種苗幼魚の計数システムにおいて,光センサを利用して計数する場合にセンサの投・受光面に飛散汚水等が付着し,計数精度が徐々に低下する。そこで,著者らはセンサ投・受光面と計測用管の問にアスビレータを設けた吸引式防汚システムを考案・供試し,アスビレータへの流入量,計測用管の内壁からセンサの投・受光面までの距離,ならびに飛散水滴の大小と本システムの防汚性能との関係について検討した。結果の概要は次のとおりである。 1.連続的な飛散を防止するためのアスビレータ内の流量が134ml/sで98 kPaの負圧を発生できた。 2.飛散防止孔の長さを30mm,同孔内の真空圧差を2kPaに設定すると,落下速度10m/s時におけるセンサ投・受光面への水滴の飛散を防止できるものと推定される。

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資源管理型漁業を実現するため,単船まき網漁業の採算性を定量的に評価する手法を提案した。この方法は,単に漁船の技術面,経営面を扱うだけでなく,水産資源の動的変動を考慮している。この資源の影響は,魚群探索と漁獲の過程において,技術面と関係づけられる。最終的には,漁業としての経営指標と漁場内の資源量の大きさが定量的に示される。さらにこの手法による数値計算によって,乱獲と持続的利用という二つのシナリ.オの例を示した。

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The method to obtain the position of the measurement point by a single satellite applies to the distress rescue and the oceanic observation. The present study analyzed the improvement of the positioning accuracy by the improvement of this positioning method. The analysis was carried out by means of the numerical simulation. The positioning calculation was carried out using the data of intervals of one minute when a satellite approached the measurement point. As a result, When the angle of elevation of the satellite was 80 degrees or less, the positioning error became about 0.2 nm (nautical mile) in the latitudinal direction and about 0.5 nm in the longitudinal direction. This is a remarkable improvement on the accuracy of the usual positioning method.

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We completed the technique to constantly produce the artificial seeds of the short neck clam Ruditapes philippinarum in large scale, because its natural resources have seriously been decreased in Japan. In Yanaguchi Prefecture 10⁷ seeds of 1-2mm in shell size have been able to obtain in a 100 m³ tank from 1992, and about 2 × 10⁷ seeds were produced annually. For incresing the survival rate of the released seeds, the intermediate culture of them unti1 10mm in shell size was carried out mainly by Yamaguchi Prefectural Fisheries Station and ten Fisheries Cooperative Associations. The large scale seed production of this clam and its intermediate culture are described in detail. We, furthermore, present the results on the production of the seeds bearing a special color pattem on the shell as a marker of the released seeds. Bp (banded purple) type shell, Which is very rare in the fields, could be fixed genetically by the group and individual inbreedings. In 1996 we obtained the fourth generation of the Bp type shell at the rate of 92.5 % in the group inbreeding experiments and nearly 100 % in the individual inbreeding experiments. A pert of them were released to the fields after the intermediate culure.

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It is known that verical vortices of various sizes distribute in the sea and those vortexes are closely comected With vertical circulation of sea water and the matter diffusion of the bottom in deep sea from the latest marine observation and the numerical analysis. This paper shows the numerical method of the two types rotating flows based on the Navier-Stokes momentum equation, and estimates the velocity intensity in the bottom boundary layer and shows that the upwelling depends on the those results.

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