Department of Fisheries , Faculty of Natural Resources, University of Guilan, Somehe Sara 1144,
The fishery of bony fishes has an economic important in southern part of Caspian Sea ,but there are few reports about the pathogens of them in this area .Eustrongylides excisus , a parasite (Nematoda: Dioctophymidae) can damage the muscles of bony fishes . So, consumers avoid to buy the infected fish. Hence , the parasite can cause economic loss.In order to determine the occurance and intensity of the parasite, a survey has been carried out on twelve fish species (no=373) including Cyprinus carpio (no=42), Esox lucius (no=60) , Carassius auratus gibelio (no=42), Abramis brama orientalis (no=50) , Perca fluviatilis (no=36), Vimba vimba persa (no=50) , Chalcalburnus chalcoides (no=50), Barbus capito (no=5) , Aspius aspius (no=5),Neogobius fluviatilis(no=14) , N.kessleri (no=12) and N.caspius(no=7). Common parasitology procedures were used for necropsy of the fishes and recovery of the parasite . Standard statistical computations (mean , Standard Deviation, range, prevalence and dominance) were calculated for the overall samples. Eustrongylides excisus(L) was isolated from Esox lucius (prevalence=5% , mean intensity = 5.33) and P. fluviatilis (prevalence= 33.3% , mean intensity= 1.5) . The parasite was observed as coiled in cysts inside the muscles of these two fish species. The parasite was also isolated from the body cavity of Barbus capito , Aspius aspius and muscles, ovaries, body cavity , upon liver and testis of Neogobius fluviatilis , N.kessleri and N.caspius. The infection of Barbus capito , Aspius aspius, Neogobius fluviatilis , N.kessleri , N.caspius and perch (P. fluviatilis) is reported for the first time from Iran.