Growth Pattern, Gonadal Maturity, Condition Factor and Gill Net Selectivity of the Hard-Lipped Barb (Osteochilus hasselti CV) from Sungai Batang River, Indonesia

This study examined the growth pattern, condition factor (K), length at first capture (Lc50), length at first maturity (Lm50), gonadosomatic index (GSI), and selection factor (SF) of the hard-lipped barb (Osteochilus hasselti CV) in Sungai Batang River, Indonesia. Fish were weekly purchased from local fishermen over a two-month period (April-May 2024). A total of 355 specimens were studied, consisting of 204 males and 151 females, with total lengths ranging from 60 to 190mm and weights from 2 to 91g. The fish exhibited an isometric growth (b = 2.98–3.04) and were in good condition, with a sex ratio of 1.4:1. The length-weight relationship was strongly positive (r = 0.9575–0.9863). No significant differences were observed in total length (TL), body weight (W), or the mean W/TL ratio between the sexes. However, females had higher mean values for body depth (BD), BD/TL ratio, and K value compared to males. The Lc50 was greater than the Lm50, indicating a high likelihood of spawning. The Lc50 and SF values were 116.5mm and 3.65, respectively, suggesting that the use of a 1.25-inch mesh size gillnet is suitable for fishing practices. A follow-up collection of fish samples was conducted three months later (June-August 2024) to investigate the maturity stages of both sexes and determine their GSI. Macroscopic morphological characteristics revealed that testes could be classified into four stages: immature, mature, ripe/spawning, and spent. Female ovaries were classified into five stages: immature, mature, ripe, spawning, and spent. The GSI values for males ranged from 1% to 10.52%, while those for females ranged from 1% to 13.46%. The findings of this study provide a valuable baseline for evidence-based fisheries management.