Quantifying Elements in Arctic Grayling and Bull Trout in the South Nahanni River Watershed, Northwest Territories, Using Nonlethal Tissue Samples

Monitoring of contaminants in fish generally involves lethal sampling, but public scrutiny and increased pressure on fisheries have driven the need to develop nonlethal sampling methods. We examined the ability of adipose, anal, and caudal fin tissues to serve as nonlethal surrogates for lethal muscle tissue samples in the analysis of metals (elements). First, we evaluated the use of biopsies by examining relationships between concentrations of 39 elements in low-volume dorsal muscle biopsies and high-volume muscle samples from Arctic Grayling Thymallus arcticus and Bull Trout Salvelinus confluentus collected in the South Nahanni River watershed, Northwest Territories, Canada. Low-volume dorsal biopsy samples in this study served to most closely model the concentrations of elements found in high-volume dorsal samples; caudal and anal fins were more representative of high-volume dorsal samples than were adipose fins. Regressions between high- and low-volume dorsal muscle samples were significant for 12 elements/species, with Cs, Rb, and Tl having the strongest relationships in both species. Regression analyses comparing low-volume muscle samples and fin samples revealed variation between Arctic Grayling and Bull Trout, but Co, Hg, and Tl concentrations among samples were strongly related for both species. Addition of fish length or age as a covariate did not greatly improve the predictive power of calculated regressions. For future monitoring, selection of a nonlethal sampling strategy (e.g., use of dorsal biopsy or adipose fin samples) will require consideration of the element of interest, the primary route of exposure, interaction with other elements, and the basic biology and ecology of the fish species. Ideally, nonlethal sampling tools can be further developed for the two species to promote inclusion of community partners; these tools offer sustainable, long-term approaches for monitoring sensitive fish populations in northern Canadian habitats.

Received February 29, 2016; accepted September 9, 2016Published online December 20, 2016