Researcher Database

SAITOH Sei-Ichi
Arctic Research Center
Research Fellow

Researcher Profile and Settings

Affiliation

  • Arctic Research Center

Job Title

    Research Fellow

URL

Research Interests

  • Fisheries Oceanography   Satellite Oceanography   Marine Ecology   

Research Areas

  • Earth and planetary science / Meteorology/Physical oceanography/Hydrology
  • Basic biology / Ecology/Environment
  • Fisheries science / General fisheries

Academic & Professional Experience

  • 2015/04 - Today    Hokkaido UniversityArctic Research CenterDirector

Education

  •        - 1975  Hokkaido University  Faculty of Fisheries
  •        - 1981  Hokkaido University  Graduate School, Division of Fisheries

Research Activities

Published Papers

Books etc

  • Prospects for the Application of Satellite Remote Sensing Data in Fisheries Oceanography
    ()
    Fisheries and Fisheries Oceanography in the Coming Century 1988
  • Technology and Application of Thermal Infrared Remote Sensing
    ()
    Kajima Press 1986
  • Introduction to Remote Sensing
    ()
    Japan Survey Association 1992
  • SST structure of the Polor Front in Japan Sea(jointly worked)
    ()
    Oceanography of Asian Marginal Seas(Elsevier Science Publishers) 1991
  • An application of NOAA AVHRR for Oceanography in the East China Sea(jointly worked)
    ()
    Ocean Hydrodynamics of the Japan and East China Seas(Elsevier Science Publishers) 1984
  • Manual on Survey of Snow and Ice
    ()
    Hokkaido University Press 1991
  • Atmospheric dispersion of volcanic clouds (jointly worked)
    ()
    Remote Sensing of the Oceans(Seibutsu Kenkyusha Co. , Ltd. ) 1993
  • Distribution of mineral aerosols over the North Pacific (jointly worked)
    ()
    Remote Sensing of the Oceans(Seibutsu Kenkyusha Co. , Ltd. ) 1993
  • AVHRR on NOAA(jointly worked)
    ()
    Oceanographic Application of Remote Sensing(CRC Press) 1995
  • OCTS on ADEOS(jointly worked)
    ()
    Oceanographic Application of Remote Sensing(CRC Press) 1995

Conference Activities & Talks

Works

  • Observation of Coastal Front by using Airborne Multi Spectral Scanner(MSS)
    1977
  • Development of On-Line Satellite Information Services using Value Added Network System
    1985 -1987
  • Development and Preliminary Experiment of Sea-Truth Buoy System for ADEOS Satellite
    1993
  • Sea-Truth Observation for Development of Bio-Optical Algorithms in Satellite Ocean Color Remote Sensing
    1994

MISC

Research Grants & Projects

  • Ministry of Education, Culture, Sports, Science and Technology:Grants-in-Aid for Scientific Research(基盤研究(B))
    Date (from‐to) : 2009 -2011 
    Author : Masahide KAERIYAMA
     
    北海道大学The objective of this research is to address the framework of the risk management including the adaptive management and precautionary principle based on the ecosystem through biology of Pacific salmon (Oncorhynchus spp.), which plays an important role as a keystone species in the subarctic ocean and interaction between marine and land ecosystems. Their carrying capacity links with the long-term climate change such as PDO and climate regime-shift, and relates to the density-dependent effect. The residual carrying capacity of chum salmon was positively correlated with body size, while negatively correlated with age at maturity. This indicates the density-dependent effect of hatchery population on growth pattern of wild salmon. On the other hand, the global warming affects growth and survival of juvenile chum salmon. Factors such as the biological interaction between wild and hatchery salmon, the effect of long-term climate change on production trend of Pacific salmon, and the role of anadromous fish on global material circulation suggest that the risk management based on sustainable adaptive management and precautionary principle in ecosystem is a very important consideration for the new fisheries science and the aquatic ecosystem conservation. The risk management based on adaptive management and precautionary principles, is one way to prioritize, identify, and potentially mitigate impacts resulting from diverse human activities in the northern Subarctic aquatic ecosystems.
  • Ministry of Education, Culture, Sports, Science and Technology:Grants-in-Aid for Scientific Research(特定領域研究)
    Date (from‐to) : 2006 -2010 
    Author : Sei-ichi SAITOH
     
