Use of escape vents to improve size and species selectivity of collapsible pot for blue swimming crab <Emphasis Type="Italic">Portunus pelagicus</Emphasis> in Thailand |
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Authors: | Anukorn Boutson Chaichan Mahasawasde Songsri Mahasawasde Suriyan Tunkijjanukij Takafumi Arimoto |
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Institution: | (1) Graduate Course of Applied Marine Biosciences, Tokyo University of Marine Science and Technology, Tokyo 108-8477, Japan;(2) Department of Marine Sciences, Kasetsart University, Bangkok, 10900, Thailand |
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Abstract: | Laboratory experiments were firstly conducted to determine the possibility of modification of the collapsible pot for blue
swimming crab Portunus pelagicus by designing appropriate escape vents in terms of shape, position, and size to improve size selectivity by reducing the catch
of immature crabs. In laboratory observations, nearly square-shaped vents of 35 mm height and 45 mm length, located at the
lower part of the side panel, showed the best performance to allow the escape of immature-size crabs by side-crawling escape
behavior through the vents, with L
50% selection carapace length (CL) of 39.1, 44.4, and 48.7 mm CL for 40, 45, and 50 mm vent length, respectively. Comparative
fishing trials between conventional and vented pots with vents of 35 × 45 mm size were conducted to examine the crab size
and species selectivity. Use of the vented pots was found to reduce the number of immature crabs in the catch from 70.5% to
11.0% on average, while not affecting the catch efficiency of mature-size crabs. The vented pots also had a selective effect
for reducing the catch of bycatch species in comparative fishing trials. |
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Keywords: | Blue swimming crab Bycatch Discard Escape vent Portunus pelagicus Pot Size selectivity Species selectivity |
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