ARS | Publication request: RECENT INCIDENTS OF ALGAL TOXICOSIS IN CHANNEL CATFISH (ICTALURUS PUNCTATUS).

Submitted to: American Fishery Society (Fish Health Section) Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: September 6, 2000
Publication Date: September 6, 2000
Citation: SNYDER, S.G., FREEMAN, D.W., GOODWIN, A.E. RECENT INCIDENTS OF ALGAL TOXICOSIS IN CHANNEL CATFISH (ICTALURUS PUNCTATUS).. AMERICAN FISHERY SOCIETY (FISH HEALTH SECTION) PROCEEDINGS. 2000. p.45.

Technical Abstract: Farmers producing channel catfish in ponds with relatively high salt levels (3-5 ppt) report fewer problems with infectious disease and off flavor than do farmers growing fish in fresh water. Unfortunately, these high salt farms experience sporadic unexplained fish kills with varying degrees of mortality. Investigations of these catastrophic fish kills have identified no involvement of infectious diseases or traditional water quality problems. The high mortality and time course of the problem are indicative of exposure to a toxin. Occurrence of the fish kills is associated with heavy blooms of blue green algae especially, Anacystis marina, a halophylic species. Investigation of the involvement of algae in these outbreaks has included exposing channel catfish fingerlings to suspect blooms in bucket bioassays, gavaging, and intraperitoneal injections. Toxicity assays performed with collected pond water and concentrated algae resulted in no deaths for two cases, and 100% mortality in the third case. A microcystin ELISA assay of water from the third case revealed microcystin levels were above 1000 parts per billion. The results of the case studies and ELISA assays demonstrate that algal toxicosis does occur in aquaculture. Channel catfish fingerlings (15 20g) were intraperitoneally injected with microcystin-LR and anatoxin-a. Microcystin levels were measured in bile, liver, and edible flesh of moribund fish by microcystin ELISA assays from EnviroLogix. Protein phosphatase inhibition was measured in liver and edible flesh samples by Serine/Threonine protein phosphatase assay kit. Microscopic analysis of pond water samples was used to determine the dominant algal species in each pond. There was a seasonal correlation between the presence of Anacystis marina and fish kills.