Effect of light periodicity and intensity on the growth and survival of Heterobranchus longifilis Val. 1840 (Teleostei: Clariidae) larvae after 14 days of rearing

Heterobranchus longifilis Val. 1840 larvae were reared under two light intensities, 30 lux and 915 lux, and at varying photoperiods. Results show that maximum survival (82.5 ± 6.5% respectively) at 30 lux was obtained at continuous illumination [24 h light (L)], while the minimum (65 ± 21.2%) was at the 6 h L : 18 h dark (D) treatment. Survival at 24 h D averaged 71.3 ± 6.3%, with no significant difference (P < 0.05) in growth of larvae. Maximum larval survival at 915 lux was 87.5 ± 17.7% at the 18 h L treatment. Growth was not significantly different (P < 0.05) in the treatments. Comparison of the two light intensities showed that survival was better at a photoperiod above 12 h irrespective of intensity, while growth was significantly better at the 915 lux intensity.