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Mesh-selectivity of Drift Gillnet on Skipjack Tuna (Katsuwonus pelamis) Operated Offshore Pelabuhanratu Waters, West Java
Abstract:
Skipjack tuna (Katsuwonus pelamis L.) is an economically important marine fish caught in the waters of Indonesia. The objectives of the study were to (1) investigate the effect of mesh size on skipjack tuna, its composition, weight or length and body girth, and ways of being caught (snagged, gilled, wedged, or entangled); (2) determine skipjack gillnet selectivity based on Matsuoka (1995)* method that has more advantages than other methods because it examines the fish capture process; and (3) investigate the maturity status of fish that are caught by drift gillnet as one technical aspect in developing recommendation for the management of skipjack tuna resources.
The study was conducted from June to October 1999 in Pelabuhanratu Sukabumi. Activities consisted of experimental fishing of drift gillnet in offshore Pelabuhanratu and sampling of skipjack landings at the fishing port.
The gillnets used had a hang-in ratio of 0,4 and mesh size of 4.0, 4.5, 5.0, and 6.0 inches. Each consisted of three pieces that were randomly arranged. The nets were 100 yards in length, 140 meshes in height, and made of nylon multifilament 210D/12.
Factorial design with two treatments, i.e., operation time (Wo) and mesh size (Ms) was used in this research. Two trips of five days fishing operation and five settings in each trip were conducted for the field experiment.
Gonado Somatic Index (GSI) and gonado index (GI) were used as measurement tools for gonad maturity. These indices were needed for determining the optimum mesh size of gillnet.
*Matsuoka, T. 1995. A Method to Calculate Selectivity of Gillnet with a Probability Model Based on Variations of Body Girths. Kagoshima: Faculty of Fisheries, Kagoshima University.