Objective: To study the prevalence and mean Intensity of Eustrongylides excisus (L) in different bony fishes and compare the infection between these species.
Design: Descriptive study.
Animals: 373 samples of twelve different fish species of Caspian Sea and its basin (Anzali wetland) including Cyprinus carpio
(no=42), Esox lucius (no=60) , Carassius auralus gibelio (no=42), : Abramis brama orienialis (no=50), Perca fluviatilis (no=36), Vimba
vimba persa (no=5O), Chalcalburnus chalcoides (no=50), Barbus capito (no=5), Aspius aspius (no=5), Neogobius fluviatilis(no=l4),
N.kessleri (no=12) and N.caspius (no=7) were examined from september 1999 to september 2001.
Procedure: Cutting the wall of body cavity and removing viscera including intestine, liver, ovaries, testis and etc to isolate the parasite. Cutting the muscles and finding the cysts of the parasite in them. Fixing the larvae by ethanol 70%, clearing by lactophenol and identifying them by identification keys (Moravec, 1994).
Statistical analysis: Prevalence rate mean intensity ± standard deviation.
Results: Eustrongylides excisus (L) was isolated from Esox lucius (prevalence5%. mean intensity= 5.33) and P. fluviatilis
(Prevalence= 33.3%, mean lntensity= 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 upon liver and testis of Neogobius fluviatilis (prevalence=35.7%,
mean intensity= 8.4), N.kessleri (prevalence=50%, mean intensity =10.8) and N.caspius (prevalence=14.3%, mean intensity= 1).
Conclusion: In this survey, the diversity of fish species infected
with Eustrongylides excisus (L) was high, but in spite of the
diversity, the Intensity and abundance of the parasite were low both in marine and freshwater fishes .The prevalence of the parasite in
marine and migratory fishes was more than freshwater fishes. The infection of Barbus capito, Aspius aspius, Neogobius fluvialilisN.kessleri, N.caspius and perch (P. fluviatilis) is reported for the ,first time from Iran. J. Fac. Vet. Med Univ. Tehran. 57, 1: 37-41, 2002.