Investigating the Effect of Water Source on Relative Frequency and Diversity of Cultured Rainbow Trout, Oncorhynchus mykiss (Walbaum, 1792) Ectoparasites in Qazvin Province

A fish species that lives in two different geographical regions may have some minor or evident differences in frequency and diversity of ectoparasites. Physical and chemical differences of water source, presence of intermediate hosts of some parasites and many other complicated factors interfere in this aspect. This research was done during 36 months from 1388 to 1391 in rainbow trout farms of Qazvin province to study the effect of water source in frequency and diversity of ectoparasites of Cultured Rainbow Trout. For this purpose 1150 rainbow trouts with clinical signs from seven farms with will source and average temperature of 15ͦ c and three farms which receive water from river system with average temperature of 11 ͦ c were caught and transferred alive to the laboratory of veterinary medicine department of Qazvin. Parasite experiments were done using the wet smear of skin, and checked with identification key. Results showed that the farms with river system, despite situating one after another, had less frequency and diversity of ectoparasites in comparison with fish which receive water from the will with higher average temperature. The parasites in river-system farms were consist of Trichodina sp. with the most frequency in spring, Ichthyophthirius sp., Gyrodactylus sp., Dactylogyrus sp. and Ichthyobodo sp. with the most ffequency in summer and also Chilodonella sp. with the most frequency in winter. The parasites in will farms were consist of Ichthyophthirius sp.,Trichodina sp.,Gyrodactylus sp., Dactylogyrus sp. , Chilodonella sp., Lernaea sp., Epistylis sp., Tetrahymena sp., Cryptobia sp. and Vorticella sp. from which the most frequent infections were Ichthyophthirius sp. and Tricodina sp. with the most frequency in summer and fall, respectively, and Chilodonella sp. with the most frequency in winter