U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2015–5079

Prepared in cooperation with the Shoshone-Paiute Tribes of the Duck Valley Indian Reservation

Evaluation of Mercury in Rainbow Trout Collected from Duck 

Valley Indian Reservation Reservoirs, Southwestern Idaho and 

Northern Nevada, 2007, 2009, and 2013

Evaluation of Mercuy in Rainbow Trout 

Collected from Duck Valley Indian 

Reservation Reservoirs, Southwestern 

Idaho and Northern Nevada, 2007, 

2009, and 2013

By Marshall L. Williams, Dorene E. MacCoy, and Terry R. Maret

Prepared in cooperation with the Shoshone-Paiute Tribes of the Duck Valley 

Indian Reservation

Scientific Investigations Report 2015–5079

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2015

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Suggested citation:

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)
iii

Contents

Abstract ..........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Regulatory Guidance............................................................................................................................3

Purpose and Scope ..............................................................................................................................3

Description of Study Area ...................................................................................................................3

Data Quality Objectives.................................................................................................................................3

Sampling and Analysis..................................................................................................................................4

Field Sampling Methods ......................................................................................................................4

Fish-Tissue Laboratory Analysis.........................................................................................................4

Atmospheric Mercury Deposition Data Analysis............................................................................4

Statistical Analysis ...............................................................................................................................5

Results and Discussion.................................................................................................................................6

Rainbow Trout Mercury Concentrations...........................................................................................6

Atmospheric Wet Mercury Deposition .............................................................................................8

Quality Control for Fish Analysis ........................................................................................................8

Summary..........................................................................................................................................................9

Acknowledgments.........................................................................................................................................9

References Cited............................................................................................................................................9

Figures

1. Map showing location of Duck Valley Indian Reservation reservoirs and

Mercury Deposition Network sites (NV02 and NV99), southwestern Idaho and

northern Nevada...........................................................................................................................2

2. Graphs showing mercury concentration in fish tissue by length from Duck Valley

Indian Reservation reservoirs and hatchery background samples from the Black

Canyon Trout Farm, southwestern Idaho and northern Nevada, 2007, 2009, and

2013 .................................................................................................................................................5

3. Boxplots showing sample concentration by year for rainbow trout sampled from

Duck Valley Indian Reservation reservoirs, southwestern Idaho and northern

Nevada, 2007, 2009, and 2013......................................................................................................7

4. Graph showing annual wet mercury deposition rate at Mercury Deposition

Network site NV02, Lesperance Ranch, Nevada, 2003–2013................................................8

Tables

1. Statistical summary of annual sampling events for Duck Valley Indian Reservation 

reservoirs, southwestern Idaho and northern Nevada, 2007, 2009, and 2013 ....................6

2. Individual fish size, weight, and mercury concentration data, and statistical

summaries for Duck Valley Indian Reservation reservoirs and hatchery background 

samples from the Black Canyon Trout Farm, southwestern Idaho and northern 

Nevada, 2007, 2009, and 2013....................................................................................................12

3. Quality-control results for analysis of total mercury in fish from Duck Valley Indian 

Reservation reservoirs and hatchery background samples from the Black Canyon 

Trout Farm, southwestern Idaho and northern Nevada, 2007, 2009, and 2013 .................16
iv

Conversion Factors

Inch/Pound to SI

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

Area

acre 4,047 square meter (m2)

acre 0.004047 square kilometer (km2)

square mile (mi2) 2.590 square kilometer (km2)

Mass

ounce, avoirdupois (oz) 28.35 gram (g)

pound, avoirdupois (lb) 0.4536 kilogram (kg)

SI to Inch/Pound

Multiply By To obtain

Length

centimeter (cm) 0.3937 inch (in.)

millimeter (mm) 0.03937 inch (in.)

kilometer (km) 0.6214 mile (mi)

Mass

milligram (mg) 0.00003527 ounce, avoirdupois (oz)

gram (g) 0.03527 ounce, avoirdupois (oz)

kilogram (kg) 2.205 pound avoirdupois (lb)

Abbreviations

ANOVA analysis of variance

CRM certified reference material

Hg mercury

IDEQ Idaho Department of Environmental Quality

IFCAP Idaho Fish Consumption Advisory Program

IAEA International Atomic Energy Agency

MDN Mercury Deposition Network

MeHg methylmercury

NADP National Atmospheric Deposition Program

QC quality-control

RPTE reasonable potential to exceed

USEPA U.S. Environmental Protection Agency

USGS U.S. Geological Survey

USGS MRL U.S. Geological Survey Mercury Research Laboratory
Evaluation of Mercury in Rainbow Trout Collected from 

Duck Valley Indian Reservation Reservoirs, Southwestern 

Idaho and Northern Nevada, 2007, 2009, and 2013

By Marshall L. Williams, Dorene E. MacCoy, and Terry R. Maret

Abstract 

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). 