    北海道大学Using satellite data set on ocean color and sea surface temperature before and after typhoon passing around Japan, we examined statistically abrupt change of primary productivity. The constructed relationship requires variables of typhoon maximum sustained wind, typhoon transit speed and bottom depth of the location below the typhoon track. Typhoon-forced primary production enhancements and typhoon contributions to summer-fall new production during El Nino years tended to be higher than those during La Nina years. We developed a numerical model of typhoon which can simulate a magnitude of mixing and upwelling in sub-surface layer and examined the upper-oceanic response to a moving typhoon and the mechanism of the response. We investigated the movement of the Kuroshio axis and the change of primary production on the northeast shelf of Taiwan associated with the passage of typhoons, using sea surface current data observed by ocean radar system.
  • Ministry of Education, Culture, Sports, Science and Technology:Grants-in-Aid for Scientific Research(基盤研究(B))
    Date (from‐to) : 2007 -2009 
    Author : Naomi HARADA
     
    独立行政法人海洋研究開発機構We have investigated temporal development of Emiliania huxleyi bloom on the continental shelf in the Bering Sea by a biomarker of E.huxleyi, C_<37> alkenones flux recorded in the sediments. As a result, the bloom had already been prominent since the middle of 1970's. We also found the E.huxleyi bloom would be promoted by active Aleutian low, positive anomaly of Pacific decadal oscillation and lowering of salinity.
  • Ministry of Education, Culture, Sports, Science and Technology:Grants-in-Aid for Scientific Research(基盤研究(B))
    Date (from‐to) : 2007 -2009 
    Author : Toru HIRAWAKE
     
    北海道大学In situ investigations in 2007 and 2008 and satellite remote sensing data revealed the following : 1. Smaller phytoplankton was dominant in 2007 compared with past years. 2. Remarkable decrease in distribution area of chum salmon is anticipated and the salmon will have to move toward north such as the Arctic Ocean where sea will be shrunk. 3. Significant change in species of demersal fishes with rapid decline of sea ice extent was not recognized.
  • Ministry of Education, Culture, Sports, Science and Technology:Grants-in-Aid for Scientific Research(基盤研究(A))
    Date (from‐to) : 2006 -2009 
    Author : Kenshi KUMA
     
    北海道大学Surface mixed layer of the basin region in the Bering Sea is under a typical iron-deficient and nutrient-rich condition with low primary production because of low atmospheric iron input. However, phytoplankton bloom (Breen Belt) is observed at the shelf break region of the Southeastern Bering Sea for a long period in summer. It is suggested that the Green Belt is maintained by the supply of nutrient-rich basin water and iron-rich shelf deep water to the surface water of the shelf break. The tidal mixing in the straits of the Kuril Islands is an important role on supplying nutrient and iron to the surface water of the northwestern North Pacific Ocean and maintaining the high primary production in the Oyashio region. On the contrary, the surface mixed layer in the Japan Sea is characterized by low nutrient and high iron concentrations, resulting from high atmospheric iron input to nutrient-depleted surface water of the Japan Sea close to the Asian continent.
  • Ministry of Education, Culture, Sports, Science and Technology:Grants-in-Aid for Scientific Research(基盤研究(A))
    Date (from‐to) : 2006 -2009 
    Author : Sei-ichi SAITOH
     
    北海道大学We carried out the development of monitoring methods on marine life and their environment and promoted various field observations in Shiretoko World Natural Heritage (SWNH) area. As a result, it is clear that there is difference in primary production system between northern coastal region and southern coastal region. We clarified 1) the effect of Pacific salmon (Genus Oncorhynchus) escapement on supply of marine-derived nutrients to the riparian ecosystems using the stable isotope analysis, and 2) to estimate escapement dynamics and spawning carrying capacity of the wild pink salmon (O.gorbusha) relating to the feeding behavioral pattern of brown bear (Ursus arctos) in SWNH area. Based on the adaptive marine ecosystem management, we proposed new method to evaluatean optimum fisheries operation for each fish species using both catch of fish and haul of fish in the Shiretoko coastal fisheries.
  • Ministry of Education, Culture, Sports, Science and Technology:Grants-in-Aid for Scientific Research(基盤研究(S))
    Date (from‐to) : 2004 -2008 
    Author : Michio KISHI
     
