EFFECT OF LIGHT PERIODICITY AND INTENSITY ON THE GROWTH AND SURVIVAL OF HETEROBRANCHUS LONGIFILIS VAL. 1840 (TELEOSTEI: CLARIIDAE) LARVAE AFTER 14 DAYS OF REARING
F. M. Nwosu, S. Holzlöhner-2000
Journal of Applied Ichthyology, 16 (1): 24-26
Abstract:
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.
(Institute of Oceanography, University of Calabar, Calabar, Nigeria)