In order to maintain the Sargassum confusum population, reproductive cycle of the S. confusum and grazing pressure by the sea urchin were observed monthly in Suttsu, Southwestem Hokkaido, Japan, from 1996 to 1998. Fruiting period of S. confusum is July and August. The grazing pressure related with decreasing of juvenile S. confusum (less than 0.2 wet g/individual). To protect the juvenile S. confusum in decreased population, sea urchins were fished before the fruiting season. After fishing, biomass and individual density of the S. confusum population promptly increased. By management of fishing season of sea urchin, the S. confusum population is able to maintain sustain productive fisheries ground.

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Environmental variables (light irradiance, temperature, salinity, turbidity, and chlorophyll a) in relation to macroalgal distribution were analyzed bimonthly from April 2001 to February 2002 in Hiroshima Bay. Three dominant species of brown algae, Sargasstm horneri, S. macrocarpum, and Ecklonia kurome grow at each different depth 0-1m, 1-3m, 3-9m, respectively. The environmental gradient from the inner to the outer part of Hiroshima Bay in the vicinity of the seaweed beds as well as along the center of the bay was surveyed. The suspended matter that originates as effluent from the Ohta River is suggested to lead to a decrease in the light attenuation. The quantities and the properties of suspended matter changed seasonally and varied between each seaweed bed. The attenuation coefficient is suggested to be influenced by the suspended matter concentration and the effects were much larger in the imer part of the bay than in the central and outer parts. The three dominant brown algae were distributed along the environmental gradient in Hiroshima Bay. The two sample Hest of environmental variables of temperature and salinity showed significant differences among the species, except for light irradiance. This means that light conditions might not restrict the distributions of these algae. This study concludes that other environmental variables might be important to detemine their distribution, even though macroalgae can acclimate to environmental changes.

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On the basis of observation data of water temperature and salinity at Uranouchi Bay during the convection period, the heat flux of sea surface cooling, the potential energy given to the water column by the heat flux, and the dissipation energy are estimated. The diameter and the circumference speed of the maximum convection eddy caused by surface cooling are also evaluated. These results are described as follows : ① The heat flux through sea surface is 130(Jm^-2s^-1) in December. It's almost the same as the estimation about Mikawa Bay by other methods. ② The potential energy per unit time (de_Q/dt) given to the water column by the heat flux is (4-17) × 10^-5(Jm^-3s^-1). More than half of de_Q/dt tums to the potential energy of water column, and the remainder turns to dissipation energy (thermal energy) and disappears. ③ The diameter of the maximum convection eddy caused by surface cooling is about 0.4 (m). The circumference speed of the eddy is about 0.001 (ms^-1).

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The heart rate of a red sea bream (F.L. 43.3cm, B.W. 1.3kg) was measured using a heart rate ultrasonic transmitter developed by the authors. A heart rate over 80 bpm (beats min^-1) was observed just after release into a fish pen. Then, the heart rate gradually came down and finally settled between 50 bpm and 60 bpm after 21 hours. This agreed with the standard heart rate estimated by applying the relationship between heart rate and ambient water temperature obtained in laboratory trials. The first 21 hours was a period of recovery from trauma caused by tagging and anesthesia treatment.

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The bottom sediment, benthic community, fish and larvae of commercial shellfish species were investigated at an artificial tidal flat in Mikawa Bay, Japan. Differences between low and high tidal flat areas were investigated. The central area of the development was comprised of fine sand, whereas fine sand and coarse sand were present in the original bottom of the tidal flat. Organic matter content was high in the waterway and the marginal area of the development. The water purification rate, in terms of macrobenthic biomass, was high in the central and marginal areas of the development. In contrast, biodiversity in terms of macrobenthos species abundance was low in the central area of the development. Thus the distributions in the water purification rate and biodiversity were different. Mactra chinensis, Mactra veneriformis, and Ruditapes philippinarum dominated the commercial bivalve species at different heights of the tidal flat. Platichthys bicoloratus dominated the fish larvae of commercial species, and distribution across defferent depths varied according to body length. The marginal area of the development was important for settling larvae. As distributions of dominant species and functions of the tidal flat are different, we suggest that it is important to ensure a range of consecutive depths when creating an artificial tidal flat.

