TWENTY-FOURTH ANNUAL EASTERN FISH HEALTH WORKSHOP Royal Pavilion Resort, Atlantic Beach, NC MARCH 9-11, 1999 Massive Lernaea Infestations Damaging The Gills Of Channel Catfish (Ictalurus punctatus) Polycultured With Bighead Carp (Hypophthalmichthys nobilis) Andrew E. Goodwin Aquaculture/Fisheries Center, University of Arkansas Pine Bluff, 1200 N. University Dr., P.O. Box 4912, Pine Bluff, AR 71611 Fish farmers in the southeastern United States are now polyculturing bighead carp (Hypophthalmichthys nobilis) with channel catfish (Ictalurus punctatus). Bighead carp are filter feeders that are very efficient at capturing the large zooplankters that are plentiful in nutrient-rich intensive catfish production ponds. Bigheads have become popular because they increase farm income without adding to feed costs. Unfortunately, as the number of farms raising bigheads has increased, it has become evident that there are risks in polyculturing these two species. In June and July of 1998, there were three occurrences of major catfish losses in commercial production ponds where catfish were polycultured with bighead carp. Bighead carp harvested from the ponds had hundreds of adult Lernaea on their skins. Moribund catfish in the same ponds had only a few Lernaea along the bases of medial fins but were found to have from 8-50 immature Lernaea (copepodids) on the surface of each gill filament. The copepodid Lernaea greatly resembled other predacious cyclopoid copepods and were clearly feeding on catfish gill tissue. Their feeding activity was associated with gill damage including epithelial hyperplasia, telangiectasis, and hemorrhage. All moribund catfish from the three cases had many Lernaea copepodids on their gills. No other parasites or diseases were found. Interestingly, although bighead carp in these ponds had numerous adult Lernaea on their skins, no carp died during the epizootics. It is possible that copepodids entering the mouths of bigheads were collected by the filter feeding apparatus of the carp and consumed, and thus did not have access to the gill filaments. Catfish mortality in two of the three cases described peaked within a few days of harvesting a large percentage of the bigheads from the polyculture ponds. Bighead carp in sufficient numbers may keep copepodid densities low enough to protect catfish from heavy infestation. Lernaea copepodids have not been previously implicated in fish losses due to gill damage and losses of channel catfish to Lernaea infestations have not been reported. It seems likely that, in the cases reported here, the catfish were killed by the copepodid progeny of adult Lernaea living on bighead carp. Return to 24th Annual Eastern Fish Health Workshop Return to Leetown Science Center Home Page