Catch comparison between small- and commercial scale of collapsible pot fishing targeting blue swimming crab (Portunus pelagicus) in the upper gulf of Thailand
2011
Anukorn Boutson(Kasetsart University, Bangkok (Thailand). Faculty of Fisheries. Department of Marine Science) E-mail:[email protected] | Takafumi Arimoto(Tokyo University of Marine Science and Technology, Tokyo (Japan). Fish Behavior Section)
Catch field surveys were conducted by on-boarding both for small- and commercial-scale boats in the upper Gulf of Thailand in 2006-07. The small-scale operates inshore (0.5-3.0 km) by one man operation, with individual pot setting of 295-367 pots/boat. The commercial-scale operates offshore (GT 3 km) by 5-8 crews with long-line type setting of 1,687-2,120 pots/boat. The catches were analyzed in CPUE, catch composition, bycatch and discard by number. They were also compared from the view point of operation strategies as fishing ground, method, soaking time, etc. Average CPUE for the small-scale was 2.81 crabs/pot, which was much higher than the commercial-scale of 0.26 crabs/pot. Catch composition of blue swimming crab for small-scale accounted for 72.4-91.3 percent while 21.2-51.6 percent for commercial-scale of total catch. Average discard ratio for small and commercial-scale were 0.30 and 0.50, whereas average discard rate were 0.22 and 0.30, respectively. The crab size caught for small was smaller than commercial scale but bycatch for commercial scale was higher. The results showed that the bycatch for both types of operation require the mitigation measures for selectivity improvement.
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