Infection with Dactylogyrus spp. among introduced cyprinid fishes and their geographical distribution in Iran

In the present study, we reported infection with eighteen species of the genus Dactylogyrus, belong to the family Dactylogyridae from five breeder fish species, including common carp (Cyprinus carpio), grass carp (Clenopharyngodon idella), silver carp (Hypophthalmichthys molitrix), big head carp (Hypophthalmichthys nobilis) and black carp (Myelopharyngodon piceus) which introduced and imported to Iranian freshwaters from Russia, Romania, Hungary and China over the last 40 years. The infection was also found in Carassius auratus gibelio, it is not known when this fish species was introduced into the country. The Dactylogyrus spp. were as follows: Dactylogyrus achmerovi, D. anchoratus, D. aristichthys, D. baueri, D. dulikeity, D. ctenopharyngodonis, D. extensus, D. hypophthalmichthys, D. intermedius, D. intermedioides, D. lamellalus, D. magnihamotus, D. nobilis, D. sahuensis, D. suchengtaii, D. taihuensis, D. vastator and D. wegeneri. Among these, D. vastator and D. anchoratus infecting common carp and D. lamellatus infecting grass carp are very harmful and were responsible for high mortalities observed in fry and fingerling production in Iran. Uncontrolled import of live fish into the country can lead to transmission of pathogenic monogeneans or other group of parasites to native fishes, causing a great economical and ecological threat to valuable native fishes. For example, transmission of D. anchoratus from common carp to Barbus sharpeyi, an important native fish species, despite of the high host-specificity of monogeneans, indicates the possibility of transmission of exotic monogenean parasites to native hosts. It. is strongly suggested that the risk of introducing exotic pathogens along with importing fish or any other living organism to the country, should be assessed well in advance, in order to protect native species and the ecosystem.