Introduction

The Duck Valley Indian Reservation spans the border 

of Idaho and Nevada (fig. 1). The reservation, established by 

executive order on April 16, 1877, is home to about 2,000 

members of the Shoshone-Paiute Tribes (hereafter referred 

to as “the Tribes”). The Tribes manage three reservoirs 

(Mountain View, Lake Billy Shaw, and Sheep Creek 

Reservoirs) on the reservation as a subsistence fishery, and 

sport fishery for recreation and economic benefit. The Tribes 

have expressed concern about the potential for mercury (Hg) 

contamination of these reservoirs and their aquatic biota. 

Research conducted in 2005 by Abbot and others (2008) from 

the U.S. Department of Energy Idaho National Laboratory 

showed elevated levels of atmospheric Hg entering southern 

Idaho from gold processing sites in northern Nevada. Average 

Hg concentrations of trout sampled from nearby Nevada 

waters in 2005 and 2006 were 0.09–0.17 mg/kg ww (Nevada 

Department of Wildlife, 2007). Because of mercury’s potential 

toxicity to humans, the Tribes needed more information 

on the occurrence of Hg concentrations in their fishery 

to help determine if those concentrations posed a risk to 

Tribal members and the general public. To determine the 

bioaccumulation of Hg in the Tribes’ rainbow trout fishery and 

the potential risk to the consumers, the U.S. Geological Survey 

(USGS) began monitoring Hg concentrations in rainbow trout 

in the reservation’s three reservoirs in 2007, with additional 

sampling conducted in the 2009 and 2013.
2 Mercury in Rainbow Trout, Duck Valley Indian Reservation Reservoirs, Southwest Idaho and Northern Nevada, 2007, 2009, and 2013

tac14-0959_fig01

STATE HWY 51

STATE HWY 225

Lake Billy 

Shaw

Sheep Creek

Reservoir

Mountain View

Reservoir

Owyhee

Base map modified from U.S. Geological Survey digital data, 1:100,000. 

Coordinate Reference System IDTM83, Transverse Mercator projection.

Horizontal datum is North American Datum of 1983.

Duck Valley

Reservation

NEVADA

IDAHO

116°18' 116°07'30" 115°57'

42°

10'

42°

00'

41°

50'

0 2.5 5 10 KILOMETERS

0 2.5 5 10 MILES

NV02 NV99

IDAHO

NEVADA

Duck Valley

Reservation

Figure 1. Location of Duck Valley Indian Reservation reservoirs and Mercury Deposition Network sites (NV02 and NV99), 

southwestern Idaho and northern Nevada.

Mercury is a global pollutant that ultimately makes its 

way into every aquatic ecosystem through the hydrologic 

cycle. Atmospheric deposition of inorganic Hg contributes 

the vast majority of Hg to aquatic systems as either dry fall 

or scavenged during precipitation events, although geologic 

sources and point-source pollution also may contribute to 

Hg loading (Rada and others, 1989; Fitzgerald and others, 

1991; Kamman and Engstrom, 2002). Once it is in aquatic 

systems, inorganic Hg may become methylated through 

microbial sulfate and iron reduction (Fitzgerald and Lamborg, 

2003; Fleming and others, 2006; Kerin and others, 2006). 

Reservoirs are particularly prone to Hg methylation because 

of increased microbial activity that results from water-level 

fluctuations; they can also respond quickly to direct Hg 

deposition (Sorensen and others, 2005; Wiener and others, 

2007; Brigham and others, 2014). Methylmercury (MeHg) 

is the more bioavailable and toxic form of Hg; once Hg 

has moved through aquatic food chains into predatory fish, 

almost all Hg present in fish tissue is MeHg. In turn, sport 

fish that are most commonly captured and consumed by 

subsistence or recreational anglers tend to be predatory fish. 
Data Quality Objectives 3

As a result of these dynamics, risks of human exposure 

to MeHg are primarily through consumption of fish 

(U.S. Environmental Protection Agency, 2001). Sources of 

Hg often are not well quantified. However, they likely include 

atmospheric deposition, historical gold mining operations, and 

natural sources. The U.S. Environmental Protection Agency 

(USEPA, 2015) Toxic Release inventory for data from 2001 

to 2013 shows that most Hg (stack) emissions in Nevada 

come from gold mining and processing facilities. Mercury 

often is released from thermal processes where it enters the air 

during the gold extraction process (Jones and Miller, 2005). 

