Larval survival and growth in Wallago attu (Bloch and Schneider): effects of light, photoperiod and feeding regimes

Abstract

An in-door rearing study was conducted for 11 days with Wallago attu larvae fed on live zooplankton alone (control) or combinations of zooplankton and dry feed containing either fish meal (F1), meat meal (F2) or shrimp meal (F3) under 24 h continuous light (24L), 12 h light–12 h dark (12L:12D), 24 h red light (24RL) or complete darkness (0L). The percent survival of larvae was significantly different ( P<0.05) among the larvae reared under various light regimes with highest in 24RL, followed by 24L, 12L:12D and 0L, in descending order. Fish fed on combination of live plus dry feeds grew significantly faster than those fed on zooplankton alone. There was no significant difference in growth of fish reared under different light and photoperiod regimes when fed on live zooplankton alone. The specific growth rate (SGR) was significantly greater ( P<0.05) in fish fed on the combination of zooplankton and dry feeds as compared to zooplankton alone. At the end of the experiment, total biomass production was the highest ( P<0.05) in larvae reared under the red light and lowest in the 0L treatment. Permanent darkness reduced percent survival and suppressed total biomass production of W. attu larvae. Red light and continuous lights promoted higher survival and biomass production as compared to 12L:12D or 0L regimes. For highest survival and maximum biomass production, 24 h red light exposure is suggested best during in-door rearing of W. attu larvae.