The influence of age on the occurrence of internal parasites in perch (Perca fluviatilis L.) from Lake Góreckie in Wielkopolski National Park

The European perch (Perca fluviatilis L.) is a common freshwater fish which is widely distributed in Europe and Asia and has been successfully introduced to New Zealand and Australia. It is the intermediate and definitive host of many parasites, especially endoparasites, such as trematodes, cestodes and nematodes (Bikhovskaya-Pavlovskaya and Kulakova,1987; Carney and Dick, 1999; Behrmann-Godel and Brinker, 2005; Wierzbicka et al., 2005; Kuchta et al., 2009). Information concerning the parasites of perch can be found in widely published literature (Rolbiecki, 2006; Halmetoja et al., 2000), but still little is known about aspects such as the age dynamics of infections with endoparasites. Parasites provide a great deal of biological information about their host, regarding migration, differences in diet, and food web structure (Williams et al., 1992; MacKenzie et al., 1995; Marcogliese et al., 2006). On the other hand, parasitism may influence the behaviour of fish (hosts), resulting in changes in their habitat and increasing vulnerability to predators (Seppälä et al., 2008). Infection with parasites increases the relative risk of mortality in the host (Behrmann-Godel and Brinker, 2005). In this paper we determined the occurrence of parasites in perch from Lake Góreckie, Wielkopolski National Park. Perch is common in water bodies and has a diverse diet, and for these reasons it is the definitive or intermediate host of many parasite species. Therefore, this fish species was selected for our study. The influence of age on the occurrence of parasites in perch has not yet been examined in detail. The aim of this study was to answer the following questions: • What parasites occur in perch in Lake Góreckie? • Which species of endoparasites are more frequently observed in perch in Lake Góreckie? • Is there a correlation between the occurrence of the endoparasite and the age of perch?