FISHERIES RESEARCH INSTITUTE,MOA,TAIWAN

Skipjack tuna (Katsuwonus pelamis) is a tropical species that has been historically exploited off the coast of Taitung (eastern Taiwan). The objective of this study will be used as biological input parameters for stock assessment and management strategy evaluation, furthermore to sustainable resource utilization. Samples were collected monthly from the Shinkang fish market of Taitung from January to December 2020. A total of 358 individual samples were collected (fork length ranged between 31.0 and 74.5 cm, and round weights ranged from 0.5 to 8.7 kg). The sex ratio for monthly and total samples was generally 1:1. The monthly female gonadosomatic index ranged from 0.50 to 2.46 and peaked from April to June, whereas the monthly male GSI ranged from 0.12 to 2.28 and peaked from May to July. According to histological observations of gonad variations, the greatest proportion of mature females was collected from March to August and peaked from April to July. The estimated 50% length-at-maturity (Lm50) was 51.5 cm for females and 53.4 cm for males.