The plaice Pamlichthys olivaceus is important fishery species in Japan. As the fishing amout of them is declining in a few decades propagation ofthem is doing by means of creation of nursery grounds in the coastal sea. Knowleges of biological character of objective fish is essential for the propagation. The author has continued the basic research to define ecology and physiology of the plaice larvae and juveniles to contribute to effective creation of nursery grounds of them. First of all, the suitable environmental condition and specific gravity (∂t) of eggs and larvae, and swimming speed of larvae of them were examined. Hatch ratio of eggs was the highest on 15℃ in water temperature and on about 42‰ in salinity. Specific gravity of eggs varied between 21 and 27 according to development and of larvae did between 23 and 58 according to growth. Short period swimming speed of larvae increased to about 6cm/s from 1cm/s according to growth. Sustainable swimming speed decreased almost according to time lapse from beginning of measurement. Reaction of larvae to the change of illuminance and to the diffrence of salinity in the tank were examined next by expermental ways. Larvae moved vertically in the transparent plastic pipe according to the change of illuminance and tended to distribute more frequently in the low salinity layer of the density stratiffication tank. Finally, the prey demand of juveniles was examined by both eclogical way and experimental one. Juveniles below 8cm in total length tended to eat only mysids and ones over 10cm do to eat shrimps and fish. Some ideas for creation of the nursery grounds of the plaice were suggested being based on the result of this reserch in addition.

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To create a new artificial shallow area in a hypoxic bay, we propose methods to determine the depth for the area and how to evaluate its effectiveness. The study was conducted in Mikawa Bay, Japan, which is a semi-enclosed sea and is regularly nutrient enriched. As a result, in summer, serious hypoxia is observed in the bottom layer, which becomes progressively lethal to the macrobenthos. Therefore the aim of developing a new shallow area should be to avoid hypoxia. The circumstances on which we developed the new method are described. Future technical subjects for the environmental restoration are also described.

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The covefage of H. ovalis Hooker f. in a mixed Zostera meadow, Z. marina L. and Z. caespitosa Miki was investigated to examine the effect of interspecific competition on its distribution. The coverage of H. ovalis in the vicinity of Z. caespitosa was lower than that of Z. marina. This result suggested that the growth of H. ovalis was inhibited in Z. caespitosa meadow. The canopy height of Z. caespitosa was higher than that of Z. marina, which caused to light reduction in the vicinity of Z. caespitosa. Z. marina canopies decreased due to the feeding behavior of fish. Intercepting light by Z. caespitosa canopies migght be a factor responsible for the poor coverage of H. ovalis in the Z. caespitosa meadow.

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The sweet fish (alevin ayu plecoglossus atlivelis) hatch out in the shoals of river and they drift down the river into coastal zone immediately This study is carried out survey of salinity, water temperature and dissalved oxygen in the tidal compartment of Niyodo River to understand the environmental characteristics of flow and water quality in the compartment for the drifting sweet fish. Niyodo River is ohginated from Mt. Ishizuchi (1,982m) that is the highest mountain in the west of Japan and running through the Kochi-Plain and into the Tosa Bay. Niyodo River has a length of 124km with 1,560km² of the river basin. The maximum discharge is 5480m³/s, the minimum is 9m³/s and the annual mean flow is 118m³/s. In the river mouth, the width is about 1km and the groin had been established at the left side. But the usual flow is 60m width because sand spit has been developed. It is shallow in river mouth. Riverbed is so irregular where there is over 10m depth in a part. The tidal range is about 2m at the flood tide and about 0.6m at the neap tide. In the river mouth, the water level changes with the tide.

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Seasonal changes of Zostera marina L and physical environment factors (underwater irradiance, Sandy bottom quality etc.) were examined off Miya in the Mikawa Bay, Aichi Prefecture, from 2000 to 2001 Japan. Z. marina forming seagrass beds grew densely from February to June, and declined from July to October. While a large number of juveniles geiminated from their seed started to appear toward the middle of October, and Z. marina grew densely again in the following spring. Most of the Z. marina off Miya was annual. Vertical distribution range of Z. marina beds were from D.L. +0.5m to -1.6m depth. From the site irradiance conditions in the seagrass bed, the deepest bottom of Z. marina possible growth was estimated to be D.L.-1.8m. The high temperature in the summer was the important cause that the Z. marina beds were decreased. Surface layer of the bottom was reductive conditions enough to germinate. These observations suggest that Z. marina of annual plant requires calm environmental conditions as one of the required suitable conditions for successful seagrass bed formation.

