In pelagic longline, deploying the gear such that the depth of the hook is the same as that of the target fish is important to improve the fishing performance and selectivity. In this study, the depth of the tuna longline hook was estimated using the mass-spring model, catenary curve method, and secretariat of the pacific commission Pythagorean method in order to improve the performance of the longline gear in Fiji. The former two methods were estimated to be relatively accurate, and the latter showed a large error. Further, the mass-spring model accounted for the influence of tidal current in the ocean, which was found to be appropriate for use in field trials.

• Viliame BAINVES(Ministry of Fisheries, Central Division, Main Street)
• Chun-Woo LEE(Division of Marine Production Management, Pukyong National University) Corresponding author
• Subong PARK(Department of Fisheries Physics, Pukyong National University)