In order to elucidate the influence of large winter waves on the mortality of Japanese littleneck clams(Ruditapes philippinarum), we conducted surface exposure experiments using seawater tanks in summer and winter. Clams were manually exposed to the seabed surface with different frequencies, and their burrowing rate, glycogen content and condition factor were found to be negatively correlated with the frequency of the exposure in both seasons and the values were lower in winter than in summer. These results show that repeated surface exposure reduces glycogen content and condition factor and results in a lower burrowing rate. Moreover, its influence is more severe in winter. In the winter experiment, some clams on the surface burrowed and then crawled out. The clams that crawled out had much lower glycogen contents(less than 10mg/g), than those that burrowed, indicating that they were weakened. These results suggest that exposure to large winter waves leads to the death of the clams.

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漁船員の労働災害は全産業の8倍と被災率が高い。人間工学的には,多くの漁業労働災害が不十分な作業環境に関連して発生している。本研究では,漁船労働で最も災害発生率が高いまき網漁業を対象とした。漁労作業時の作業者の作業動作をビデオカメラで記録して,作業安全に影響する作業者の動作分析を行い,人間工学の観点から危険要因の研究を行った。まき網漁船の作業者の動作,作業姿勢を分析した。不自然な作業姿勢が見られ,「つらさ指数」によって評価した。網を上げる作業では,二台のドラムを一人で操作した場合,「つらさ指数」4以上と評価され,改善が必要である。

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This paper deals with a problem of squid sucker adsorption as an obstacle to the collecting operation after catching squid. First, the adsorption mechanism is clarified and a model of single sucker's sucking force is built Next, by the mechanical model of a squid on the collecting chute constructed in this paper, each physical parameter and friction force due to sucker adsorption of live squid are measured. Then, the required velocity and the required flow rate are derived from the mechanical model as mechanical conditions that allow smooth squid flowing. Based on these results, the influence of sucker adsorption to the collecting operation is evaluated quantitatively, and it is confirmed that sucker adsorption is a serious problem. Furthermore, using the required velocity curve, a systematic method of choosing flow rate and setting suitable velocity for the rate is proposed.

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The trawling system equipped in the NANSEI MARU is composed of two parts. One displays positions of the ship and the fish school. The other controls fishing gear. This system was applied for the purpose of evaluating the length distribution of the fish school, and monitoring the position and the configuration of fishing gear. Its goals are optimizing the fishing gear configuration during towing and confirming a capture of fish school. This system was installed in the newly constructed training ship NANSEI MARU(175 G.T, 1323 kw) in Faculty of Fisheries, Kagoshima University. This system consists of scanning sonar, quantitative echo sounder, trawl sonar, and automatic tension controlled trawl winches system. The automatic tension controlled trawl winches system controls the length of warp for optimizing the configuration of fishing gear to its optimum condition. The fish schools and the fishing gear are searched with the scanning sonar. The trawl sonar measures the depth, the horizontal and vertical spread of the trawl net. The relative positions of a trawl gear and depths of otter boards are indicated on the scanning sonar screen by the signal from the transponders, which are located at the otter boards. The data on the fish schools and the fishing gear, such as relative direction, the depth and the distance, are sent to the computer. The computer system integrates these data and shows information on the positions of the fish school and the fishing gear on the display screen. It can also display a three-dimensional image on the screen from various viewpoints. The skipper can direct the trawl gear towards the fish school by manipulating the warp length and the towing speed while watching monitor screen. This trawling system showed satisfactory performance during the field experiment.

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The survival test of Ruditapes philippinarum was carried out in Lake Nakaumi, to clarify the reason why the clam could not increase in this brackish lake recently. Five transect lines were designed in Lake Nakaumi. Three containers with R. philippinarum were set on the lake bottom of each transect line, with the depth of 1.5m, 2.5m and 3.5m. All clams on the lake bottom of 3.5m in depth died soon after the start of the experiment. All clams in the west side of the lake also died even on the shallowest. In contrast, clams in the east part of the lake survived through the summer, while the clams along the trench died finally in autumn. The environment of the shallow bottom was evaluated based on the survival test and current distribution of the clam. The result suggests that the lower oxygen and anoxic lake water developed by the construction of embankments and dredging for reclamation is one of the main limiting factors for the R. philippinarum in Lake Nakaumi.