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The management of fishing boats in Japan is mostly under the economical crisis because of the shortage of catch and cheep fish prices etc. Fishing Boat and System Engineering Association of Japan has taken several initiatives since last few years to improve the situation through Japan Fisheries Associalon. The high-level technical system engineering development of fishing boats in North European countries has contributed remarkatly the fishing boat industry. They concern, for instances, the technical operation system of mid-water trawler, the fish container system using refrigerated sea water, the combination system utilizing long range fish finding sonar and auto-trawling system, etc. The fishing boat operation in Japan is too expensive in terms of labor cost and it should be changed into more economical one through mechanization. For this purpose, a lot of technical study and developing activities should be promoted inmediately by the combination activities of the fishermen and technical engineers belong to universities, research institutes, and commercial companies. At the same time, each fishing boat manager should care about over-fishing and sustainability of fish resources. Thus he should catch fishes more reasonably from the viewpoint of economical fishing operation. The regulation for the fishing boats should also be changed to let the fishing boats can operate more safe and economically.

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As practical computational fluid dynamical method fbr designing ship hull forms, Rankine source panel method is exanined for improving fishing vessels. The method is applied for designing a bulge form to reduce. the wave making resistance. The fluid dynanics mechanism producing a bulge effect is expressed and an optimized bulge form is derived on the basis of the calculated wave, pressure and resistance. Next, calculated results are shown for difference of the propulsive perfomance between a Japanese middle trawler and a similar North European one. The inferiority of hull form of Japapese fishing vessel is pointed out from viewpoint of comparison. Thirdly, this method is used for developing a super wide beam vessel and the advanced fishing hull form is proposed. The possibility to pracdcal application is discussed.

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Fishing vessels are usually equipped with a large rudder area and initial trim, which gives them better manoeuvrability. This large rudder area ratio, however, causes the capsizing accident when large anount of fishes is loaded on board. It is reported that the cause of the accident of the Japanese trawler 'Ryuhonaru V' is an example of this scenario. As for the principal dimension of modern fishing vessel, length beam ratio becomes small particularly in North Europe. For such new type of fishing vessel, a suitable steering device must be designed, because the course-keeping ability of wide beam ship generally becomes worth. In this paper, the author reviews the suitable steering device and its operation for the fishing vessel. Further more, he shows the use of simple roll stabilization technique using this steehng device, with good potendal of application in future.

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Seasickness has always been a serious issue for people prone to motion sickness. Obviously if passenger comfort could be improved, they would easily get on board much alike as getting in a car. The design of the ride control system for a fishing vessel presents special problems due to the need to optimize the arrangement of actuator. In addition, the effect of this system sometimes gives a different reputation among the shipbuilder, ship-owner and fishermen. The main reason is that they do not have a common long measure related to seasickness. In this paper, a new evaluation method of the hde control system for a fishing vessel has been proposed from the viewpoint of human engineering. The method evaluates the amplitude of accelerations, their frequencies and the influence of exposure duration. The point about the development of this method takes into account the influence of exposure duration during the boarding time. In the evaluation method, the effect of ride control system is quantitatively discussed among the shipbuilder, ship-owner and fishermen.

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Nowadays, the fishing industry has been under the grave states because of the decrease in resources and nunning problem. Moreover, the aging problem of crewmembers is proceeding rapidly. It is predicted taht the lack of successor will be faced and the skill relating to the fishing will not succeed to promising youths in the near future. To maintain sustainable fishing production, it is essential to improve such serious conditions and we have to make the fishing an occupation with a bright prospect. In this paper, I focused on the acceleration generated on the ship, which directly affects health and safety of crewmembers. Based on the reslts of BEAMER 2000 profect in the Netherlands, I suggest a view of future fishing vessel with safety and proper environment in relation to the working and the accommodation.

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