Evaluation of mercury in rainbow trout collected from Duck Valley Indian Reservation reservoirs, southwestern Idaho and northern Nevada, 2007, 2009, and 2013
The U.S. Geological Survey, in cooperation with the Shoshone-Paiute Tribes of the Duck Valley Indian Reservation, analyzed mercury (Hg) concentration in rainbow trout (Oncorhynchus mykiss) collected from three reservoirs on the reservation (Mountain View, Lake Billy Shaw, and Sheep Creek) during sampling events in 2007, 2009, and 2013, to determine the risk of Hg exposure to Tribal members and the general public.
Mercury concentration in predatory fish tends to increase with fish length, and this tendency was true for rainbow trout in the reservoirs on the reservation (r2 = 0.44–0.70). Mean (average) and median Hg concentrations in fish tissue were determined for each reservoir for each sample year. All Hg concentrations were less than the U.S. Environmental Protection Agency’s water-quality criterion of 0.30 milligram per kilogram (mg/kg wet weight [ww]) and the Idaho Department of Environmental Quality’s reasonable potential to exceed threshold of 0.24 mg/kg. Idaho Department of Health and Welfare toxicologists determined that the Hg concentrations in rainbow trout in this study would not warrant a fish-consumption advisory for this species.
Throughout this report, statistical findings with a p-value of less than 0.05 are referred to as “significant.” Mean Hg concentrations in fish-tissue samples collected from Mountain View Reservoir were higher in 2007 (0.12 mg/kg ww) than in 2009 and 2013 (0.07 and 0.06 mg/kg ww, respectively), indicating a significant mean decrease. Mean Hg concentrations in fish-tissue samples collected from Lake Billy Shaw showed no significant differences among sample years (2007, 0.12 mg/kg ww; 2009, 0.07 mg/kg ww; 2013, 0.09 mg/kg ww). Mean Hg concentrations in fish-tissue samples collected from Sheep Creek Reservoir significantly increased in 2013 (0.10 mg/kg ww) from concentrations in 2007 and 2009 (0.06 and 0.05 mg/kg ww, respectively). These temporal and spatial variations are not unexpected, as each body of water may differ in the factors and conditions affecting the rate of methylation and demethylation.
Coupled with the dynamic put-and-take fishery, the outcomes reflect the system complexities among reservoirs despite their fairly close proximity to one another. The influence of these other factors is evident when the analysis of atmospheric Hg deposition at Mercury Deposition Network site NV02 in northern Nevada showed no significant linear trend in wet Hg deposition rates for 2003–2013 (average 3.02 micrograms per square meter).
Williams, M.L., MacCoy, D.E., and Maret, T.R., 2015, Evaluation of mercury in rainbow trout collected from Duck Valley Indian Reservation reservoirs, southwestern Idaho and northern Nevada, 2007, 2009, and 2013: U.S. Geological Survey Scientific Investigations Report 2015–5079, 18 p., http://dx.doi.org/10.3133/sir20155079.
ISSN: 2328-0328 (online)
Table of Contents
- Data Quality Objectives
- Sampling and Analysis
- Results and Discussion
- References Cited
Additional publication details
|Publication Subtype||USGS Numbered Series|
|Title||Evaluation of mercury in rainbow trout collected from Duck Valley Indian Reservation reservoirs, southwestern Idaho and northern Nevada, 2007, 2009, and 2013|
|Series title||Scientific Investigations Report|
|Publisher||U.S. Geological Survey|
|Publisher location||Reston, VA|
|Contributing office(s)||Idaho Water Science Center|
|Description||iv, 18 p.|
|Other Geospatial||Duck Valley Indian Reservation Reservoirs|
|Online Only (Y/N)||Y|
|Additional Online Files (Y/N)||N|