Assessment of reproductive potential and spawning patterns of <i>Barilius bendelisis</i> (Hamilton, 1807) in tributaries of the Ganga River in the Garhwal Himalayan region

Understanding reproductive strategies is essential for the biological conservation and management of hill-stream fishes in dynamic freshwater ecosystems. The present study investigated the reproductive biology of Barilius bendelisis (Hamilton, 1807), a key cyprinid species inhabiting three different streams and tributaries of the Ganga River viz.: the Song River, Sahastradhara, and Henval River in the Garhwal Himalayan region. The study was conducted from September 2023 to May 2025, covering all major seasons. Key reproductive parameters, including sex ratio, gonadosomatic index (GSI), Dobriyal index (DI), fecundity, and sexual dimorphism, were examined to determine spawning periodicity and reproductive potential. A female-biased sex ratio was consistently observed across all sites, with overall sex ratios of 1:1.14, 1:1.1, and 1:1.45 in the Song, Sahastradhara, and Henval Rivers, respectively. Peak GSI and DI values were recorded during the summer and monsoon seasons, indicating these seasons as the primary spawning period, with DI showing greater precision in identifying spawning periods. Fecundity varied among sites and showed a strong positive correlation with gonad weight, reflecting site-specific reproductive investment. Notably, males displayed prominent breeding tubercles during the spawning phase, serving as markers for sexual dimorphism. Overall, the findings reveal spatial variation in reproductive traits and highlight adaptive strategies of B. bendelisis in Himalayan hill-stream ecosystems. These insights offer a scientific foundation for developing season-specific conservation strategies, regulating fishing pressure during peak breeding periods, promoting the sustainable management of freshwater biodiversity in the Garhwal Himalayas. Keywords: Conservation, Dobriyal index, Fecundity, Gonadosomatic index, Hill-stream ecosystems, Indian hill trout, Sexual dimorphism