Reproductive Strategy and Dynamics of the Endangered Himalayan Fish Schizothorax richardsonii in Kumaun Himalayan Snow-fed Rivers, Uttarakhand, India

Abstract

Schizothorax richardsonii, an endangered fish in Uttarakhand's Himalayan rivers, is economically and ecologically vital but increasingly vulnerable. Gonadosomatic Index (GSI) reveals spawning biology, while maturity stages indicate reproductive health. The study assessed females (60-780 g, 17-44 cm) and males (52-278 g, 17-26 cm), with GSI ranging from 0.305 to 9.69 and 0.18 to 9.70 in both sexes. Maximum GSI was recorded from August to October (primary breeding) and a slight peak from late February to April (secondary breeding). Six maturity stages were identified which are based on ova morphology and its frequency distribution, including ova diameter (0.6-2.5 mm), ova radius (0.32-1.29 mm), ova area (0.33-4.53 mm²), and ova perimeter (2.09-8.08 mm), observed annually in various months, highlighting sexually dimorphic traits during breeding and challenges in differentiation outside the breeding season. These findings aid in the sustainable management of S. richardsonii in hilly regions.