸海域における生物生産環境
  • 浮魚の再生産におよぼす卵稚仔輸送の影響
  • Ecosystem in the Ocean examined by stable istope analysis
  • Flow pattern in estuaries
  • Biorogical production and physical environment in coastal waters
  • The effect of egg and larval transport on the recruitment of Pelagic fish

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