The decent catch size of mackerel tuna (Euthynnus affinis Cantor, 1849) and its implication to fisheries management in the border area of Indonesia and Timor Leste

Abstract

A study of mackerel tuna (Euthynnus affinis) has been conducted in Ombai Strait in the border area of Indonesia and Timor Leste. The objective of this study is to determine the decent catch size of mackerel tuna in Ombai Strait, based on the length at first caught (Lc), the length of first mature (Lm), and prediction of spawning season. Monthly data collection conducted in May 2018 – June 2019 from fish landing sites in Belu, East Nusa Tenggara, Indonesia. There were 1516 fish collected to measure the total length and gonadal maturity level. The results showed that the size of the mackerel tuna population in the Ombai Strait was between 131 - 450 mmTL. The length at first matured is 210,9 mmTL and the average length at first caught (Lc50) is 152,1 mmTL. Length of first matured was larger than length at first caught (Lm > Lc). The decent catch size is 211 mmTL and the prediction of spawning season in May – June. These results indicate that it is necessary to regulate selective fishing gears to ensure the sustainability of mackerel tuna resources in Ombai Strait.