Potential use of certain parasites of brook charr (Salvelinus fontinalis) as biological indicators in the Tabusintac River, New Brunswick, Canada
A survey of 1146 nonanadromous and anadromous brook charr (Salvelinus fontinalis) from the Tabusintac River for parasites revealed 36 species of parasites, of which 18 were freshwater and 18 were marine. Most freshwater parasites were either too common or too rare in their occurrence to be of any value as biological indicators; however, Diplostomum sp. (metacercariae), Truttaedacnitis truttae, and Salmincola edwardsii were useful as indicators of foci of infection in fresh water. Decreases in prevalences of infection with marine gastrointestinal parasites in the estuary, especially Brachyphallus crenatus, Neoechinorhynchus sp., and larvae of Hysterothylacium aduncum, provided evidence for the approximate times of arrival of anadromous charr from fresh water. Marine gastrointestinal parasites were also useful as biological indicators of anadromous charr in fresh water, but these parasites were lost after varying times. High prevalences of infection with metacercariae of the marine digenean Cryptocotyle lingua resulted in a black spot condition that proved to be the best indicator of anadromous charr in fresh water. The distributions of Azygia longa, Echinorhynchus lateralis, and Zoogonus lasius from charr in the Tabusintac River as well as the nearby Miramichi and Burnt Church estuaries suggested that estuarine wanderings among adjacent river systems do occur. Tetraphyllidea gen. sp. plerocercoids from anadromous charr in the Tabusintac River were useful in identifying offshore movements of these charr into the Gulf of St. Lawrence.