Catch efficiency and size selectivity of collapsible crab traps using green vs red nets and large vs small mesh sizes

Abstract

Collapsible crab trap is a popular fishing gear among small-scale swimming crab fishers along the coast of Thailand. This project is to evaluate catch efficiency and selectivity between the collapsible crab traps using green vs red nets and between those using small 0.75 cm vs large mesh sizes 2.50 cm, including its potential impacts of the collapsible crab trap which has the different colour nets and mesh sizes, on swimming crab stock. Our results revealed significant differences of the efficiency and size selectivity between the traps with green and red nets. The trap with red net , 0.47 no.crabs / trap-days, was more efficient than the one with green net, 0.21 no.crabs / trap-days, as its catch per unit of effort (CPUE) was higher. In addition, the crabs caught by the red net trap were larger 4.31 cm than those caught from the green net trap 4.14 cm and were in a wider size- rang. Differ from the net color, small (0.75 cm) vs large (2.50 cm) mesh size had no effect on the efficiency. The CPUEs obtained from the trap with small and large mesh sizes were indifferent : 0.40 and 0.35 no.crabs / trap-days, but different size selectivity. The catches from the trap with small 0.75 cm mesh size harvest the smaller swimming crab, 3.61 cm than those from the traps with large 2.50 cm mesh size 3.79 cm, but various sizes.