Tehran University of Medical Sciences Iranian Journal of Parasitology 1735-7020 6 3 2011 09 15 66 73 EN J Pazooki Department of Marine Biology, Faculty of Biological Sciences, Shahid Beheshti University, G. C., Tehran, Iran F Tajbakhsh Goorabzarmakhi Department of Marine Biology, Faculty of Biological Sciences, Shahid Beheshti University, G. C., Tehran, Iran M Masoumian Department of Fish Diseases, Iranian Fisheries Research and Training Organization, Tehran, Iran 2015 10 03 Background: In Anzali Lagoon, there are some endemic and exotic fishes. The present study was conducted to compare the parasitic fauna of Blicca bjeorkna, as an endemic fish and Hemicul­ter leucisculus, as an introduced fish to the lagoon. Methods: A parasitological investigation was done on 78 specimens of B. bjoerkna and 114 of H. leu­cisculus. The fishes were collected from August 2009 to April 2010 by the electro fishing from Anzali Lagoon. Results: Eleven parasites species were found in 192 fish samples. The prevalence and mean inten­sity of parasites in each host were as follows: Parasites from B. bjorkna were  Trichodina perforata (53.85%); Myxobolus musayevi (27.19%, 1±0.79); Dactylogyrus difformis (88.05%, 8±7.24) and D. sphyrna (5.18%, 0.95±0.51), Diplostomum spataceum (98.72%, 9.51±9.01), Post­hodiplostomum cuticula (15.38%, 4.25±2.5), Ripidocotyle sp. (1.28%, 2±0.74); Contracaecum osculatum (17.95%, 1.64±0.79), Philometra rischta (12.8%, 1.4±0.54), and Raphidascaris acus (1.04%, 0.03±0.26). The H. leucisculus were infected with T. perforata (27.19%), D. spataceum (7.89%, 1.33±0.54), Ps. tomentosa (7.02%, 1.62±0.49) and R. acus (0.88%, 3±0.28). B. bjoerkna was presented as a new host for M. musayevi and C. osculatum, while H. leucisculus was intro­duced as a new host for T. perforata and Ps. tomentosa. Conclusion: The prevalence of parasites was significantly more in native fish than that of exotic fish (P<0.05). This reduction in parasitic infection in H. leucisculus may be due to its immune system resistance, well adaptation to the new environment, host-specific limitation for endemic parasites and disability of introduced parasite to complete its life cycle in the new host as well. https://ijpa.tums.ac.ir/index.php/ijpa/article/view/190 https://ijpa.tums.ac.ir/index.php/ijpa/article/download/190/189