Fish raised in aquaculture ponds may get infected with fishborne zoonotic trematodes (FZT) during the nursing stage. Freshwater snails serve as intermediate hosts for FZT and we wanted to explore the possibility of controlling snails by stocking nursery ponds with a few juvenile specimens of the mollusc-eating fish, black carp (Mylopharyngodon piceus). Obviously, the risk that black carp might also prey on the juvenile fishes in nursery ponds should first be assessed. Laboratory trials showed that all size classes of juvenile black carp consumed fry of common carp (Cyprinus carpio) even when offered snails as food; the odds of survival of fry from tanks with medium sized and large black carp was 5.6% and 39.9%, respectively of that of fry in tanks with small sized black carp. Since the large black carp also consumed fewer snails than medium sized fish, we believe that large specimens were stressed in the experimental aquaria. Under semi-field conditions, presence of the black carp had no effect on survival of fry of Oreochromis niloticus and C. carpio both in the absence and presence of snails as alternative food. The black carp consumed most snails offered with the exception of some of the large snails. We conclude that under field conditions, predation by black carp on fish fry is minimal and field trials in nursery ponds are warranted. Due to the risks that black carp pose to native imperiled snails and other molluscs, trials should be restricted to ponds within the fish's native or existing range.
All Science Journal Classification (ASJC) codes
- Agronomy and Crop Science
- Insect Science