    北海道大学
  • Ministry of Education, Culture, Sports, Science and Technology:Grants-in-Aid for Scientific Research(基盤研究(B))
    Date (from‐to) : 2003 -2005 
    Author : Isao KUDO
     
    北海道大学Chemical substances and biochemical parameters were measured in the subarctic coastal region which receives fresh water and nutrients from the Tokachi River, one of the largest river in Japan. River discharge increased ten times after April due to a spring thaw and continued until June. In the coastal region, nutrients were depleted after a spring bloom which occurred in April. River plume area showed an elevated concentration of nutrients and iron originated from the Tokachi River. High concentration of chlorophyll a was observed only in the river plume because outside the plume nutrients were depleted. The mainstream of the Tokachi River and its tributaries showed different concentration of nutrients. This may be attributed to the different type of land use, i.e., farming, dairy farming, forest and city sewage plants. We also investigated the heterotrophic microbial process (microbial loop) which is related to the fate of organic carbon produced by phytoplankton. The abundance of heterotrophic bacteria was higher in the river plume than off shore region. Dissolved organic carbon was also higher in the plume. Riverine organic matter may accelerate the growth of heterotrophic bacteria in the plume. The mortality of bacteria was investigated by a dilution culture experiment. Virus infection was accounted for more than 80% of the mortality. The regenerated organic carbon may contribute to the further bacterial production.
  • Ministry of Education, Culture, Sports, Science and Technology:Grants-in-Aid for Scientific Research(基盤研究(B))
    Date (from‐to) : 2003 -2005 
    Author : Hiroshi HATTORI
     
    北海道東海大学In order to evaluate CO2 budget and ecosystem in the western subarctic Pacific, seasonal change s in phytoplankton abundance were observed by means of phytoplankton pigment analysis and cell-count to understand the physiological influences on the abundance in the upper layer off Kushiro, western Subarctic Pacific. Diatoms (larger cell size) were most abundant in the phytoplankton assemblage measured by pigments throughout the year although chrysophytes (small sized cell) were become dominant by cell-count particulary at offshore site. This reveals that water temperature was lower at offshore site than the coastal site because of low temperature preference of chrysophytes.Seasonal changes in the carbon budget in the surface layer will be estimated near future because cell count is not completed yet on our whole samples.
  • Ministry of Education, Culture, Sports, Science and Technology:Grants-in-Aid for Scientific Research(基盤研究(B))
    Date (from‐to) : 2003 -2005 
    Author : Yasunori SAKURAI
     
    北海道大学Recruitment success in squids depends largely on environmental conditions at the spawning and nursery grounds. The autumn and winter spawning groups of Japanese common squid, Todarodes pacificus have the largest biomass and the annual catch of winter groups have fluctuated widely. T.pacificus produces gelatinous, nearly neutrally buoyant egg masses that contain many small eggs. The egg masses are thought to occur within or above the pycnocline at temperatures suitable for egg development (e.g., 15-23℃ in T.pacificus) and under conditions of reduced predation. After hatching, the paralarvae presumably ascend to the surface layer and are advected into convergent frontal zones We observed something resembling a T.pacificus egg mass within the pycnocline at 70-120 m depth (temperature range : 18-21℃) in the Tsushima Current using an ROV. We also estimated from laboratory studies that hatchlings ascend to the surface at temperatures of 18-23℃. We used this new reproductive hypothesis to estimate winter spawning areas of T.pacificus. Results of a previous study suggested that annual catches of T.pacificus increased during periods of weak winds and warm air temperature, suggesting that the strength of winter winds may affect recruitment. The spawning areas of winter spawning group during warm regime after 1990's were estimated to be along the continental edge off the Kyushu Island and the Nansei Islands. Inner flow of Kuroshio will transport paralarvae in surface layer from the spawning areas to the nursery areas of northeastward along the continental edge. However, the spawning areas during cool regime during 1980's were reduced along the continental edge. We can present a scenario for how stock size in T.pacificus might fluctuate due to environmental factors such as sea surface temperatures and suggest how to forecast the stock fluctuation related to climatic regime shifts and global warming.
  • Ministry of Education, Culture, Sports, Science and Technology:Grants-in-Aid for Scientific Research(基盤研究(B))
    Date (from‐to) : 2002 -2004 
    Author : Sei-ichi SAITOH
     
