Can the Sri Lankan endemic-endangered fish Labeo fisheri (Teleostei: Cyprinidae) adapt to a new habitat?

Abstract

Labeo fisheri is an endemic and endangered freshwater fish of Sri Lanka. Mainly restricted to the upper reaches of the Mahaweli River basin, it has been previously reported living in deep rapids and among large rocks and boulders. An accidental record of a Labeo fisheri specimen from Victoria Reservoir led us to further study this habitat during the period from January to August 2017. This study was carried out to confirm the presence of a population of Labeo fisheri within the Victoria Reservoir and report its new habitat type in deep stagnant waters. We further investigated the food habits by analyzing the gut contents of L. fisheri in the Victoria Reservoir. Seven individuals were recorded from fishermen’s gill net catch in three fish landing sites along Victoria Reservoir, with an average total length of 24.80 ± 4.30 cm, average standard length of 19.70 ± 3.86 cm and average body weight of 197.69 ± 107.12 g. Based on gut content analysis, only phytoplankton, especially diatoms and cyanobacteria, were found in the gut of L. fisheri. This new population is facing the direct threat of fishing. Effective conservation measures are doubtful, since a fishery is well established in the Victoria Reservoir and the fishing gear used is not species-specific. More research is necessary to understand the population dynamics of L. fisheri in the Victoria Reservoir. In order to conserve it at this locality, community-based conservation measures are recommended.