Appropriate escape vent sizes on collapsible crab pot for blue swimming crab (Portunus pelagicus) fishery in Southeast Sulawesi waters, Indonesia

Abstract

Background and Objective: Blue Swimming Crab (BSC) fishery in Southeast Sulawesi faces huge pressure as indicated by smaller Carapace Width (CW) of <7 cm, small biomass of 10-20 ind kg–1, CPUE of 2-3 kg per trip and fishing ground moving further afield. There is no study on selective crab pot for BSC had been done. This study conducted to find out the appropriate escape vent size of crab pots used by fishermen. Methodology: This study used collapsible crab pots equiped with escape vent in the left and right sides in order small sizes have opportunity to escape and return to the sea to grow and attain maturity. Those escape vent sizes of crab pots tested were 4.0×3.5, 4.5×3.5 and 5.0×3.5 cm to find out only BSC of ≥10 cm CW retaine in the crab pots. The BSCs of <10 cm CW escaped from crab pot and gathered into “codend” which was tied in the vent. The BSCs retained in the crab pots and escaped in the codends were measured its CW using caliper, wet weighed their body using electronic balance and identified their gonad maturity and then all recorded in the data sheet. The BSC data was analyzed using “the gear selection ogive” which formulated in the mathematic equation forming sigmoid curve. Results: From three escape vent sizes, the crab pot with escape vent size of 5.0×3.5 cm retained BSC at L50% was 10.74 CW while, L50% of escape vent size of 4.5×3.5 cm and 4.0×3.5 cm was 9.26 cm CW and 8.75 CW, respectively. Conclusion: The curve of gear selection ogive shows that the minimum legal size of BSC at L50% to be recommended is 10.74 cm CW which is found at the escape vent size of 5.0×3.5 cm. This CW has already reached maturity stage and at least once producing eggs.