Quality of African Carp Larvae, Labeo parvus Boulenger, 1902 (Pisces: Cyprinidae) obtained in captivity by hormonal induction of the ovulation.

Abstract

The aim of this study was to evaluate the resistance and quality of Labeo parvus larvae obtained in captivity by artificial reproduction. The larvae used derive from a stock of larvae obtained by hormonal induction of the ovulation using Ovaprim (0.6 mL kg-1 body weight). Larval quality expressed as the time at total mortality and median survival was examined in all crosses under the conditions of osmotic shock (2% NaCl, 26.3°C temperature, 4.4 mg L-1 dissolved oxygen, 8.0 pH) and prolonged fasting (25.2°C temperature, 6.5 mg L-1 dissolved oxygen, 7.6 pH). Osmotic shock and fasting test were conducted using 30 larvae (9 days old) and 30 embryos, respectively at hatching in two replications per cross. Under stress tests no survival was observed after 30 min for osmotic shock and after 16 days for the prolonged fasting test in L. parvus larvae. The median survivals (TL50) were 26.5 min for osmotic shock and 12.5 days for prolonged fasting. There was a statistically significant difference between the median survival of the group exposed for osmotic shock and that the group exposed for prolonged fasting test (p<0.05). These results show a great resistance of the larvae to the osmotic shock and prolonged fasting.