METAZOAN PARASITE COMMUNITIES OF YELLOW EELS (ANGUILLA-ROSTRATA) IN ACIDIC AND LIMED RIVERS OF NOVA-SCOTIA

Metazoan parasite communities of 269 yellow eels (Anguilla rostrata) inhabiting acidic (pH 4.5-5.0) and deacidified (limed to a pH of 6.0-7.0) portions of a watershed in southwest Nova Scotia were compared over 3 years. Paraquimperia tenerrima, Ergasilus celestis, Bothriocephalus claviceps, Proteocephalus macrocephalus, Crepidostomum brevivitellum, and Azygia longa were found. Species richness was greater and there were more multiple infections in the component community in eels from the limed portion of the watershed than in the community in the acidic river. Differential susceptibility of the parasites or their intermediate hosts to acidification appears to be involved in structuring the community. Digeneans were absent from eels in the acidic river. The copepod E. celestis occurred throughout the watershed but was less common in the acidic river. The occurrences of two species, B. claviceps, and P. macrocephalus, were similar at acidified and limed sites. Numbers of infected fish and prevalence of the dominant parasite, P. tenerrima, were highly variable in eels from the acidic region, but were relatively stable at the limed site. It is concluded that the assemblage of metazoan parasites of fish may be useful as environmental indicators, and may also provide information on the dynamics of altered food webs.