Size selectivity of drum-net traps for whelk ( Buccinum opisoplectum dall) in the Korean coastal waters of the East Sea

The selection of whelk by seven experimental types of drum-net trap was evaluated in a comparative fishing study in the East Sea, Korea, between July and October 2003. The experimental traps were fished in conjunction with a control trap constructed from 20 mm mesh. Three of the experimental traps used increased mesh sizes (35, 55 and 75 mm), another two employed escape rings (diameters of 3 and 5 cm), and the remaining two were constructed using double hoops to form gaps (widths of 2 and 4 cm) around the entire circumference of the trap. The minimum legal mesh size (35 mm mesh) was found to be effectively non-selective over the size range of whelk present in the fishery. The traps with 55 and 75 mm mesh and the traps fitted with escape rings all had statistically significant lower estimated efficiency than the control trap. Although the double hoop traps appear to offer the greatest potential for reducing the catch of undersized whelk, these traps are the most difficult to construct, store and deploy. Further research is required to improve the selectivity of traps fitted with escape rings.