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Daily catch data of coastal squid jigging boats, their light source output for fishing lamps and monthly mean wholesale prices of squid were collected from five fishing ports (Hakodate, Sado Island, Noto, Sakaiminato, and Tsushima) in Japan, for a purpose of evaluating optimum light source output, which created a maximum economic yield. The daily income were estimated from the relationship between daily catch data and monthly mean wholesale prices of squid. Then, the optimum light source output was calculated from the relationship between daily income and daily lighting expenses by each fishing management conditions. The results show that daily income and daily lighting expenses were significantly increased as light source output for fishing lamps were increased. The lower light source output which obtained by each fishing management conditions was advantageous when lighting cost become more expensive or wholesale price become cheaper then ever.

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This paper proposes the advanced rudder roll stabilization controI system with hybrid fin controI system based on multivariate auto-regressive model. To confirm the effectiveness of Fin and Rudder Multivariate Hybrid System, full scale experiments were conducted by using prototype hybrid control. Research and training vessel 'UMITAKA-MARU' of Tokyo University of Fisheries was used for experiment. The full scale experiments included measurement of roll angle, roll rate, heading, rudder angle and fin angle. The rudder roll stabilization system, fin stabilization system and hybrid stabilization.system were carried out for the experiments to compare the effectiveness of each system. Statistical analysis was used for the time series data obtained from experiments and the results show that the hybrid controI system with fin and rudder has good performance for reducing rolling motion and keeping course.

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An analysis of assumptions about short-term statistics and wave height during special circumstances, the passage through Tokyo Bay of Typhoon ♯15 in 2001, and Typhoon ♯21 in 2002 is presented based on measurements in actual field. The water surface elevation was measured using wave height meters based on micro Doppler radar that were equipped on Tokyo University of Fisheries’research and training vessels Umitaka-Maru and Shinyo-Maru. Data describing the actual sea during passage of typhoons were analyzed to explore wave characteristics. It was confirmed that conventional methods of short-term statistics for wave height applied to the prediction of significant wave height and highest wave height were satisfactory for the safety operation of ships and fishing boats. However, it was also found that the P-M wave spectrum camot easily be applied to the shape of the spectrum or to the high frequency characteristics of the actual sea during the passage of a typhoon.

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The Kinematic Global Positioning System is used to derive high accuracy positioning data. This paper presents an analysis of the accuracy of horizontal baseline vector due to adding error of 20m in the position of the reference station. The positioning was computed by post processing software. It is shown that the error of the horizontal baseline vector is in proportion to the accuracy of the position of the reference station. The error is reduced to less than approximately 2cm when the baseline length is less than 10km. In addition, when the position of the reference station contains a height error, the error of the horizontal baseline vector is very small and exhibits a fixed tendency. Empirical fomula to calculate the horizontal error of the user station is presented.

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Based on the results of the previous two reports, we attempted to inhibit the accumulation and proliferation of marine fouling organisms on vinyl plates through the application of a weak electric current via titanium wire electrodes. Plates were set in two sea areas near the National Fisheries University ; one area was subjected to an electric current, and the other area was used as a control. The experiment was carried out over two periods ; June to August 1999 (3 months : 1st period), and October to January 2000 (3 months : 2nd period). using solar cell modules and rechargeable NiCad batteries, we supplied a constant current of about 70 mA at 5 V during the .first period the same as in 1998. We used only solar cell modules during the second period. The application of 70 mA at 5 V was found to be effective in preventing the adhesion of bamacles through a year. It was estimated that the time of the voltage larger than 8V, which is expected to be effective to prevent fouling by seaweeds from the result in 1997, had been applied during the second period was about 5.3 hours a day. Hence it was clarified that such electrical conditions were not effective to prevent fouling by marine organisms. We should confim the prevention of fouling under the condition where a voltage larger than 8 V is always applied and also clarify the affected area by the electrical conditions.

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In order to protect the snow crab population a crab sanctuary was established. An Untethered Remotely operated Vehicle was used to gauge crab population numbers in the protected area and an unprotected area (reference point) between the years 1996-1999. UROV results conclude higher crab densities in the protected area each year of the test. Protection efforts were effective.

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