INFLUENCE OF TEMPERATURE ON EGG HATCHING, GROWTH AND SURVIVAL OF
HETEROBRANCHUS LONGIFILIS VAL. 1840 (TELEOSTEI: CLARIIDAE)
F. M. Nwosu, S. Holzlöhner-2000
Journal of Applied Ichthyology, 16 (1): 20-23
Abstract:
Eggs of Heterobranchus longifilis Val. 1840 were artificially fertilized and incubated at a range of temperatures (20, 23, 25, 27, 29 and 32 degrees C). The time from fertilization to hatching decreased with increasing temperature. No eggs survived to hatch at 20 and 32 degrees C incubation temperatures, while at 23 and 29 degrees C hatching was only minimal. Optimum hatching was obtained at 25 and 27 degrees C, which corresponds to the ambient temperature range during the breeding season. Larvae of H. longifilis were reared for 11 days post-hatching at 20, 25, 27, 29 and 32 degrees C. Growth increased with temperature (P < 0.05), whereas survival depicted an inverse relationship. Growth was minimal at 20 degrees C and larvae rarely survived to the end of the experiment. Optimum temperature for the primary nursing of H. longifilis larvae was within the 25-27 degrees C temperature range.
(Institute of Oceanography, University of Calabar, Calabar, Nigeria)