Determination of the appropriate mesh size of drift gillnet for Skipjack tuna (Katsuwonus pelamis (Linnaeus, 1758)) by indirect method

One of the methods of standardization of gill nets is to determine the appropriate mesh size for each species. The purpose of this study was to determine. This study was aimed to determine the suitable mesh size of drift gillnets for catching skipjack (Katsuwonus pelamis).The sampling operation was carried out by the lange boat in the spring of 1397. The fishing tool consisted of drift gillnet for Skipjack tuna with a stretched mesh size of 160 mm. Fork length and body length were measured in two areas of skipjack tuna body. The total numbers of 394 specimens were measured, the fork length range was 38 to 77 cm with mean and standard deviation of 55.02 55 ± 5.90 cm. The highest frequency of Skipjack was in the range of 48-58 cm with 77%. The equations of linear relations between fork length and gill circumference: Gop = 0.577 FL + 1.866 with coefficient of determination 0.926 and linear relation for fork length and body circumference Gmax = 0.922 FL – 9.750 with a Coefficient of Determination 0.963 were gained. The elongation rate was 17% for gill circumference and 21% for the body circumference. In general, based on the present study, a drift gillnet with a mesh size of 136 mm can be used to capture Skipjack, which is slightly smaller than the minimum mesh size used by fishermen.