Biological Characteristics of Bigeye Thresher Shark (Alopias superciliosus) Landed in Cilacap Ocean Fishing Port, Cilacap Regency, Central Java, Indonesia

Shark is the top predator of the marine food chain which has a unique biological condition, namely a long life cycle and is prone to population decline in nature if its utilization is not carried out wisely. This study aims to analyze the biological conditions of bigeye thresher shark (Alopias superciliosus) which includes sex ratio, length at first capture (Lc), length-weight relationship, condition factor, sexual maturity and length at first maturity (Lm) in male sharks during March-June 2023 landed at Cilacap Ocean Fishing Port. The results of the analysis of the sex ratio of female and male bigeye thresher sharks were 1:1.74, indicating that the sex ratio of female and male sharks is not balanced. The length at first capture (Lc) of female, male and combined sharks were 145.38 cmFL, 148.12 cmFL and 148.79 cmFL, respectively. Length-weight relationships of female, male and combined bigeye thresher sharks showed an isometric growth pattern. Condition factor values of the length-weight relationship equation ranged from 0,82-3,07. The level of sexual maturity of bigeye thresher shark was classified as 14,5% NC category, 19,7% NFC category, and 65,8% FC category, indicating that most were in the ready to spawn category. The length at first maturity (Lm) in male sharks was 145,97 cmFL. The sharks caught are mostly mature in size, so the utilization of bigeye thresher shark requires catch quotas and size restrictions as well as monitoring of shark fishing areas, which are indispensable in bigeye thresher shark conservation management efforts.