著者

津村 良祐 木村 暢夫 藤森 康澄 岩森 利弘

出版者

北海道大学大学院水産科学研究院 = RESEARCH FACULTY OF FISHERIES SCIENCES, HOKKAIDO UNIVERSITY

雑誌

北海道大学水産科学研究彙報 (ISSN:13461842)

巻号頁・発行日

vol.57, no.1-2, pp.19-24, 2006-11

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Ship motions on the small fishing boats for scallop cultivation in Funka-Bay, Hokkaido, are usually influenced by the dynamic force of large scale cultivation facilities. On the rough sea condition, it would generate fatal ship motions like large amplitude rolling motion. To reduce such ship motions under fishing conditions, we designed a new type of mooring device with buffer materials used as absorber for ship motions. We carried out the tank experiment used the model in the wave conditions corresponded to the actual fishing operation to confirm the effect of reducing ship motion. For the waves in the long-period frequently generated under rough sea, the damping effect of the absorber was effective to reduce rolling motion, and accounting for nothing less than 10.0% compared with the normal mooring device without the absorber. As a result, the mooring device with absorber is effective for the improvement of seakeeping qualities of the fishing boats for scallop cultivation.

著者

東海 正 大本 茂之 藤森 康澄 兼廣 春之 松田 皎

出版者

日本水産學會

雑誌

日本水産学会誌 (ISSN:00215392)

巻号頁・発行日

vol.63, no.5, pp.715-721, 1997-09-15

参考文献数

19

被引用文献数

6 3

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A separator-trawl used for a mantis shrimp catch in Tokyo Bay has a separator panel and two codends; separator net-panel (100mm stretched mesh length) on part of the top of the first codend (62mm mesh length) which is covered with the second codend (33.6mm mesh length). The fishermen hoped mantis shrimp as a main target species would be caught in the second codend and be separated from starfishes retained in the first codend, because large amounts of starfishes cause difficulty in fishermen's hand-sorting on deck. Separation efficiencies of the trawl were obtained from the catch numbers in the two codends in a fishing experiment. Separation efficiency between species <i>i</i> and <i>j</i> is defined as γ<i>_i</i>+γ<i>_j</i>-1, where γ<i>_i</i> is the recovery ratio in the codend for <i>i</i>-species, that is, a proportion of the <i>i</i>-species catch number in the <i>i</i>-species codend. While the recovery ratio for starfish in the first codend was 0.96, that for mantis shrimp in the second codend was 0.66 which was not so high as expected. Thus, separation efficiency between mantis shrimp and starfish was 0.62. Although the separator net-panel has enough large mesh size for small animals, e.g. small crab <i>Carcinoplax vestina</i>, some species of low swimming ability failed to pass through the separator panel and were retained in the first codend. This implies that separation performance of the separator-trawl depends on the swimming ability of each species in the net as well as mesh selectivity of the separator net panel.