Gill net selectivity, length at first capture and length at first gonad maturity on Hampala macrolepidota (Kuhl & Van Hasselt, 1823) in Ranau Lake, Indonesia

Hampala macrolepidota is one of the dominant species was caught in Ranau Lake, (name of city/province). This species has an economic value because its highly demand in the community around the lake. The objective of this study was to know the gill net selectivity, lenght at first capture (L_c) and length at first gonad maturity (L_m) of Hampala macrolepidota, in Ranau Lake. This study was carried out in March to November 2013. Samples of fish were obtained using an experimental fishing in two stations, Banding Agung and Talang Teluk. Fishing gear used two different mesh sizes, 1.5 and 1.75 inches, respectively. For length at first capture and size at first gonad maturity, 11/2, 13/4, and 21/2 inch-mesh sizes were employed. Results showed that optimum length of fish caught was 16.154 cm and 18.846 cm in 11/2 and 13/4 inch mesh size, respectively. The selective size ranged from 9.5-19.6 cm and 12.5-22.1 cm, respectively. L_c/L_50% was 15.2 cm, 18.3 cm and 26.8 cm for 11/2 13/4 and 21/2 inch mesh size, respectively. L_m was 15.38 cm for males and 19.21 cm for females, respectively. Among fishing gear selectivities, L_c/L_50% and L_m had very strong relationship, in which compared with L_m value, female hampala population is very alarming since 11/2 and 13/4 inch mesh sizes caught immature gonad females. Good mesh size used was 21/2 inch, due to catching post-spawning-sized hampala. Fishing immature fish could cause fish resources extinction.