    北海道大学Objectives of this study are (1) to clarify a response of several populations from lower to higher trophic levels to physical and biological environment change, especially we focused on the key spices, walleye pollock in the Bering Sea, and salmon, pomfret and flying squid in the Gulf of Alaska, and (2) to examine difference of primary production systems in both Western Sub-Arctic gyre and Alaskan Gyre in consideration of iron limitation in HNLC regions using in-situ and satellite observations. Moreover, we tried to develop new observation and sampling methods for surveying fish populations and spatial distribution of fish using ROV and underwater remote sensing.In this study period, we carried out three in-situ observation cruises by T/S Oshoro-Maru in summer 2002, 2003 and 2004. In 2003 and 2004, we had two transects survey along 165 East long. and 165 West long. in order to compare east-west gyre systems. In summer 2003, we had a chance to hold the mini-symposium of "Marine Ecological Studies in the Bering Sea and the North Pacific-Commemorative symposium for UH-HU academic exchange agreement and to mark the 2003 cruise of the T/S Oshoro Maru" in University of Hawaii, Honolulu, U.S.A., then presented our preliminary results and had a fruitful discussions.
  • Ministry of Education, Culture, Sports, Science and Technology:Grants-in-Aid for Scientific Research(基盤研究(A))
    Date (from‐to) : 2001 -2003 
    Author : Sei-ichi SAITOH
     
    北海道大学It is very important that we develop multi-dimensional sensing in combined with satellite remote sensing, underwater remote sensing and direct survey to predict when, where and how much are marine living resources available. Objectives of this study are to develop methodology of multi-dimensional sensing of marine living resources and their environment and to monitor three-dimensional distributions of Japanese common squid and three dimensional environment using acoustic with towed body transducer and real-time towing CTD system with satellite images. Major results are as follows :(1)Observation depth of real-time towing CTD system is from 10 meter to 80 meter in the condition of the length of wire of 300 meter and ship running speed of 10 knot.(2)Three-dimensional observation in the southeastern Bering Sea was successful to gather environmental structure and biomass of fishes using real-time towing CTD and acoustic system EK500. Visualization those three-dimensional distribution was established using AVS software.(3)In the First Oyashio intrusion region off Cape Erimo, three-dimensional fine structure was observed using real-time towing CTD system and acoustic system.
  • Ministry of Education, Culture, Sports, Science and Technology:Grants-in-Aid for Scientific Research(基盤研究(B))
    Date (from‐to) : 2000 -2002 
    Author : Yasunori SAKURAI
     
