15 MARCH 1999
SALINITY INFLUENCE ON THE EARLY STAGES OF THE AFRICAN CATFISH
A.J. Gbulubo, E.S. Erondu-1998
Aquaculture International, 6 (5) : 369-377 (Current Contents)
Abstract:
Experiments were conducted to determine the effect of various incubation salinities on the hatching and survival of eggs and hatched fry respectively of the African catfish (Clarias gariepinus). The optimal salinity for the hatching of the eggs ranged from 0-5 ppt. Above 5 ppt, hatching was significantly low and no hatching occurred at 8 ppt incubation salinity. Median lethal times (LT50) for fry hatched in 0, 2 and 4 ppt incubation salinities, when abruptly transferred to 10 ppt were 59, 49.5 and 50 h respectively. Similarly, LT50 for fry hatched in 0, 2 and 4 ppt incubation salinities, and abruptly transferred to 12 ppt salinity were 17, 22 and 12.50 h respectively. Increase in incubation salinity of the eggs did not seem to enhance the salinity tolerance of the hatched fry.The gradual (stepwise) increase in salinity of 1 ppt per day of the catfish fry hatched in various incubation salinities (0, 1, 2, 3, 4, 5 and 6 ppt) had median lethal salinity values of 8, 8, 8, 10, 10, 11 and 11 ppt respectively.
(Univ Port Harcourt, Inst Agr Res & Dev, Port Harcourt, Nigeria)