Abstract

Too many male catfish are sacrificed to obtain enough milt for fertilizing fish eggs. The wastage of these fish gametes during breeding due to seasonality and limitations of milt collection make it compelling to explore preservative measures for sperm storage. This study was carried out to evaluate milt characteristics and the effect of different extenders on the sperm of wild African catfish; Clarias gariepinus (C. gariepinus) in Maiduguri, Nigeria. The effects of preservation of C. gariepinus milt at 4℃ and at -196℃ was also investigated. Forty wild male C. gariepinus brood stock from Lake Alau, Maiduguri were used. The brood stocks were sacrificed, dissected and their reproductive tracts exposed and isolated. The testes were identified, stripped and milt samples collected, pooled and their pre-extension characteristics evaluated. Four different semen extenders; OviPlus® + egg yolk (E1), OviPlus® + coconut milk (E2), OviPlus® + coconut milk + egg yolk (E3) and coconut milk-based (E4) were used to extend and preserve the milt through chilling (4℃) and freezing (-196℃) for 4 and 2 days, respectively. The characteristics of extended, chilled and frozen milt were evaluated. The result of the study showed that E1, E2 and E3 maintained the sperm progressive motility up to 48 hours post extension (≥50%) and E4 maintained the progressive motility for up to 72 hours (>50%) at 4℃. All extenders used maintained progressive motility (>50%) and livability (>60%) post-thawed after freezing at -196℃. Conclusively, E4 showed better milt qualities preserved at 4℃ and -196℃. Thus, wild C. gariepinus milt can be collected and extended in coconut milk based extender and used to fertilize C. gariepinus eggs or preserved short-term at 4℃ or frozen at -196℃.

Key words: Chilled storage, Clarias gariepinus, Coconut milk, Cryopreservation, Milt