With a view to develop a solar battery system for fishing boats, a long-tem experiment was conducted to evaluate the photo voltaic generating system with constant voltage control of the solar battery. The results showed that the output voltage of solar battery was always maintained constant. The ratio of solar radiation to electric power, i. e. efficiency was 11% on the average. However, the efficiency (Ef) during the experiment was a function of the mean temperature (Tm). An empirical equation was developed as follows. Ef = -0.0747　+　0.0162×Tm　-　3.24×10^-4　× Tm² These results lead to the conclusion that this system should be improved such that the efficiency is kept constant aｌｌ the time for a greater range of temperature.

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Transport processes of pelagic eggs and larvae of brown sole (Pleuronectes herzenseini) from the spawning ground near the Sado Strait in Sea of Japan were investigated using an Euler-Lagrangian numerical model. Since coastal currents under the wind influence and the interaction of vertical movement of eggs and larvae with the currents could have significant effects on the transport, numerical simulations using three types of wind conditions (north wind, west wind and west-south-west wind: the wind speed is 4m/s in each case.), two kinds of inflow condition (fast and slow), and two pattems of vertical movement (passive and active) were made to explore their influence on the transport process. The retention rate, which indicates the percentage of eggs and larvae retained in shelf areas shallower than 100m, ws calculated for each case. The retention rates under the westerly winds are appreciably high compared to those under the north wind. However, when the westerly wind speed is over 5m/s, the rates for the cases of passive movement rapidly decrease. On the other hand, the rates for the cases of active one are maintained as 100% even under the strong Winds, because the eggs and larvae tend to be transported along the shore line. This suggests that westerly winds, which are generally dominant during the spawning period of brown sole, could enhance the larval retention in the coastal water in combination with the vertical migration of larvae.

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It has been known that the dynamic response of rolling motions of small fishing vessels in the sea exhibits nonlinearities, because of some characteristics caused by the shapes of their bodies. This paper considers a methodology for applying a Neural Network model to the structure of the above response, and the effectiveness of forecasting the above rolling motions using this model. Comparisons of perfomances of forecasting between the method using a Neural Network model and a predictor of an autoregressive (AR) model suggested that it might be more effective to use a Neural Network model than to use an AR model. It means that the method for forecasting using a Neural Network model might be more reasonable to forecast the above roll motions than a linear forecasting method.

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The pedometer readings of the 18 crew members having different jobs on board a 2,000 G.T. fishery training vessel were recorded twice a day over 53 effective days during the New Zealand-Hawaii Cruise in 1994-95. Using these records, the influential factors in the walking activity of the respective members were sought by estimating the multiple linear regression equations for the number of days sailed, the AM-PM dummy variable (category 1), the area dummy ones (category 2) and the variables relating to the surface conditions (category 3). The following results were obtained : (1) The fom of the equation expressing the activity of the respective members differed according to the members with respect to the actually adopted variables and the sign of their partial regression coefficient, (2) the walking activity primarily depended on the variables in categories 1 and 2, and secondarily on those of category 3, and (3) interviews with the members concemed indicated that the obtained results including the diversity in the estimated equation had a close relation to the details of the duty work.

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The volcanic activities of Unzen. Fugen-dake had commenced in November 1990. The frequent large scale avalanche of earth and rocks in the volcanic activities had carried in a lot of fallen trees to Shimabara Bay. After these fallen trees had come in Shimabara Bay, Some of them were burried under volcanic ash near the mouth of Mizunasi river or drifted with the current, and brought a heavy damage to fishermen and sea-going ships. Research of the drift actual condition of floatage in Ariake Sea is'nt done, although current reseach have been rather extensively studied. Hence, the authors wish to present in this report the results of basic experiments. We made a mimic drift wood, and equipped it with GPS receiver. And we researched the actual condition of drift situation through the pIot of the mimic driftwood tracks, further apalyzed the wind effect which swayed the driftwood. We found that the driftwood pass through the Hayasaki strait during one or two ebb tide and arrive in Tachibana Bay. And when the wind speed is less than 9.7 knot, We found that drifting speed and direction of the mimic driftwood compared with the current speed and direction increased or decreased in 2-3 percent of each segment that we divided the wind vector in two direction. One direction is current direction and the other direction is a vertical segment to the current.

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A field study was carried out to make clear the pattems of flow and water quality changing in a nursery aquaculture pond (30mx 40mxlm) for juvenile flounders, Paralichthys olivaceus, constructed on a sandy beach to utilize wave energy for water exchange. Current velocity, water temperature, salinity, and dissolved oxygen (DO) were measured and a dye diffusion experiment to visualize the flow pattem was conducted. The inflow rate varied according to the sea level and wave height, and the sea water coming from the inlet to the outlet generally created a recirculating flow pattem in the pond. Therefore,.the time, when the maximum values of water temperature and DO concentration occurred, varies with respect to the location in the pond. The DO concentration fell to 60% saturation as a minimum at around 6 a.m., when the inlets were closed. estimated from the DO budget, it was found that the DO consumption rate by all processes in the pond was calculated at 0.162mg/l/hr. About 60% of the consumption was due to the organisms and chemicals which were suspended in the water, about 20% was due to the flounders, and the rest 20% was due to the sediment. The inflow rate of groundwater was relatively small when compared with that of sea water, judging from the salinity budget in the pond.

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[in Japanese]

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