Thirty three Gyrodactylus spp have been found on the gills and body surface of both wild and farmed freshwater fishes in Iran. Among them nine species have been identified up to the species level, which are new locality records. The identification of the others, mainly belong to endemic wild freshwater fishes, need further studies. Among the known species, Gyrodactylus derjavini (Mikhailov, 1975) has been found on the gills, caudal and anal fins of the Caspian salmon (Salmo trutta caspius) and rainbow trout (Oncorhynchus mykiss). These species are very harmful to salmonid fingerling production industry of Iran. In warm water cultured fishes, G. sprostona, with widest host range, infects common carp (Cyprinus carpio), Silver carp (Hypophthalmichthys molitrix) and big head carp (Aristichthys nobilis) in almost all fish farms of Iran. Other species, which will be discussed here from their economic importance and host specificity points of view, are G. cyprini, G, elegans, G, fossilis, G. kobayashii, G. prostae, G. shulmani and G. stankovici. Furthermore the pathogenecity of Gyrodactylus spp are discussed and new technology (DNA sequence) for precise identification of parasites is also recommended.
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