Diseases caused by parasites in the aquaculture of warm water fish

Abstract

Parasitic infections of fish cultured in fresh and marine waters of subtropical and tropical geographic regions are reviewed. The following parasites are discussed: Ectoparasitic protozoa, Coccidia, Myxosporea, Monogenea, Metacercariae of trematodes, the Asian tapeworm, nematodes, ergasilids, lernaeids, and argulids. Criteria for selection were their impact on farmed fish and the availability of data beyond case reports and surveys. Epizootic ectoparasitic infections are usually the outcome of adverse growth conditions, either climatic or resulting from management practices. Epizootiology of infections by internal parasites, heteroxenous in particular, is more complex, particularly in man-made systems, as it is determined by a wider range of interacting ecological parameters. Exotic species, particularly cyprinids, comprise the bulk of freshwater fish farmed in warm water systems. Most important diseases affecting fishes in such systems are caused by introduced pathogens. Only a few of the autochthonous parasites become involved in epizootic infections, also where indigenous species are farmed. Marine farming is usually based on indigenous species. The relatively short history of piscine mariculture has already recorded epizootic infections and mortalities both by parasites contracted from the local environment and by specific parasites associated with the cultured species. As in freshwater systems, culture practices often create an environment favorable to epizootic infection.