Abstract
Seasonal changes of abiotic factors and their influence on parasite occurrence have repeatedly been studied. Most of the studies have been conducted to evaluate the effect of water physicochemical parameters on changes in the intensity of infection, prevalence and component community of a number of parasite species. However, insufficient attention has been paid to the link between water quality parameters and spatial niche size of ectoparasites. The distribution of ectoparasite species on perch (Perca fluviatilis L.) was studied to establish whether seasonal changes of water quality parameters are associated with ectoparasite spatial niche size. The concentration of phosphates (PO43−), nitrates (NO−3), sulphates (SO42−) and dissolved oxygen (DO) in the water of Lake Sila (Latvia) was measured every month throughout the year and recorded all ectoparasites on perch. Zero-inflated mixed models were used to evaluate which of the water parameters influence the spatial niche size of ectoparasites. Our findings showed that spatial niche size of some ectoparasite species is affected by a set of water quality parameters and that this effect is negative. The spatial niche size of Anodonta cygnea was negatively associated with phosphate, nitrate, sulphate and dissolved oxygen concentration. The spatial niche size of Ancyrocephalus percae was negatively associated with sulphate, and the spatial niche size of Ergasilus sieboldi was negatively associated with nitrate concentration.