The present study aims to assess the epidemiology of fish parasites in culturedfish populations. This study was carried out during a three year period (2005)(2006)(2007) at a tench (Tinca tinca L.) fish farm located in the Northwestern region of Spain. 114 fish as well as 14 physicochemical and microbiological water parameters were analyzed in order to determine the main impact of both the host and the environmental parameters on the presence and the abundance of parasites in their host

more »

... rasite relation).Four different parasites, namely Ichthyophthirius multifiliis, Tripartiella sp., Myxobolus sp. and Gyrodactylus sp., were isolated, being the ciliates, with up to 100% of prevalence, the most abundant, with only 5.56% and 2.63% of the fish infected by the myxozoan and the monogenean, respectively. With the exception of the high alkalinity registered at the fish farm (pH > 9.0), the rest of the values fell within the recommended water quality parameters for cyprinids. The statistical and epidemiological analysis revealed that size, somatic condition and sex (intrinsic parameters) in addition to several environmental factors, linked to seasonality and poor water quality, have significant effect on the host-parasite relationship, increasing the likelihood of the parasite presence (p<0.050). We conclude that, in temperate climates, the development, reproduction and transmission of the parasites are triggered under the most stable conditions of the ecosystem (hydrological, physicochemical and biological) i.e. the warmer periods of the year, when the cyprinid populations display a more active and gregarious behavior. The results of the present study will also help understanding both the epidemiology and the parasitology of fresh water cultured-fish, and, what is more important, will help designing management strategies and procedures for preventing parasitic diseases