Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

When nature decides who stays and who goes: priority effects extirpating the non-native brown trout Salmo trutta fario L. population from a Himalayan river.

Abstract

This paper describes the extirpation of the non-native brown trout Salmo trutta fario L. population from a Himalayan river. River Asiganga in Uttarakhand, India was chosen as a case study to understand this theory, where cloudburst-induced flash floods are considered to be a reason for the complete wipe-out of non-native brown trout (Salmo trutta fario), leaving behind the native snow trout (Schizothorax species). A major cloudburst on 3 August 2012 led to a massive flash flood, which unexpectedly changed the flow regime and habitat structure of the river. Surveys were conducted from June 2017 to June 2018 at 14 points along the river, with an interval of 500 m from downstream to upstream starting at Gangori. The average catch per unit effort (CPUE) from a catch containing only the snow trout was 1.75 kg h-1, ranging between 0.22 and 6.14 kg h-1, while no individual of brown trout was encountered throughout the year. Results showed that the 2012 flash flood was the undoubted reason for extirpation of brown trout population from Asiganga.