Synergistic effects of thyroxine and feeding regimes on early survival and biomass gain in Asian catfish, magur (Clarias batrachus, Linn.) larvae

Abstract

The larvae of catfish, Clarias batrachus (av. wt. 15 ± 2 mg) were exposed to five concentrations of thyroxine (T4) with three feeding regimes. Five media 1.3 mcg L−1 (T-1), 2.2 mcg L−1 (T-2), 3.6 mcg L−1 (T-3), 6.0 mcg L−1 (T-4), 10.0 mcg L−1 (T-5) of T4 and control with three feeding regimes 1 day (once a day), 2 days (twice a day) and 3 days (thrice a day) were maintained in triplicate set in 54, troughs containing 2-L water. The larvae reared in media (T1, T2, T-3, T-4 & T-5) with feeding regimes 1 day, 2 days & 3 days showed 100 % survival which was significantly high (p < 0.05) in comparison to control (60.5 ± 0.7, 64.5 ± 0.7 and 71.0 ± 1.4 % respectively with regimes 1 day, 2 days and 3 days). Net gain in biomass was found significantly higher (p < 0.05) in feeding regimes 3 days (C, 244.7 %; T-1, 305.7 %; T-2, 217.5 %; T-3, 369.9 %; T-4, 371.4 %; T-5, 298.3 %) and 2 days (C, 146.5 %; T-1, 186.6 %; T-2, 122.7 %; T-3, 243.6 %, T-4, 200 %, T5, 123.4 %) in comparison to 1 day. The synergistic effects of T4, feeding regimes and their interaction evaluated through two-way ANOVA. The color of the fish-body was more darker in the case of experimental fishes in comparison to the control groups. The findings suggest that thyroxine enriched ambient water and feeding regimes had a significant role in improved survival and growth on C. batrachus larvae, a prioritized fish for aquaculture.