Size selectivity of the red queen crab trap estimated with pocket cages
2006
Watanabe, T.(National Research Inst. of Fisheries Engineering, Hasaki, Ibaraki (Japan)) | Yamasaki, S.
To estimate the size selectivity of the trap for the red queen crab Chionoecetes japonicus without control traps, fishing experiments were conducted with commercial traps modified with pocket cages. The pocket cage was box-shaped, consists of iron rod frames and netting. Two pocket cages were fixed symmetrically on the side of a trap and these cages covered a part of the netting and the circular escape vents (100 mm inner diameter). Soak time was approximately 2 days. The size frequency distributions were obtained from catches of traps, pocket cages on the netting and pocket cages on the escape vents. The size selectivity curves of the trap and the vented trap were estimated by the SELECT model using the likelihood of a multinomial distribution from the proportions taken in the trap and pocket cages catch to the total catch of each carapace width class. The 50% retention carapace width of the trap and the selection range (difference from 75% to 25% retention carapace width) were estimated to be 89.4 mm and 7.2 mm, respectively. This estimation method using pocket cages is practical, because size selectivity can be estimated, even though the operation frequency and fishing effort are small.
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