Analysis of mesh breaking loads in cotton gill nets: Possible solution to ghost fishing |
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| Authors: | Yoshiki Matsushita Shusuke Machida Haruyuki Kanehiro Fumio Nakamura Naoto Honda |
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| Institution: | Faculty of Fisheries, Nagasaki University, Nagasaki 852-8521,;Tokyo University of Marine Science and Technology, Minato, Tokyo 108-8477,;Chiba Prefectural Fisheries Research Center, Minami-boso, Chiba 295-0024, and;National Research Institute of Fisheries Engineering, Fisheries Research Agency, Kamisu, Ibaraki 314-0408 Japan |
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| Abstract: | ABSTRACT: A small number of fishers in Chiba Prefecture of eastern Japan use cotton gill nets to catch Japanese spiny lobster Panulirus japonicus. To examine the advantages of cotton gill nets, we analyzed changes in mesh breaking load of a new cotton gill net used in a fishing operation. A new cotton gill net was also soaked in a seawater tank to simulate ghost fishing conditions. The average mesh breaking load of new cotton mesh was 50.3 N. This value decreased to 19.0 N after 38 days (～912 h), and after 82 days (～1968 h) the mesh could be easily torn (breaking load 0.07 N). Under fishing conditions, the cumulative soak time was only 744.4 h over 19 months. The average breaking load at the end of this period was 43.1 N, a strength 86% that of the presoaked mesh. The mesh breaking load of a cotton gill net continuously soaked for 744.4 h was 26.1 N, as estimated from tank experiment data. Thus, a cotton gill net maintains reasonable strength under typical use conditions, but will degrade if lost at sea. |
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| Keywords: | cotton fiber degradation ghost fishing gill net Japanese spiny lobster mesh breaking load |
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