Endogenous feeding period of rainbow trout, Oncorhynchus mykiss (Walbaum), in the raceway ponds of Kathmandu, Nepal

Abstract

Endogenous feeding period of 22 months old rainbow trout, Oncorhynchus mykiss (Walbaum), was recorded in the farmers’ raceway ponds. The conversion and change of zygotes to alevins and from alevins to free swimming fries during developmental process and growth were less releasing small-sized alevins and free swimming fries because of the small-sized eggs and small age and size of the broods. Total incubation period was 30 days in water temperature of 9.1-13.1 °C. Hence, incubation period was 25 days in water temperature of 10.89 ± 0.21 °C day-1 and cumulative water temperature (sum total of water temperature of 25 days) of 272 °C with hatching of alevins (survivability 41.82 ± 3.16%), each 0.0365 ± 0.0016 g and 1.46 ± 0.086 cm with 0.0136 ±0.0012 g yolk-sac. Therefore, endogenous feeding period was 5 days in water temperature of 9.1 °C liberating free swimming fries (survivability 76.92 ± 4.91%), each 0.025 ± 0.0007 g and 1.65 ± 0.083 cm ready for the exogenous feeding period.