Fertilization and hatching rate of African catfish eggs using milt from fresh gonads and preserved gonads

Abstract

The African catfish, Clarias gariepinus is one of the most important freshwater fish species currently being cultured both within and outside its natural range of tropical and subtropical environments. In the wild, African catfish has a discontinuous annual reproductive cycle and the breeding season correlates with periods of maximal rainfall. Outside this range of breeding seasons, the availability of high-quality brood stock is scarce therefore to obtain spermatozoa, sacrificing male brood fish by removing the testes is necessary. Sexually matured males were selected and kept in a different tank for about 18 hours before the time of gonad extraction, the testes were perforated with a needle, semen was gently squeezed out, and then stripping off the induced female brood stock was carried out, eggs were mixed with the milt from gonads preserved for 12 h and 24h hand mixture was stirred for 1-2 min to allow contact between the eggs and the spermatozoa. The data collected was subjected to Two-way ANOVA analysis where the number of hatched larvae as a percentage of total eggs exposed to spermatozoa was calculated 24 h after fertilization. The results indicated that the milt obtained from fresh gonads performed better than the preserved milt. The gonads to be preserved should be carefully removed from the male catfish and not damaged. It was observed from this study that the milt could be contaminated by microorganisms during the process of fertilization and therefore, all activities during the process of short-term preservation should be conducted in a sterile environment.