The mechanism of fishing was clarified for salmon drift gill net of the northern sea at fishing course. The method of obtaining a new original fishing selection curve from a dynamic condition when the fish was maintained in a mesh was designed, and the factor that influenced the fishing selection by the numerical analysis was investigated. The relation between a size and a proper diameter of the mesh of the gill net was examined. The analysis of the fishing mechanism of shell dredge that caught the shell dove in sand and lived was advanced, the probability model by which the shell did not get out from the packing part and the bag net part was set, and selected curve of shell dredge was presumed.

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GPS has become an indispensable tool in fishery by fishing boat recently. A positioning accuracy (horizontal deviation: 2DRMS) has been 15.9m by SGPS and 4.5〜6m by DGPS in case of HDOP is 1.5 after cancellation of selective availability (SA). The positioning accuracy improved 10 times as compared with after GPS started. Although GPS is such a convenient tool, the main usages of fishery are safety navigation and search of fishing point. In this paper show that a possibility of the application to the monitoring of a movement of fishing gear and the management fishery by DGPS.

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Unlike other vessels, fishing boats and similar small boats of less than 19 gross tons are subject to large angle amplitude oscillations even at wave heights of 1 m or less. Therefore, estimation of wave height is important for discussing the seakeeping qualities of small boats. In the present study, the authors propose an estimation method based on fetch and wind velocity by constructing an input/output system of sea area characteristics from the Radial Basis Function Network Model and then compare it with conventional estimation methods to determine the accuracy of estimation. Consequently, the method proposed in the present study showed more accurate estimation results.

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Along the Okhotsk Sea coast of Hokkaido, the scallop (Patinopecten yessoensis) seabed sowing cultivation has been successfully performed with the four-year cycle system of mariculture. The scallop aged four is caught by the pair of dredge nets of a 14GT size vessel. However, scallop dredging operation consists the cycles of the strenuous works, such as the dredge net hauling, emptying and sorting of the catch. In this report, the author explained the field investigation of the scallop dredge fishery conducted in Tokoro fisheries cooperative association. And a method for simulating the dredging operation was developed with consideration of the cumulative catch in the fishery ground. It showed that scallop catch efficiency decreases remarkably as the cumulative catch become close to the initial stock. The relationship between the scallop dredging operation characters and the cumulative catch could be evaluated from this calculation model.

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In order to construct the recycling system of fisheries tray, it is necessary to assess the cleaning effect. In this paper, a starch solution is used to make artificial fisheries tray that has homogeneous stain. According to the characteristic of starch and iodine, the cleaning effect can be measured with image processing by analyzing the relationship between the residue and total stain. Moreover, in order to confirm the evaluated accuracy of cleaning effect, a weighing method is used. And it is obvious that the result of the measurement with image processing is actually the same as those of weighing one. As a result, the evaluating method of stain elimination rate, with practicability, economics and high accuracy, is developed. The following results are obtained : 1) The accuracy of measurement with image processing is high. 2) The cleaning effect can be assessed in detail with image processing, and it is useful for controlling the cleaning condition. 3) Compared with a conventional method, the method with image processing is simpler and costs less time.

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Catamarans have wider deck area and larger transverse stability compared to monohull ships. For fishing vessels, since these features are great advantages, catamaran hull form is a promising. Most of problems in the design of the catamaran are related to the seakeeping performance. Therefore, it is necessary to examine the seakeeping performance by the numerical calculation in the design of fishing catamarans. In this report, the calculation methods based on a strip method and results of seakeeping performance of fishing catamaran are presented. In addition, the outline of a constructed fishing catamaran is also described and problems and future tasks are addressed.

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Based on the severe indication concerning the enforcement of the suitable evaluation, the reservation of the transparency, etc. to public works, the evaluation concerned mainly with the cost-benefit analysis is carried out in each public work in recent years. However, when it stands on a national viewpoint, it is important to explain synthetically the effect which the concerned public works brings, such as the benefit to the local economy and to the consumer. For this, reason the measurement point of the effect, fishing port improvement work brings, in a series of process from landing of a marine product to consumption was proposed and the quantitative grasp of the benefit by the improvement work of Kesennuma Fishing Port in Miyagi prefecture was tried.

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In this study, we introduce a convenient method of swimming mechanism analysis of largemouth bass using a digital video camera (DV). To understand both mechanisms in steady and burst swimming, two experiments were conducted. Fish were made to swim in a flow tank to understand the steady swimming mechanism and were given prey in an aquarium to understand the burst swimming mechanism. Nine fish were made to swim in the flow tank in different water velocities and swimming forms were recorded by a DV. The fish swam with stable frequency and amplitude of tail beat at a range of water velocity from 1.17±0.16 to 1.88±0.24 TL sec. whereas, the fish beat their tails strongly a few times and then momentarily rested at a range of water velocity from 1.88±0.24 to 3.29±0.92 TL sec. The tail beat frequency increased with the rise in water velocity whereas the tail beat amplitude did not have significant relation to the water velocity. One fish was given a gold fish as prey in an aquarium and two DVs recorded lateral and anterior views simultaneously during the foraging behavior. Just after recognition of the prey, the fish accelerated and came close to the prey. Maximum swimming speed and acceleration reached 5.8 TL/sec and 8.5m/sec^<2.> respectively. These results show the high potential of the power of largemouth bass in exchange for not having much endurance. This alternative performance reflects the predatory strategy of largemouth bass. Although all results showed fundamental and general swimming mechanisms of fish, this convenient method using DV could be used to describe the swimming mechanisms accurately.