    北海道大学In short-lived squids, recruitment success most likely depends on the physical and biological environments at the spawning and nursery grounds. No egg masses have been observed in the natural habitat. During 2000-2002, MOCNESS and an ROV were used to examine the distribution of egg masses and paralarvae of Todarodes pacificus in the Sea of Japan. Gelatinous egg masses were observed at two stations in the Tsushima Current along the continental shelf off the Oki Islands in November, 2000. They occurred within the pycnocline (75 and 95 m depth, respectively), where temperatures were about 18℃, which was suitable for embryonic development. Upon hatching, paralarvae may rise to the surface layer, where they would be carried into the convergent frontal zone in the Tsushima Current.Annual catches of T. pacificus, have markedly increased since the late 1980s, and recent catches have equaled those of the 1960s. The winter spawning area of T. pacificus in the East China Sea shrank when adult stocks decreased during a cool regime that occurred before 1988, and that its fall and winter spawning areas extended and overlapped in the Sea of Japan and East China Sea when adult stocks increased during a warm regime after 1989. Successful hatching from egg masses was to be higher when the mixed layer depth (MLD)is shallower than the bottom depth. We examined the relationship between annual catch of the winter-spawning stock, and wind speed and air temperature in the East China Sea in February during 1980-2000 to determine how a series of calm and warm winters might promote a stock increase related to changes in the MLD. Annual catches markedly increased during a decade of weak wind speed and warm air temperature from the mid-1980s to mid-1990s, suggesting that the strength of winter wind stress affects the winter-spawning stock fluctuations in T. pacificus.
  • Ministry of Education, Culture, Sports, Science and Technology:Grants-in-Aid for Scientific Research(特定領域研究(B), 特定領域研究)
    Date (from‐to) : 1999 -2002 
    Author : Ken FURUYA
     
    東京大学Bio-optical monitoring of primary production using in situ sensors and ocean color remote sensing was examined for Northeast Asian marginal seas of the Pacific Ocean. In situ monitoring was conducted by the continuous measurement of natural fluorescence with which improved algorithm resulted in a satisfactory accordance with carbon uptake. Regional algorithms for estimating primary production from remotely sensed information were examined with published algorithms using bio-optical parameters obtained during cruised conducted between 1999 and 2000 in Japan Sea and the East China Sea. Pbopt and chlorophyll a were found to be most critical parameters in both areas. While Kameda-Ishizaka algorithm yielded best performance in the validation, estimates varied in the factor of 2, on average, posing requirement of further improvement. Time series observations of chlorophyll a and primary production from 1996 to 2002 using data obtained by both OCTS and Sea WiFS revealed year-to-year variations in both timing and magnitude of spring bloom in Japan Sea. In contrast to Japan Sea, case 2 water issue was distinct throughout the year in the East China Sea.
  • Ministry of Education, Culture, Sports, Science and Technology:Grants-in-Aid for Scientific Research(地域連携推進研究費)
    Date (from‐to) : 2000 -2001 
    Author : Takeshi KISHINAMI
     
    北海道大学・A Web-XML based distributed database system was developed for archiving and distributing the eco-resource data observed in Hokkaido university by integrating RDBMS, Web, XML and Java technology. (Satoshi Kanai, Fumiki Tanaka, Seiichi Saitoh, Kohji Iida, Hiroshi Tani and Takeshi Kishinami)・"Hokudai Himawari Server" was developed so that GMS data are distributed via the Intenet on real time with a form extracted from original disk image, which had not been available in Japan. (Tani, Yazawa and Kanai)・To enhance ability of distribution and re-usability for the eco-resource data, UML/XML/Java 3-layer development method for eco-resource simulation based on ISO 19000 series was proposed and it was applied to ocean ecosystem simulation (Fumiki Tanaka, Seiichi Saitoh and Takeshi Kishinami)・A data compression method was developed for time series of satellite remote sensing images based on 3D wavelet transform. And a digital watermarking method was developed to protect copyright of the vector-typed geographic information, and to prevent it from tampering. (Satoshi Kanai)・We examined effects of the past three-decadal and seasonal changes of marine environments, including sea surface temperature, currents, warm-, cold-eddies and sea surface height to stock fluctuations of Ommastrephid squid, Todarodes pacificus, Loligo squid, Loligo bleekeri, and walleye pollock, Theragra chalcogramma in waters around Hokkaido. (Kohei Yamauchi and Yasunori Sakurai)・A database on abundance distribution of walleye pollock off western Hokkaido, based on the acoustic fish resource survey was constructed. Methods to estimate the horizontal distribution and the vertical distribution of relative abundance of every 50 meters depths were developed. Then the abundance of walleye pollock in spawning ground in the West Coast of Hokkaido was predicted and the three dimensional distribution of fish resources were analyzed. (Kohji Iida)・Fisheries Oceanography GIS developed by satellite date sets (SST, Chlorophyll-a , night light images etc. ) and fisheries statistics, and its application to near real time on-line system for coastal zone monitoring. (Seiichi Saitoh)・The seasonal changes of water quality and depth on small ponds in Ishikari peatlands were studied. The continued use of land in the vicinity of ponds as paddy fields would greatly contribute to the preservation of the ponds. (Masao Yazawa)・A method analyzing relationship between satellite data and meteorological factors of agricultural field was developed in order to estimate crop yield. (Hiroshi Tani)・Plane images of the soybeans and sugar beets rows were taken by VTR camera. The developed method was utilized to create maps of dry mass, height and growth rate from recorded images. (Shun-ichi Hata)・We developed a crop growth model to evaluate the effects of sub-optimal temperatures and availability. Thermal image analysis was found to serve as a tool for detecting the difference in crop response to soil water deficit between crop genotypes. (Toshihiro Hasegawa)・Distribution of healthcare resourses in Hokkaido are surveyed using GIS and proper allocation of healthcare delivery is analysed. Also the quality of digital motion image transmission for telemedicine is assessed. (Tunetoro Sakurai)・Concepts of data base system and models for integrated water resources management were developed. The system includes models for rain water run off process ; river system ; groundwater system ; fate and transport of contaminants ; structure of water demand ; human risk asscssment. (Naoyuki Funamizu)
  • Ministry of Education, Culture, Sports, Science and Technology:Grants-in-Aid for Scientific Research(国際学術研究, 基盤研究(B))
    Date (from‐to) : 1998 -2000 
    Author : Tsutom IKEDA
     
