Toxic Algae, Fish Kills and Fish Disease

Abstract

Toxin-producing algae are becoming an increasingly serious worldwide problem in both aquaculture and fisheries populations. They affect the gamut of aquatic taxa, from marine mammals to finfish to shellfish. The prevalence of toxic algae blooms appears to be dramatically increasing worldwide and in addition, the magnitude (i.e., severity) of the blooms appears to be increasing. New types of toxic algae as well as algae which were never before known to produce toxins are also being reported. While acute mortalities (eg., kills) due to toxic algae have been the focus of attention for some time, there is now evidence that exposure of aquatic animals to toxin-producing algae can lead to serious sublethal effects, including predisposing these populations to various infectious diseases. These findings indicate that the potential impacts of noxious algae blooms may extend well beyond our traditional concepts of risk from toxic algae exposure and may play as yet undefined but crucial roles in the health of both natural and cultured aquatic populations. One specific toxic dinoflagellate, Pfiesteria piscicida, is used to illustrate this point.