Quantifying habitat overlaps between native and non-native fishes in the Himalayas using MaxEnt models optimized for data-deficient stream networks

Abstract

Fish invasions threaten freshwater ecosystems worldwide, yet methods to map biodiversity in data-deficient regions are scarce. Two salmonids, rainbow trout (Oncorhynchus mykiss) and brown trout (Salmo trutta fario) have been introduced to the Himalayan ecoregion where they are sympatric with vulnerable native snow trout Schizothorax plagiostomus and Schizothorax richardsonii. Our study aims to evaluate potential habitat overlaps between snow trout and non-native trout in the Indus and Ganges River basins, Himalayan ecoregion. We transferred MaxEnt models optimized for data-deficient stream networks to model distribution of potentially suitable streams for rainbow and brown trout in the Himalayas. We adopted a similar procedure to map suitable habitats for snow trout species. We found a substantial overlap (up to 96%) in suitable stream between snow trout and non-native trout. However, physiography of receiving basins could allow minimizing the impacts of each non-native trout on native snow trout. We generate high-resolution classified stream suitability maps as decision support tools to help managers in habitat allocation and policy formation to balance recreational fisheries with conservation of snow trout. Our workflow for optimized MaxEnt models can be transferred to other basins and species for mapping freshwater biodiversity patterns in species-rich yet data-poor regions of the world.