The potential impacts of climate change on response and interaction of native and non native trout populations in selected riverscapes of Indian Himalayan region

Abstract

This thesis is an effort to understand the multifarious responses of native snow trout to the pressures posed by brown trout invasion and climate change in Himalaya. With no research available for scientifically-backed conservation and management of native species in invaded Himalayan riverscapes, the study is specifically targeted to support policy decisions. By considering snow trout in Asiganga watershed as a natural control representative of an allopatric association with brown trout, the impacts of invasion on sympatric snow trout in Tirthan and Parwati watersheds were made explicit. With a progression from spatial competition to life history responses of altered phenology, reproduction and growth, the study settles with a holistic understanding on the future of natives and their interactions with invasives under climate change. The results indicate fast life-history adaptations of the natives under invasion. As the invasion and climate change stressors tend to act in synchrony, responses of snow trout under invasion hint on its plausible resilience to climate change. Nonetheless, the species distribution modelling preformed in this study hints at an overall high-altitude squeeze for the natives, with predicted increase in the area of native-invasive overlaps. Furthermore, the spatial stream network models and the field observations made during this study indicate an invasion-induced relegation of native snow trout from favourable sites of rest and forage. Overall, the stressors under climate change and invasion indicate a detrimental impact on natives, given, the brown trout propagule pressure is continued by the local angling associations and fisheries departments across Himalayan watersheds. newline