Air emissions from these mining and processing facilities 

may travel great distances, affecting States throughout the 

Intermountain West. In 2001, USEPA toxic release inventory 

data showed that Nevada metal mining companies reported 

releasing about 9 percent of total U.S. mercury compounds 

as point source (stack) emissions. This amount has steadily 

decreased, becoming 6.5 percent of the total U.S. emissions 

in 2002, 3.6 percent in 2003 (Jones and Miller, 2005), and 

1.4 percent in 2013. Overall, reported Hg mass from stack 

emissions attributed to mines and mine processing in Nevada 

has decreased from about 11,800 lb in 2001 to 932 lb in 

2013, a 92 percent decrease (U.S. Environmental Protection 

Agency, 2015).

Regulatory Guidance

The USEPA recommended a water-quality criterion for 

MeHg expressed as a fish-tissue residue value (MeHg in fish 

tissue) of 0.30 mg/kg ww (U.S. Environmental Protection 

Agency, 2001). The MeHg criterion is based on fresh weight, 

appropriately indicating the nature of fish destined for 

human consumption. This criterion is based on protecting 

an adult consumer who eats an average of 17.5 g of fish per 

day, equivalent to about one 8-ounce serving every other 

week (U.S. Environmental Protection Agency, 2001; Idaho 

Department of Environmental Quality, 2005). 

The Idaho Department of Environmental Quality (IDEQ) 

adopted the USEPA fish-tissue criterion and established a 

reasonable potential to exceed (RPTE) threshold designed to 

protect consumers that is 20 percent lower than the criterion 

or Hg greater than 0.24 mg/kg ww based on an average 

concentration of 10 fish from a receiving waterbody (Idaho 

Department of Environmental Quality, 2005). The Idaho Fish 

Consumption Advisory Program (IFCAP) applies an even 

lower action level of 0.22 mg/kg ww Hg, which is compared 

to the geometric mean Hg concentration of 10 fish of a single 

species collected from a single water body (lake or stream). 

IFCAP compares the action level and angling usage of each 

water body to determine if a consumption advisory should 

be issued.

For this study, total Hg is analyzed in place of MeHg 

in fish tissue for two reasons: (1) total Hg is easier and less 

costly for laboratories to determine than MeHg, and (2) nearly 

all Hg present in fish muscle tissue is MeHg (Bloom, 1992; 

Hammerschmidt and others, 1999; Harris and others, 2003). 

In comparing fish-tissue results with the criterion, the 

analytical results for total Hg in the fish tissue should be 

interpreted as 100 percent MeHg. For the remainder of this 

report, total Hg analyzed in fish tissue will be referred to 

as “Hg”.

Purpose and Scope

This report presents the results of the fish tissue analysis 

from samples collected from three reservoirs on the Duck 

Valley Indian Reservation in 2007, 2009, and 2013 in order 

to identify changes in fish-tissue Hg concentration within and 

between reservoirs for different sampling periods. A summary 

of annual atmospheric deposition rates measured at one of two 

northern Nevada Mercury Deposition Network (MDN) sites 

also is included. The scope of the investigation is limited to 

rainbow trout in the range of sizes people are likely to catch 

and eat from the reservoirs on the reservation.

Description of Study Area

Duck Valley Indian Reservation encompasses nearly 

290,000 acres, of which 22,000 acres are wetlands. Three 

reservoirs were created on the reservation as a subsistence 

fishery, but they also provide the Tribes with a valued sport 

fishery for recreation and economic benefit (fig. 1). Mountain 

View Reservoir lies in the north-central part of the reservation 

and is about 2 mi long with a surface area of about 630 acres. 

Lake Billy Shaw is about 9 mi southwest of Mountain View 

Reservoir and covers about 430 surface acres near the central 

area of the reservation. Sheep Creek Reservoir is 6 mi south 

of Lake Billy Shaw in the south-west area of the reservation 

and covers about 855 surface acres. The perimeters of 

the reservoirs are shallow coves with riparian vegetation 

consisting of cattails, willows, and other aquatic vegetation; 

upland areas around the reservoirs primarily are sagebrush 

and grasses.

Data Quality Objectives

Data-quality objectives for sample collection, analysis, 

and reporting for this study are listed as follows, and provide 

Hg concentrations in fish-tissue data collected from Mountain 

View, Lake Billy Shaw, and Sheep Creek Reservoirs:
4 Mercury in Rainbow Trout, Duck Valley Indian Reservation Reservoirs, Southwest Idaho and Northern Nevada, 2007, 2009, and 2013

1. Collect fish that represent the size range (>25 cm) 

likely to be captured and consumed by recreational or 

subsistence anglers near the sampling sites (table 2, at 

back of report).

