Intra‐annual changes in reproductive indices of male and female Himalayan snow trout,Schizothorax richardsonii(Gray, 1832)

Abstract

Periodic changes in reproductive hormone levels, gonadal histology and gonadosomatic index (GSI) of snow trout, Schizothorax richardsonii, were examined to ascertain annual cycle of gonadal development and reproductive status in their natural habitat. In females, there were coherent changes in plasma 17β‐oestradiol and vitellogenin along with GSI, oocyte maturation and vitellogenic progression, collectively indicating two distinct maturation peaks during the months of September and February. Coinciding with this, in males, plasma 11‐keto testosterone was also noticeably higher during September and February, with highest GSI values in September. However, plasma 17α, 20β‐dihydroxyprogesterone levels in males were found to be persistently high from September to February. This observation suggests the potential presence of matured oozing males over a longer period, unlike in females. Overall, the close association between reproductive hormone levels, GSI and gonadal maturation stages in males and females (particularly, the presence of postovulatory follicle complexes) with apparent natural synchronization clearly indicates that S. richardsonii breeds twice in a year, possibly during late September to early November and late February to early April in the coldwater riverine habitats of the Indian Himalayan region.

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

“…This aligns with previous studies, confirming biannual spawning in the Indian Himalayan region. Our GSI findings closely resembles with findings of Joshi et al (2016) and Ciji et al (2021), with a peak in September-October and a low in November-December, consistent with earlier reports by Abuzinadah (2001), Wagle (2014), and Joshi et al (2016).…”

Ecological Adaptations and Conservation Challenges of Schizothoracids in High Altitude Environments: A Mini Review

“…Schizothorax labiatus, another snow trout species in Kashmir, has also been studied for its reproductive and breeding biology, contributing to its conservation and management (Farooq et al, 2019). In addition, studies on male and female Himalayan snow trout, Schizothorax richardsonii (Ciji et al, 2020), have investigated intra-annual changes in reproductive indices to understand sex steroid hormone profiles and gonadal histology variations. These studies provide a holistic understanding of the unique characteristics and adaptations of these fishes to high-altitude environments.…”

A study on the seasonal cyclicity of ovarian development in adult Himalayan snow trout, Schizothorax plagiostomus

“…Numerous reports are available on the oocyte maturation and ovarian development in freshwater teleosts (Basu et al ., 2004; Chaube et al ., 2022; Malison et al ., 1994; Shein et al ., 2004; Singh et al ., 2008). Nonetheless, limited studies have been undertaken till date to understand the ovarian cyclicity of Cyprinidae fishes (Hliwa et al ., 2017; Manorama & Ramanujam, 2017; Sivakumaran et al ., 2003), including Schizothoracine species like Schizothorax richardsonii (Agarwal et al ., 2004; Bisht & Joshi, 1975; Ciji et al ., 2021; Joshi et al ., 2016), Schizothorax labiatus (Arafat & Bakhtiyar, 2022; FAROOQ et al ., 2018; Farooq et al ., 2019), Schizothorax niger (Hussain et al ., 2018; Malhotra, 1970; Sabha et al ., 2017), Schizothorax curvifrons (Qadri et al ., 2019; Sunder, 1984), Schizothorax plagiostomus (Agarwal & Singh, 1991; Arif et al ., 2019; Jan & Ahmed, 2019; Pasha et al ., 2016; Shrestha & Khanna, 1979; Singh et al ., 2016). Furthermore, the nomenclature and terminology used for identifying the ovarian developmental stages/maturational phases in teleost fishes by various authors are overlapping, and thus remain indistinct and confusing (Agarwal et al ., 2004; Agarwal & Singh, 1991; Arafat & Bakhtiyar, 2022; Arif et al ., 2019; Bisht & Joshi, 1975; Ciji et al ., 2021; FAROOQ et al ., 2018; Farooq et al ., 2019; Hliwa et al ., 2017; Hussain et al ., 2018; Jan & Ahmed, 2019; Joshi et al ., 2016; Malhotra, 1970; Manorama & Ramanujam, 2017; Pasha et al ., 2016; Qadri et al ., 2019; Sabha et al ., 2017; Shrestha & Khanna, 1979; Singh et al ., 2016; Sivakumaran et al ., 2003; Sunder, 1984).…”