    北海道大学From 1998 to 2000, in summer, we carried out field works in the Gulf of Alaska and Bering Sea using T/S Oshoro-Maru with collaboration of U.S.and Canadian Scientists for studying on ecosystems dynamics in the northeastern Pacific. We planed this joint study with University of Alaska and University of Washington which are one of sister faculties or universities. Outline of the research results is as follows :(1) We studied the temporal and spatial variability of coccolithophore blooms in eastern Bering Sea shelf using ship and satellite observations.(2) We carried out plankton sampling using various plankton net and studied quantitatively plankton community structure.(3) Using non-selection gill net, we sampled higher trophic levels organisms to study community structure and food relationship. As a result, there was a lot of squid from salmon stomach contents and the importance of squid are emphasized.(4) We carried out primary production measurements in eastern Bering Sea using 13C method. As a result, there was high productivity in the shelf break region as called "Green Belt" in compared with shelf region.(5) We carried out cephalopod paralavae sampling in the Gulf of Alaska and eastern Bering Sea to study vertical distribution and latitudinal body-size gradients.(6) We carried out micro-nekton sampling using mid-layer trawling in the Gulf of Alaska.In 1998 and 2000, we had two one-day workshops at each port of T/S Oshoro-Maru. Workshop "Ecosystem Dynamics in the Northeastern Pacific and the Bering Sea" was held in Seattle 1998 and Workshop "Marine Ecological studies in the Bering Sea and eastern North Pacific" was held in Victoria 2000. U.S., Canadian and Japanese scientists could exchange the information of each scientific program.
  • Ministry of Education, Culture, Sports, Science and Technology:Grants-in-Aid for Scientific Research(基盤研究(B))
    Date (from‐to) : 1998 -2000 
    Author : Sei-ichi SAITOH
     
