Aphanizomenon flos-aquae,A Toxic Blue-Green Alga in Commercial Channel Catfish,Ictalurus punctatus,Ponds: |
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| Abstract: | During the summers of 1990 and 1991 in the Lowcountry region of South Carolina, high mortality rates (50-90%) of channel catfish, Ictalurus punctatus, in production ponds were attributed to the toxic form of the blue-green alga (Cyanobacterium) Aphanizomenon flos-aquae. Toxicity varied with algal strain and/or stage in life history, and a simple bioassay was developed to account for the differential toxicity of algae within ponds. The bioassay required an intraperitoneal injection of a sonicated, 30X concentrate of algal cells that are injected into 8- to 20-g fish. Injection with 0.05 ml of concentrate from the toxic strains caused hyperactivity and paralysis in fish within 10 minutes and mortality within an hour. The endotoxin from A. flos-aquae (aphantoxin) was neutralized with the equivalent of 1.7 mg/L potassium permanganate beyond demand. In production ponds, an application of copper sulfate followed with potassium permanganate had variable success. Muddying the ponds had only limited success but appeared promising. Water and soil chemistry in this geographic area probably influenced the frequency of toxic A. flos-aquae blooms. |
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