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To increase catch efficiency, it is necessary to understand the habitat utilization of the target fish around fishing gear. A biotelemetry study using coded ultrasonic transmitters and set receivers was conducted to understand the habitat utilization of largemouth bass around a set net in Lake Biwa, Japan. Three receivers were installed on leader nets of the set net at short intervals by design to understand the fine scale movement of fish. Four fish were implanted with a coded ultrasonic transmitter and released near the set net. Two fish were monitored for over 50 days and showed diurnal habits. Just before the fish left the set net. the main current direction was southwestward and the current velocity was over 5m/sec. In a set net fishery, current profile is an important factor affecting the concentration and dispersion of the target fish.

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Immature Pacific bluefin tuna, Thunnus orientalis, marked with archival tags, were released off Tsushima Island in the East China Sea. Time-series data on swimming depth, and ambient and peritoneal cavity temperatures were recorded every 128 s to investigate their thermoconservation mechanisms under low ambient temperature. In summer the difference between peritoneal and ambient temperatures became appreciably large, as ambient temperature decreased due to repeated dives to depths below the thermocline for short periods, perhaps for feeding. This suggests that peritoneal cavity temperature is maintained during dives. A heat budget model revealed that thermal inertia, or internal heat production in the daytime, was important for thermoconservation during dives to depths below the thermocline. As bluefin could only maintain body temperature for a short period, they had to avoid rapid temperature change at the thermocline through behavioral thermoregulation. This is quite different from the situation for bigeye tuna, as reported elsewhere. In addition, it was also revealed that vertical diving activity could be related to physical conditions such as light intensity. The bluefin made few dives on days when solar radiation was comparatively low, implying that low visibility may prevent dives to depths below the thermocline.

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For quantitative assessments of the effect of artificial reefs to accumulate fish school. we developed a low cost fish school monitoring system (FISCHOM). which enables visual and acoustical observation of fish resources for more than several days. In this paper, we report the profile of prototype FISCHOM and the outcome of trial survey. FISHCOM is consisted of two sensors (a stereo camera with two strobe lights and an echo sounder), a programmable timer, a battery, and a pressure resistant housing with a visually and acoustically transparent window for the sensors. All components except for the housing were selected from inexpensive articles on the market. A digital camera captured two visual images apart 50 cm away each other, which was combined together by a stereo photogrammetric mirror. The stereo images enable us to measure the three-dimensional information of fish school (e.g. fish length tilt angle, distribution). Two sensors acquire a set of data every optional interval (from several seconds to hours) controlled by the programmable timer. A trial survey was carried out at a high-rise artificial reef located off Atsumi, Yamagata prefecture on May 2003. FISCHOM succeeded a 5 days monitoring with an hour interval of data acquisition. We obtained a time series data of individual number of fish, fish length and distance from FISHCOM by the stereo camera, and fish school distribution by the echo sounder. We have demonstrated that the FISCHOM is appropriate to obtain quantitative and continuous data of fish school than other observation methods, which commonly used for the artificial reef assessment, such as observation by SCUBA diver, angling sampling and fish echo sounder operated on a boat.

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The Heart rate and the activities of a red sea bream were measured simultaneously in a saltwater pond. The heart rate was measured using an ultrasonic transmitter. The activities including 2 axes acceleration, swimming speed and depth were measured using a data logger. After sunrise, the fish became active and the heart rate showed 8% increase. Applying the relationship between metabolic rate and ambient water temperature obtained in laboratory trials, the oxygen consumption and the out put volume were estimated to have 18 and 10% increase, respectively. The estimated metabolic rate by applying the equation of motion was an overestimate considering the energy efficiency. While the fish dashed and cruised with tail beat frequencies at 3.8 and 1.8 Hz, respectively, the heart rate was stable.

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Waves are known to be one of the factors to influence the distribution of the seagrass and seaweed beds. The wind environment, which is one of the effective conditional factors of wave formation were investigated over a ten year period (1992-2001) in Hiroshima Bay to clarify the characteristics of the distribution in Hiroshima Bay to clarify the distribution of seagrass and seaweed beds. The index of the wind environment was analyzed based on the frequency of wind direction, velocity of the wind, and force of the wind. In this research, the wind force was estimated by accumulating the value of the third power of the velocity of the wind, and the effect of wind conditions were compared between the northern coasts and the southern ones. The results showed that the wind parameters, frequency of the wind direction, velocity of the wind, and force of the wind were larger in the wind direction of north or north-northeast than other wind directions. Moreover, the force of the northern winds (from NNE to NNAV) was higher by about five times than that of the southern winds (from SSE to SSW). These results suggest that coasts facing the north were more susceptible to force of the wind than coasts facing south.

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