Size Structure and Biological Aspects of Yellowfin Tuna (Thunnus Albacares) in the Makassar Strait, Indonesia

Abstract

Yellowfin tuna (Thunnus albacares) is a valuable food fish commodity and a main fishery target in West Sulawesi Province, Indonesia. However, the large number of juvenile yellowfin tuna caught by purse seiners, which have shifted from small pelagic fish towards large pelagic fish, could threaten yellowfin tuna populations and thus the sustainability of the fishery. The aim of this research was to analyse size structure and biological aspects of yellowfin tuna caught in the Makassar Strait (by hand line and purse seine fishers) and landed in Majene and Polewali Mandar regencies, West Sulawesi. Yellowfin tuna (N = 2,391) were collected twice a week from August to November 2022 in each regency from intermediate traders; samples were selected randomly. Fork length (FL) and weight were recorded. Gonad maturity level was determined based on gonad morphology. The size range was 11-164 cm, mean ± SD = 60.5 ± 33.9 cm). The length-weight relationship was W = 0.00002*FL2.9461 for male yellowfin tuna and W = 0.00004*FL2.8449 for females, with an isometric growth pattern for both sexes. Condition factor was 14.94 for males and 15.00 for females with a size at first maturity of 106.4 cm for males and 96.8 cm for females. The study results show that many juvenile yellowfin tuna are caught, length and weight increase proportionally, yellowfin tuna were in good condition, and females matured earlier than males.