Some Biological Parameters of Yellowfin Tuna (Thunnus albacares) from the Handline Fishery in the Eastern Part of the Banda Sea

Abstract

Export quality yellowfin tuna (Thunnus albacares) from the handline fishery in the Banda Sea (Ambon and Seram) is vital in supporting coastal communities. To ensure its sustainability, information on their biological parameters is essential, especially for harvest strategy purposes. A combination of port sampling and fisheries surveys were conducted from January to October 2016 to monitor the catch, effort, size (length and weight), and maturity level of yellowfin tuna. An equal catch proportion of yellowfin and bigeye tuna was found during surveys in Masohi, Seram Island. In contrast, two-thirds of the catch landed in Ambon was dominated by yellowfin tuna. The catch rate varied between 25.5-71.9 kg/day. Length of samples distributed between 65-152 cm FL (mode=104 cm FL), whereas estimated live weight ranged from 6.12-148.92 kg. Both females (W=0.000001∗FL3.7190) and males (W=0.000001∗FL3.7438) possessed allometric growth. The proportion of males was twice that of females (1: 0.5), where most (47%) of samples were found to be mature. The estimated total mortality (Z) is 1.04/year, with the natural mortality (M) and fishing mortality (F) is around 0.55/year and 0.49/year, respectively. The stock condition allegedly reaching its optimum level tagged by the length at first caught (Lc) was slightly higher in comparasion to length at first maturity (Lm50 ) and utilization rate (E) below 0.55/year.