Survival and growth rates of wels catfish (Siluris glanis Linnaeus, 1758) larvae originating from fertilization with cryopreserved or fresh sperm

Survival and growth of wels catfish (Silurus glanis L. 1758) larvae (both non-feeding and feeding), originating from fertilization with cryopreserved sperm were investigated. Non-feeding (yolk sac) larvae (n=100 individuals distributed over five replicates) were tested in the laboratory; feeding larvae (100 individuals in five replicates) were tested in both the laboratory and at a commercial fish farm (1000 individuals in triplicates). Water temperature was maintained at 22-23 degrees C during the 4-day test period on non-feeding larvae and 10days on feeding larvae. Larvae originated from cryopreserved or fresh sperm of different males collected in different years. In the laboratory experiments with feeding larvae, changes in standard length (SL), weight, condition factor, specific growth and survival rates were determined after 10days, while at the fish farm survival and length growth were determined after 10days. Final SL, weight and survival rate were analyzed on the non-feeding larvae. In all cases, larvae from fertilization with fresh sperm served as a control. A significant difference (P=0.034) was found in the 10-day standard length between larvae originating from cryopreserved sperm (1.92 +/- 0.13cm SL, N=250) and the control (1.89 +/- 0.14cm SL, N=250). Significant differences were also observed in the final SL (0.96 +/- 0.05cm in larvae from cryopreserved sperm vs 0.94 +/- 0.05cm in the control, P<0.001) and weight (10.09 +/- 0.37g in the cryopreserved group vs. 9.02 +/- 0.30g in the control, P=0.018) of non-feeding larvae. No significant differences were found in either the survival rates of fry derived from fresh or from cryopreserved sperm. It is postulated that the observed differences can be attributed to the effect of individual males or broodstocks; however, genetic studies are required to confirm this hypothesis. This study gives evidence that the developed cryopreservation technology has no unfavorable effects on the viability of wels catfish larvae.