Influence of salinity on the development stages of African catfish (Clarias gariepinus)

Abstract

Salinity tolerance was tested in fertilized eggs, yolksad larvae, post yolksac larvae and fingerlings of Clarias gariepimus at 0, 2.5, 5.0, 7.5, 10.0, 12.5 and 15ppt salinity. The highest hatchability was observed in fertilized eggs incubated in 2.5ppt, which recorded 71.8%. This was however not significantly higher than the 66.29% and 65.89% hatchability, recorded for the control group (Oppt) and 5ppt respectively. The median lethal salinity values in 96 hours (MLS-96) obtained for the yollac larvae, post yolksac larvae and fingering stages are; 1.9, 2.2 and 7.8 respectively, demonstrated an ontogenetic variation in salinity tolerance of C. gariepimus. However, salinity tolerance of the fertilized eggs, larvae and fingerlings of C. garlepimus is observed to be generally low, and typically of fresh water stennohaline species. This relatively low salinity tolerance of C. gariepinus has probably prevented its existence in brackish waters. None of these stages are suitable for the transfer of C. gariepimus to brackish water environment for the purpose of commercial fish farming. However, results obtained in this study, could be a guide for the use of salt in the prophylactic and therapeutic control of pathogens sensitive to salt. The salinity tolerance of C. gariepimus is dependent on the developmental stage of the fish