An Investigation of Fin Erosion in Channel Catfish

Abstract

An ongoing case of fin erosion affecting Ictalurid catfishes at an aquaculture research facility in the southeastern United States was investigated. Circumstantial evidence collected at this facility has provided several clues as to the cause of the fin lesions. The appearance of the insult is isolated to a heated and dechlorinated municipal water supply when used for flow-through culture systems. Three species of catfish have been affected while species representing five other families are not affected when exposed to the same conditions. The severity of fin erosion increases with temperature and water exchange rate. A pilot study demonstrated that treatment of the water supply with activated alumina protected channel catfish against fin erosion, while increasing hardness or alkalinity did not. A larger study investigated the possibility that chronic exposure to zinc could cause fin erosion in channel catfish. The results of this study showed that fin erosion occurred but was not significantly influenced by zinc exposure. This study also revealed that blood calcium concentration declines over time under these conditions. The cause of fin erosion at this facility remains unidentified.