    北海道大学(1) Processing of DMSP/OLS images and data base generationWe gathered DMSP/OLS images covering Japan Sea and off Sanriku from 1994 to 1999 and generated Data base of fishing fleets distribution.(2) Processing of satellite sea surface temperature and ocean color images and data base generationWe gathered NOAA/AVHRR, ADEOS/OCTS, Orbview-2/SeaWiFS images covering Japan Sea and off Sanriku from 1994 to 1999 and generated Data base of SST and chlorophyll a.(3) Investigation of meso-scale eddies using altimeter sea surface height data.We investigated the distribution of meso-scale eddies, Kuroshio warm core rings (KWCR) and Tsugaru warm current gyres (TWCG), using TOPEX/ERS-2 sea surface height anomaly data.(4) Statistical analysis of squid fishing fleets distribution(5) Analysis of the relationship between fishing fleets distribution and SST distributionWe analyzed the position of squid fishing ground and the distanc e from SST fronts.(6) Observation of fishing fleets distribution from Mt. Hakodate using digital cameraWe developed a methodology to analyze from oblique photograph to vertical photograph and could count the number of fishing fleets in a pixel of OLS images.(7) Analysis of migration routes of Pacific sauryThe coalescence of KWCR-93A and TWCG in 1995 and 1998 cut off the intrusion of the first branch of Oyashio as one of the migration routes of Pacific saury. Fishing grounds moved to offshore and it indicated the coalescence was important phenomena changing the migration routes.
  • Ministry of Education, Culture, Sports, Science and Technology:Grants-in-Aid for Scientific Research(基盤研究(B))
    Date (from‐to) : 1997 -1999 
    Author : Yasunori SAKURAI
     
    北海道大学Reproductive strategy related to stock fluctuation on the ommastrephid squid Todarodes pacificus are examined by field survey and captive experiments. Immature squid were collected and maintained in a raceway tank where they matured, mated, and spawned. Gelatinous egg masses were spherical and nearly buoyant. The largest egg mass measured 80 cm in diameter and contained approximately 200,000 eggs. The egg-mass surface layer effectively prevented crustaceans, protozoans, and bacteria from infesting the masses. Paralarvae hatched after 4-6 days at 18-19℃ and actively swam at once, with many individuals swimming at the surface. Egg masses disintegrated soon after hatching. Survival of eggs and paralarvae were examined at temperatures ranged from 3.5-29℃ to determine the optimum temperature range for development and survival. Highest embryonic survival rates occurred between 15 and 23℃. It is sugggested that T. pacificus spawns in waters warmer than 15℃, and egg masses maintain their structure for about 4-9.5 days before disintegrating at temperatures between 15 and 23℃.The inferred spawning sites of T. pacificus around Japan are assumed that egg masses and hatchlings occur at temperatures between 15 and 23℃, and above the continental shelf and slope, because captive females regularly sit on the tank bottom just before spawning. Annual catches of Todarodes pacificus in Japan have gradually increased since the late 1980s. Paralarval abundances have also been higher since the late 1980s than during the late 1970s and mid-1980s. We propose a possible scenario for the recent stock increase based on changing environmental conditions. First, we examined trends in the annual variations of stock and larval catches, and infer potential spawninig areas, assuming that egg masses and hatchlings occur at temperatures between 15 and 23℃, and over the continental shelf. We then infer changes in the spawning areas during 1984-95 based on GIS data. We conclude that since the late 1980s the fall and winter spawning areas have overlapped in the Tsushima Strait and near the Goto Islands, and that winter spawning sites have expanded over the continental shelf and slope in the East China Sea.
  • Ministry of Education, Culture, Sports, Science and Technology:Grants-in-Aid for Scientific Research(基盤研究(B))
    Date (from‐to) : 1996 -1997 
    Author : Hideo MIYAKE
     
    北海道大学Hydrographic conditions and low trophic productivities were investigated with using mooring systems, satellite image analysis and ship observations during the spring bloom in 1997. Results are summarized as follows ;1) Chlorophyll-a concentrations and fluxes of settling organic particles in the sediment trap were poor in middle March. It is concluded that the phytoplankton bloom was weak in spring of 1997. Coastal Oyashio Water flowed weakly into the bay. This is a reason why the spring bloom was weak in 1997.2) Ocean color satellite and ship observations showed high chlorophyll-a areas off Muroran to the center of the bay mouth. Waters of the high chlorophyll-a areas moved into the bay. This suggests that the wind-driven currents are important for the distributions and movements of the plankton.3) Resuspention perticles from the bottom sediments were trapped under the southeasterly winds. This is explained as follows ; high wind waves and resuspentions of the shallow sediments inside the bay cause by the southeasterly winds which have a long fetch. These particles move with the southeastward flows drived from the vortex pair and fall into the trap at the center of the bay.4) Copepod nauplii are main organisms in early life stage of walleye pollock. After the inflow of the coastal Oyashio Water, large copepod nauplii become to be abundant near the bay. When spawning areas shifted the northeast ward, Oyashio Water was favor food conditions for the larvae, and it transported efficiently eggs and larvae into the bay. This is one of reasons for the long term variabilities of the year class strength of walleye pollock.
  • Ministry of Education, Culture, Sports, Science and Technology:Grants-in-Aid for Scientific Research(国際学術研究)
    Date (from‐to) : 1995 -1997 
    Author : Kiyotaka OHTANI
     
