Importance of lake characteristics in structuring parasite communities of salmonids from insular Newfoundland

Abstract

Metazoan parasites of Salmo salar and Salvelinus fontinalis were studied at eight sites in insular Newfoundland. The locations included water bodies of various sizes (<1, 1–100, and >100 ha) and depths (<1, 1–5, and >5 m). Nine of 14 parasite species were salmonid specialists and generally had wider geographic distributions than the remaining generalists, with one exception (Echinorhynchus lateralis). The distributions of Crepidostomum farionis, Sterliadochona ephemeridarum, and E. lateralis appeared to be facilitated by the widespread distribution of intermediate hosts. Larval digeneans (Apophallus imperator, Diplostomum sp., and Tetracotyle sp.) were typically associated with shallow medium-sized lakes. Species using limnetic copepods as intermediate hosts (Philonema agubernaculum, Eubothrium salvelini, and Diphyllobothrium sp.) were most often found in fishes inhabiting the deeper lakes. Small ponds had low parasite richness (R = 5); medium and large lakes had similar richness (R = 9–11). Jaccard's index and cluster analysis revealed that fishes in the small ponds and deep lakes had inherently different parasites from fishes of the shallow medium-sized lakes, the latter containing fishes parasitized by larval digeneans. Based on the study it was concluded that lake depth is a fundamental factor determining the structure of parasite communities in salmonids in insular Newfoundland.