Nippon Suisan Gakkaishi 65 (1), 3-10 (1999)

Accumulation Process of Distant Water Small Trawl in the North Pacific Ocean Estimated on Pocket-net Experiments

Yoshiki Matsushita,*1 Yoshihiro Inoue,*1 and V. A. Tatarnikov*2

The experimental operations were carried out by a distant water small trawler in the North Pacific Ocean to research accumulation process for walleye pollock Theragra chalcogramma and atka mackerel Pleurogrammus monopterygius in the trawl. Fourteen pocket-nets were attached from wings to the codend to investigate how fish accumulate between the net mouth and the codend. When the pocket-nets were attached over the trawl netting, the pocket-net catches were extremely low, suggesting a blocking effect by the trawl netting for both species. When the trawl netting was removed from the pocket-net mouth, a catch of the pocket-net was relatively large at the rear part of the trawl for both species. The pocket-net attached at the side panels had a tendency to catch more fish than the pocket-net at the top panel. Two models to express accumulation process were developed from catch results and trawl shape assuming that no fish passed through mesh. Those are; Model 1, Density of fish become higher at the near space of the netting due to the accumulation along the netting; Model 2, Density of fish become higher uniformly in any cross section parts. Correlation between density of fish estimated by Model 1 and catch of the pocket-net was higher than the case of Model 2 for both species. This suggests that the accumulation process was mainly governed by trawl shape and both species were accumulated to the codend along the netting by the taper construction of the trawl.


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