2. Analyze hatchery trout provided by the Tribes from 

the Black Canyon Trout Farm in Grace, Idaho, as 

background samples for Hg concentration in stocked fish 

(table 2).

3. Use sample processing, handling, storage, shipping, 

and quality-assurance protocols sufficient to avoid 

introducing sample contamination or bias to the data.

4. Use laboratory analytical techniques that have 

sufficiently low detection limits to quantify Hg 

concentrations in fish tissue at less than 0.24 mg/kg ww 

(Idaho RPTE threshold). 

5. Analyze quality-control samples to provide accuracy 

and precision information for the fish-tissue samples 

collected (table 3, at back of report). Quality control 

included analysis of certified reference material (CRM) 

to verify instrument calibration (accuracy), and analyses 

of triplicate fish-tissue samples as an assessment of 

repeatability (precision) for all sample years. In 2009 

and 2013, field duplicates were added as an additional 

measure of quality control.

6. Following review, provide fish-tissue data to the Tribes, 

to the general public through the USGS National Water 

Information System, and in this report.

Sampling and Analysis

Field Sampling Methods

Fifteen rainbow trout (Oncorhynchus mykiss) were 

collected from each of the reservoirs (Mountain View, Lake 

Billy Shaw, and Sheep Creek Reservoirs) for each sample 

year (2007, 2009, and 2013). One fish from Lake Billy Shaw 

in 2013 was not analyzed because of an external injury. 

Sampling in 2007 was conducted in late May, and samples in 

2009 and 2013 were collected during the first week of June. 

Because one of the objectives was to sample a range of fish 

in sizes people are likely to catch and eat, experimental gill 

nets (mesh with several size openings) were used to reduce the 

effect of size selection based on a single mesh size (Hubert, 

1983). These nets were used to collect samples, with the 

exception of fish collected on Sheep Creek Reservoir in 2007 

when electrofishing was used. Fish were collected and stored 

in a live well on the boat during daily sampling events. Each 

fish was then measured, weighed, euthanized, and placed 

in separate clean, clear, zip-seal bags on wet ice; all fish 

were frozen within 24 hours of capture. Sample preparation 

followed guidelines in U.S. Environmental Protection Agency 

(2000) and Scudder and others (2008); final sample processing 

was conducted at the USGS Idaho Water Science Center’s 

sample preparation area in Boise, Idaho. Individual samples, 

consisting of a 1-in. skinless fillet, were taken from each fish 

just below the dorsal fin (Goldstein and others, 1996). The 

samples were placed in self-sealing plastic bags, labeled, 

and frozen; they later were packed on dry ice for shipment 

to the USGS Mercury Research Laboratory (USGS MRL) in 

Middleton, Wisconsin, for analysis.

Fish-Tissue Laboratory Analysis

The USGS MRL provided analysis of Hg in fish tissue 

consistent with USEPA Method 7473 (U.S. Environmental 

Protection Agency, 2007). This method provides a minimum 

detection limit of 0.008 mg/kg dry weight (dw), based on 

a 20–50 mg sample size. The detection limit is sufficiently 

low to quantify Hg concentrations in fish tissue at less 

than 0.22 mg/kg ww required for IFCAP fish consumption 

advisory assessments.

Atmospheric Mercury Deposition Data Analysis

The USEPA operates two mercury wet deposition sites 

in northern Nevada (NV02 and NV99), upwind of the Duck 

Valley Indian Reservation as part of the National Atmospheric 

Deposition Program’s (NADP) Mercury Deposition Network 

(MDN) (fig. 1). Wind vector and frequency analysis from a 

remote automated weather station on the reservation (Western 

Regional Climate Center, 2014) indicates that 44 percent of 

the prevailing winds are from the southwest compass quadrant, 

making site NV02, about 68 mi southwest of Sheep Creek 

Reservoir—the obvious choice for comparison of the Hg 

deposition rates in relation to reservoir fish samples. Details 

of the NADP methods and quality-assurance information are 

available online (National Atmospheric Deposition Program, 

2014a). In general, Hg deposition data are collected at the 

MDN site and analyzed weekly for mercury deposition, 

summarized and normalized by precipitation, and reported 

to the public as an annual precipitation weighted wet Hg 

deposition rate (National Atmospheric Deposition Program, 

2014b). Data from NADP for 2003–2013 were used to 

assess trends in Hg deposition on the reservation. Analysis 

of data outside of the tissue sampling year is helpful because 

elemental Hg may take years to enter into an aquatic system 

(Harris and others, 2007). Temporal trend testing was done 

through simple linear regression procedures using NCSS 10 

data analysis software (NCSS Statistical Software, 2015). The 

annual depositional rate at site NV02 was regressed against 

year; a slope that is significant (p<0.05) indicates a trend.
Sampling and Analysis 5

