A Pcr‐based Test to Assess the Potential for Microcystin Occurrence in Channel Catfish Production Ponds1,2

Microcystis aeruginosa is a common form of cyanobacteria (blue‐green algae) capable of forming toxic heptapeptides (microcystins) that can cause illness or death. Occasionally, blooms of cyanobacteria have caused toxic fish‐kills in catfish production ponds. We have developed a PCR test that will detect the presence of microcystin‐producing cyanobacteria. Microcystin producers are detected by the presence of the microcystin peptide synthetase B gene (an obligate enzyme in the microcystin pathway), which appears to be present only in toxin‐producing cyanobacteria. These PCR amplifications can be performed in multiplex using purified DNA from pond waters or by two‐stage amplification from native water samples. A synoptic survey of 476 channel catfish production ponds from four states in the southeastern United States revealed that 31% of the ponds have the genetic potential to produce microcystins by toxic algae.