    北海道大学During Bering Sea surveys by the T/S Oshoro-Maru of Hokkaido University in the summers of 1995,1996 and 1997, we conducted a joint study of the bioclimatology in the Bering Ses with sientists from the University of Alaska, Fairbanks. In this study, we examined the relationship between the physical environment, production structure and recruitment of keystone species, including walleye pollock Theragra chalcogramma, related to recent climatic changes in th Bering Sea ecosystem. The results will be published in teh Memories of the Faculty of Fisheries.Hokkaido University, in the summer of 1998. A summary of our joint study is as follows :1. We studied coastal upwelling in the St.Lawrence Island Polynya in the summers of 1994 and 1995 by satellite and ship observations.2, We clarified interannual variation and vertical distribution of appendicularians in the St.Lawrence Island Shelf in summer.3. We examined biophysical processes relevant to recruitment dynamics of walleye pollock in the eastern Bering Sea during the summers of 1995,1996 and 1997. We will present a conceptual model of factors influencing pollock recruitment in this area.4. We clarified the effect of temperature and salinity on development and survival of eggs and larvae of Arctic cod, Boreogadus saida as an indicator species related to climatic change in the Berin Sea.5. We studied the bottom fish composition and food habits in the southern water off the St.Lawrence Island in the Bering Sea.
  • Ministry of Education, Culture, Sports, Science and Technology:Grants-in-Aid for Scientific Research(総合研究(A), 基盤研究(A))
    Date (from‐to) : 1995 -1996 
    Author : Sei-ichi SAITOH
     
    北海道大学In this sutdy, we focused on the processes of material transportation from coastal region to offshore region through surface layr. We selected Tokyo, Ise, and Osaka Bays as typical coastal regions which are connected to the Kuroshio water and are also facing to industrial area and high density of population region considered as most eutrophicated coastal zone. Material transportation from these bays to offshore through surface layr might be responded to variation of main Kuroshio Path as oceanic forcing from offshore to coast. The objective of this study is to clarify an mechanisms on material transportation and to estimate quantitatively the volume of material transportation. We attempted interdisciplinary approach using combination satellite remote sensing, numerical modeling, and in-situ synoptic observation. This approach with comparison of three bays should be defined as an comparative coastal oceanography. Summary of our results is as follows : (1) There is a difference outflow process of suspended matter between Ise Bay and other Bays in winter. (2) Outflow patterns of suspended matter from Tokyo Bay is defined two patterns by using high resolution satellite remote sensing. (3) We examined a ratio of outflow of suspended matter from surface layr and bottom layr. (4) We developed coastal diagnostic numerical model for each bays. (5) The characteristics of the variation in the Kuroshio path south of Japan is studied by use of the observational distance of the main Kuroshio path from Japanese Coast over period of 1995-1994. (6) Budgets of fresh water, salt, DIP and DIN in Tokyo, Ise, Osaka Bays are studied and we understand the characteristics of material cycling of each bay.
  • Application of Satellite Remote Sensing to study on the Variability of Migration Route of Epi-pelagic Fishes.
  • Study on Spatial and Temporal Variabilities of Primary Production in the North Pacific Ocean Using Satllite Remote Sensing
  • Application of GIS technology to the Fisheries Resource Management and Fisheries Operation


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