Captive-Bred Snow Trout Face High Mortality After Release in Uttarakhand Lakes

Scientists from Kumaun University released roughly 350 lab-bred snow trout fingerlings into a cage in Naini lake on April 27, 2026, as part of a captive-breeding programme to revive the vulnerable Himalayan fish. Locally known as Asela, the native cold-water species has been listed as Vulnerable on the IUCN Red List since 2010 and was considered locally extinct for thirty years. Using Biofloc and recirculating aquaculture system technology, researchers bred the fish across two phases before expanding the initiative in June to Bhimtal, Sattal, and Naukuchiatal lakes with smaller cages.

High Mortality

Programme staff report that more than half of the fingerlings have died in Naini lake, with similar high mortality rates in Bhimtal. Vishal Singh of CEDAR describes Naini lake as being on a ventilator, noting it has relied on 30 aerator pipes since 2007 due to critically low oxygen levels. Harpinder Veer Singh Randhawa of Global Aqua Treatment Technology states that a pipe burst in 2019 and the aeration system needs an overhaul, but funding and approval for replacement pipes presented a year ago remain pending. Meanwhile, Harish Chandra Bisht, who heads the breeding programme at Kumaun University, maintains that conditions have improved and trout can adapt, noting they plan to release the fish into open water in October after six months in cages.

Environmental Threats

Experts note that snow trout require clean, well-oxygenated water between 8°C and 22°C, but Naini lake surface temperatures now regularly climb above 25°C in summer, reaching a maximum of 27°C this July according to Ashutosh Mishra. Mishra also questions the local extinction claim, stating he has previously seen trout in the lake, and adds that the species naturally prefers flowing snow-fed rivers rather than still lakes. Additional pressures include competition from the exotic common carp introduced during the British era, drying recharge sources, and construction around Sukhtal lake that disrupts Naini lake's natural drainage.

Context

Cold-water Himalayan fish species are increasingly vulnerable as rising regional temperatures and heavy pollution alter fragile lake ecosystems. Conservation efforts face steep hurdles when the natural habitats required for a species to feed, breed, and survive are heavily degraded by human activity and climate shifts.