A Morphometric Study on Mahseer (Tor putitora) From a Mid-Hill Lake and Rivers of Nepal

Mahseer or Sahar (Tor putitora, Cyprinidae), one of highly valued, mighty and giant freshwater fish of Transhimalayan regions, is distributed in all major river systems and mid hill lakes of Nepal. It has been hypothesized that differences between habitats (e.g. flow regime, foraging opportunities) might create selective pressures resulting in morphological divergence between intraspecific populations. Morphometric diversifica-tion between three river populations (Koshi, Trishuli, Kali Gandaki) and one lake popula-tion (Phewa lake) of mahseer was examined to identify intraspecific unit for enabling better management and perpetuation of the resources. Morphometric analysis showed that most of the shape variation among these populations occurs in the head region, body depth and fin length. Lake population of mahseer was found to diverge most from river populations. The characters that best discriminated the river and lake population of mahseer were associated with locomotion patterns and foraging behavior of fish. The mahseer may be phenotypically plastic in response to the environmental conditions of the habitat of each population.