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橘湾タチウオ漁場の成立条件を,水質の漁場環境条件とタチウオ漁況との関係から見出すことを目的に,周年の漁場環境調査を開始した。本研究では,海洋の水質および潮流観測結果を数学行列計算ソフト"MATLAB"の機能を応用して,迅速かつ独自の表示法の開発を行い,その試験的運用を試みた。その結果,"MATLAB"によるGUIの機能を用いることにより,毎回の定期観測,観測項目毎および各定線毎の季節変動の一括表示などにおいて,ユーザーの要求に応じた処理が瞬時に行えるようになった。この点,"MATLAB"によって構築したオリジナルソフトを活用することにより,海洋観測結果の表示に関して,十分有用な手段になり得るものと認められた。

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In this report, applicability of some regression formulae of ship wave-making resistance to fishing vessels is examined. As a method suitable for the fishing vessels, a regression formula based on the immersed body approximation, which is one of the wave-making resistance theory, is proposed. Applying three formulae to the UBC trawler series model experiments, the regression formula based on the immersed body approximation gives better estimation results compared with Tagano's formula based on the thin ship theory and Calisal's formula based on the Havelock's two dimensional wave interaction model.

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Fisheries Engineering has served for changing an oceanic environment into an ideal one for marine ecosystem aimed to secure and increase marine fisheries resources, and has witnessed a rapid development during the last 40 years, and has been involved in the project to establish Artificial Reefs and develop the proliferation site for juveniles of fish and shellfish. The marine fisheries resources in the Sea of Japan are largely classified into large-sized wandering fishes coming over from the East China Sea on one hand, sardines and bottom fishes undergoing repeated reproduction process in the Sea of Japan on other hand. The changes in these resources are closely interlinked with oceanic environment, but the haul of fishes has been rapidly on decline, with its peak experienced in around 1990. Especially, sardines have remarkably decreased. The reason behind this trend has not been identified. According to the statistics on fisheries, the production of bottom fishes has been almost stable. I guess that Artificial Reef works well for the production of these bottom fishes. Since the waters on the Sea of Japan flow across coastal borders, nutrients are released from the shore, and the surface layer of the waters is poor in nutrient. It is well known that huge rapids and shallows scattered around every parts of the Sea of Japan coast constitute ecological system and function as a good fishing ground. In these rapids and shallows, topographical upwelling emerges and becomes the source of supplying nutrient-rich waters of deep- sea bottom layer to the outer layer of the sea. In order to sustain and increase marine resources in the Sea of Japan in a stable fashion in the future, it is quite essential for us to achieve a stable circulation of a food chain system. It is also necessary to explicate the mechanism of how topographical upwelling arises and develop the artificial upwelling applying topographical upwelling.

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We monitored an artificial eelgrass bed planted on an artificial tideland on the coast of Hinase-cho, Okayama prefecture. The distribution of eelgrass was monitored in September 2003(four years after construction of the bed), revealing that the bed had expanded from 50m^2 to 1,000m^2 in four years. This finding shows that the creation and cultivation of artificial eelgrass beds requires the improvement of environmental conditions through such civil engineering interventions as raising a sandy bottom to a gentle slope.

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Blue sprats Spratelloides gracilis are mainly caught by the stick-held dip net and the drift gill net. This paper was described these fishery production processes on fishing method to landing of fishes in Hokusatu district in Kagoshima prefecture. Blue sprats caught from two kinds of fishing method have different demands, one is for the processor and another is for fresh fish. Therefore, both fisheries are coexistence relation in the district. The stick-held dip net fishery usually requires sorting work for fishes. A case of far from fishing ground to unloading port, it should be introduced cooperative transportation of each boat's fishes in the drift gill net fishery. Introductions of the labor saving measures based on the work analysis of the fishery production process are necessary for improving the management of the fishery household.

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