Effect of towing speed and net mouth size on catch efficiency in framed midwater trawls |
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| Authors: | Kuzuhiko Itaya Yasuzumi Fujimori Susumu Shimizu Teruhisa Komatsu Teisuke Miura |
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| Institution: | Hokkaido Central Fisheries Experiment Station, Yoichi, Hokkaido 046-8555,;Graduate School of Fisheries Science, Laboratory of Marine Environment and Resource Sensing, Hokkaido University, Hakodate, Hokkaido 041-8611, and;Ocean Research Institute, The University of Tokyo, Nakano, Tokyo 164-8639, Japan |
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| Abstract: | ABSTRACT: To investigate fish density using rigid-mouth, towed net gear, such as a framed midwater trawl (FMT), it is necessary to know the catch efficiency. The catch efficiency with an FMT is described as the rate of fish entering the net (entering rate) versus the rate of fish retention, i.e. the mesh selectivity. This study investigated the change in the catch efficiency under several towing conditions using three types of FMT of different net mouth areas (4.0, 12.3, and 16.0 m2) with the same mesh size. The catch efficiency of the FMT was evaluated by comparing catch per unit effort obtained from each towing condition. The catch efficiency of FMT varied with towing speed and net mouth area. Particularly, the effect of net mouth area on the catch efficiency was greater than that of towing speed. Additionally, under the same towing condition, the catch efficiency for large length fish was lower than that for small length fish. |
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| Keywords: | catch efficiency entering rate fish density FMT juvenile young fish |
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