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

Abstract

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

ACKNOWLEDGMENTS

We thank Neil Mochnacz (Department of Fisheries and Oceans, Winnipeg, Manitoba); Mark Gillespie and Craig McDougall (North-South Consulting, Winnipeg); Jon Tsetso, Ashley Okrainec, Aaron Donohue, and Marcel Cholo (Nahanni National Park Reserve, Fort Simpson, NWT); and Scott Semple (Great Slave Helicopters, Fort Simpson) for assistance with field work. Thanks to Morag McPherson (Department of Fisheries and Oceans, Yellowknife, NWT) for reviewing the manuscript and providing support for our analysis and reporting efforts. Funding for the project was provided by Parks Canada Agency (Nahanni National Park Reserve, National Office), Canadian Zinc Corporation, NWT Cumulative Impact Monitoring Program, and Fisheries and Oceans Canada’s Federal Contaminated Sites Action Plan. Comments from two anonymous reviewers improved several aspects of our manuscript and shaped our interpretation of the relevance of nonlethal methodologies.