Snow trout in Nepal

A.K. Rai, B.R. Pradhan, S.R. Basnet

Snow trout, a cold water riverine and short migratory fish is locally known as asla. It belongs to the family Cyprinidae and sub-family Schizothoracinae which are widely distributed in the Himalayan and sub-Himalayan region and much of the rest of Asia. Altogether 28 species of snow trout are reported of which 6 species of genus Schizothorax and 3 species of genus Schizothoraichthys are recorded in Nepal. Schizothoraichthys progastus (altitude distribution 300-1 820 m), locally called Chuche asla, and Schizothorax plagiostomus (altitude 345-3 323 m), called Buche asla, are high value sport fish and are common in Nepal. Asla is a phytophagous fish and has developed a special mouth to scrape the algae attached on stones. Asla spawn twice a year during September/October and March/April, but September/October is the best season for spawning. Clear water, stony bottom of creeks composed of fine pebbles and gravel, and water flow of 2.8-4 m/sec, pH 7.5 and dissolved oxygen concentrations of 10-15 mg/L form good spawning conditions in the natural environment. Asla has been bred artificially in the Fisheries Research Centre Trishuli since 1971 but the hatching rate is low and mortality of alevins is still high (>50%). Fully mature females release orange and sticky eggs when gently pressed on the abdomen but it requires a very specific time for spawning to get good quality of eggs.

Asla brood fish maintained in concrete raceway ponds and fed 35% protein content diet at 1-2% of body weight produce about 12 000 eggs/kg. Hatching takes place within about 11 days at water temperature 15-20°C and Buche asla is easier to breed than Chuche Asla. The development from one- day hatchling to free swimming stage varies inversely with temperature, ranging from 5 days at 24°C to 24 days at 12°C, and the survival rate is higher (>90%) at 20-24°C, lower (65%) at 17°C and [ Continue reading at http://www.fao.org/docrep/005/y3994e/y39… ]