Population sizes of metazoan parasites of brook trout (Salvelinus fontinalis) and Atlantic salmon (Salmo salar) in a small Newfoundland lake

Abstract

The metazoan parasite community of fishes (Salvelinus fontinalis, Salmo salar, Gasterosteus aculeatus) in a small lake in central Newfoundland, Canada, was studied. It consisted of three components: parasites of salmonids (Salmincola spp., Discocotyle sagittata, Apophallus imperator, Diplostomum sp., Tetracotyle sp. 1, Cystidicoloides tenuissima, Eubothrium salvelini, Diphyllobothrium sp., glochidia), parasites of sticklebacks (Gyrodactylus avalonia, Tetracotyle sp. 2, Shistocephalus solidus), and parasites shared by salmonids and sticklebacks (Ergasilus sp., Metechinorhynchus lateralis, Crepidostomum farionis). Population estimates were made of the salmonid fishes by the Schnabel mark–recapture method. By multiplying infection prevalence × intensity × number of fish, population estimates were obtained for each species of salmonid parasite. This information revealed that S. fontinalis carries almost all of the salmonid parasite populations and that the seaward migration of S. salar at 2–5 years of age is an insignificant loss to the parasite community. It also revealed that the majority of the population of C. tenuissima, M. lateralis, and Ergasilus sp. is carried by the more abundant small fishes, while the majority of the population of D. sagittata, A. imperator, Tetracotyle sp. 1, and S. edwardsii is carried by the less abundant large hosts. Possible reasons for these two distributions are discussed.