1993 Hokkaido-nansei-oki earthquake occurred only 10 years after 1983 Nihonkai-chubu earthquake, and both earthquakes induced serious tsunami disaster. After these events, a new idea has been born that there exists a plate boundary in the eastern edge of the Japan sea, and a possibility is pointed out that earthquakes with the same order of magnitude may occur in some areas on the plate boundary where no great earthquake has occurred for a long time. Thus a need arises that in the construction of coastal dikes tsunamis should be taken into consideration as a design force in addition to sea waves which have currently been taken into account. Therefore, a high resolution tsunami simulation model has been required to estimate neccessary heights of coastal dikes against possible future earthquake tsunamis. The model con sists of fine grids of 0.2km spacing along the eastern edge of the Japan sea and coarser grid systems with 0.6km to 3.6km spacing covering the whole Japan sea. In order to evaluate model reality, 1983 Nihonkai-chubu earthquake and 1993 Hokkaido-nansei-oki earthquake tsunamis were reproduced using the model. Very good agreements were observed with respect to coastal distribution of inundation heights, arrival time of the first tsunami wave and time histories of water surface and current velocity.

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Irradiation of UV (UVA + UVB) on the embryos of the planktonic copepod Calanus sinicus caused damages to their development. Hatching rate was reduced, and the hatched larvae were deformed by the UV-B irradiation at naturally occurring intensities. However, the UV-induced damages were reduced by the simultaneous irradiation of the visible light from a fluorescent lamp. The photoreactivation may play an imporant role in reducing the mortality of this species in marine environment.

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Big catfish Silurusbiwaensisis one of the endimic species in the Lake Biwa. However, there is no enough biological information to conserve the big catfish since it is unpalatable so that it is not an object of commercial fisheries in the Lake Biwa. The migration behaviour of the catfish was examined by means of the ultrasonic biotelemetry system to clarify the migration path. Two tracking studies were carried out. One was long period tracking thoroughout six months from May to December 1995, and another was a 24-hour continuous study. Ultrasonic transmitters were attached to all catfish samples before they were released. In the long period studies, six individuals were released at releasing points before spawning season and five individuals were releasedto the spawninggroundin the spawning season. Onlyone fish was foundin the spawning ground and the others were found around the released points in the former study. All the five individuals were found in their habitat in the latter study. In addition, in the 24-hour study, an individual was released in the midnight. It was settled in the shallow water near the spawning ground in the daytime. These results suggested that the big catfish may migrate from releasing points to the spawning ground and it is the nocturnal habit. The ultrasonic biotelemetry is a pow erful technique to investigate fish migration.

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Importance of forecasting of fisheries condition utiling oceanographic features has been now well established and this is going to play a very important role in sustenable management of fisheries resources in feature. In this study, it was attempted to forecast the oceanographic feature pattern from the oceanographic information using neural network. As the factors of input unit layer, hydrographicprincipal factors (warm-core ring off Sanriku, warm-core ring off Kushiro.nearshore intrusion of Kuroshio, offshore intrusion of Kuroshio, first branch of Oyashio, second branch of Oyashio) were utilized in this study off Tohoku. Hidden layerwas fixedfor only one layer.and it had fourhidden nervecells.The abovefactors from 1981 to 1993ware made use of in the system of neural network for forecasting oceanographic features in 1994 and 1995. And then.this system was valued by comparison of estimated pattern of oceanographic features with real one. It was made certain that the estimated pattern of oceanographic features agreeable with the real one within 60 nautical miles, and this neural network system would be useful for application of forecast of oceanographic feature pattern.

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Routine analytical method of organic carbon and nitrogen in marine sediments were de scribed, and results of the method were compared with those of acid wash-out method. Samples were treated with UCl to remove carbonate within ceramic sample boats, by drop ping UCl using microsyringe, and organic carbon and nitrogen were determined with Yanaco MT-5 CHN analyser. The method were applied to sand of tidal flat, silt of estuary, sediment trap particles and coralline samples. Precision (CV%) were 4-8% for organic carbon and 8-14% for nitrogen. 10 -30% of organic carbon and nitrogen were lost by wash-out acid treatment.

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Red Tides, caused by an explosive increase in phytoplankton, frequently cause great damage to inshore fisheries. As occurrences of Red Tides have increased, the Japan Fisheries Agency has funded many research projects, with the aim of protecting fishery grounds from damage, an ex tensive range of data have been continually collected to elucidate the trigger to the explosive plankton bloom. With advances in research and data accumulation, it became necessary to develop a database system that allows researchers to analyze geographical sea conditions and to produce graphical views based on a huge data set. Thus, a database system using public communication lines was designed. Using the prototype of this system, marine researchers are able to quickly get collate informa tion about Red Tide blooms and a range of related data from all coastal areas of Japan.

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The usefulness and limitations of models of natural systems have recently been summarised by Oreskes et al. (1994) who have argued that the primary value of models is heuristic, providing guidance for further study. A number of simple (mainly one-dimensional) models of the marine ecosystem are reviewed in this context. It is shown that many aspects of the balance of CO, and of the phytoplankton seasonal succession that were observed along 20°W during the North Atlan tic Bloom Experiment in 1989 can be represented by such models and these make additional predictions about how the system operates. Examination of data from the Continuous Plankton Recorder Survey indicates that these models may be applicable to the conditions during most years but may not be suitable for the western North Atlantic. In a second example, the problem of modelling the observed climatic connection between the latitude of the Gulf Stream and zooplankton abundances around the UK is considered. This climatic signal appears to become mani fest in the zooplankton via the annual cycle of thermal stratification. It is shown that this process can be replicated by forcing existing models of the shelf-seas plankton with three decades of meteorological observations. These calculations reveal the aspects of year-to-year differences in weather to which the planktonic ecosystem is sensitive.

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