Statistical Analysis

Analysis of variance (ANOVA) one-way parametric 

analysis was used to test the significance of difference in mean 

fish-tissue Hg concentrations for individual reservoirs among 

years. Because Hg concentration was positively correlated 

to fish length (fig. 2), Hg concentration was normalized by 

fish length, and then log transformed to remove much of the 

heteroscedasticity (unequal variance) of residuals. Data were 

assumed to be normally distributed. Significant differences 

were determined if the F-ratio exceeded the critical value 

(p <0.05). For tests that indicated a significant difference, a 

multiple comparison test (Fisher’s LSD, α=0.05) was used 

to determine which years were significantly different. All 

ANOVA and multiple comparison statistical tests were done 

using NCSS 10 data analysis software (NCSS Statistical 

Software, 2015). A Mann-Kendall test also was run on the 

normalized and transformed data to determine monotonic 

change (trend) of Hg concentration in relation to time. The 

null hypothesis of “no change” is rejected if the S statistic is 

significantly different from 0 (p<0.05). The Mann-Kendall 

statistical test was performed with a USGS software package 

(Helsel and others, 2006).

r2 = 0.70

r

2 = 0.53

r2 = 0.44

0 

0.1 

0.2 

0.3 

0 

0.1 

0.2 

0.3 

0 

0.1 

0.2 

0.3 

0 10 20 30 40 50 60

Total mercury concentration, in milligrams per kilogram

Length, in centimeters

2007

2009

2013

Mountain View Reservoir, Idaho

Lake Billy Shaw, Nevada 

Sheep Creek Reservoir, Nevada 

Hatchery background samples from 

Black Canyon Trout Farm, Grace, Idaho

Expon. (All Fish) 

EXPLANATION

Figure 2. Mercury concentration in fish tissue by length from Duck Valley Indian Reservation reservoirs and hatchery background 

samples from the Black Canyon Trout Farm, southwestern Idaho and northern Nevada, 2007, 2009, and 2013.
6 Mercury in Rainbow Trout, Duck Valley Indian Reservation Reservoirs, Southwest Idaho and Northern Nevada, 2007, 2009, and 2013

Results and Discussion

Rainbow Trout Mercury Concentrations

Predatory fish generally tend to bioaccumulate Hg, 

with larger fish having higher Hg concentrations. Graphs of 

Hg concentration by fish length (fig. 2) show this principle 

for each of the sample years and each of the reservoirs. 

In aggregate, the correlation between fish length and Hg 

concentration was highest in 2007 (r2=0.70), and decreased in 

subsequent years to r2=0.53 (2009) and r2=0.44 (2013). 

Mean fish-tissue Hg concentrations significantly 

decreased in Mountain View Reservoir (p=0.01) between 

2007 (0.12 mg/kg ww) and 2009 (0.07 mg/kg ww) (table 1) 

and changed little between 2009 (0.07 mg/kg ww) and 2013 

(0.06 mg/kg ww). Results of the Mann-Kendall trend test 

showed a significant decreasing trend in Hg concentration in 

Mountain View Reservoir between 2007 and 2013 (p<0.001). 

Mean Hg concentration among the sample years in Lake 

Billy Shaw showed variance in Hg concentrations between 

sample years (2007, 0.12 mg/kg ww; 2009, 0.07 mg/kg 

ww; 2013, 0.09 mg/kg ww) with no significant difference 

between means (p=0.14), and no temporal trend observed 

(p=0.31). Mean Hg concentrations increased in Sheep Creek 

Reservoir(p <0.01) between 2009 (0.05 mg/kg ww) and 2013 

(0.10 mg/kg ww), with minimal change in concentration 

between 2007 (0.06 mg/kg ww) and 2009 (0.05 mg/kg ww) 

(table 1); this reservoir showed an increasing trend in Hg 

concentration (p<0.01). 

Hg concentrations exceeded the RPTE threshold of 

0.24mg/kg ww in only 3 of the 134 fish sampled in the 

reservoirs during the 3 sampling years, and did not exceed the 

IDEQ water-quality criterion of 0.30 mg/kg ww in any of the 

fish sampled in the reservoirs for any of the sampled years. In 

2007, Hg concentrations exceeded the RPTE threshold in one 

fish from each of the reservoirs—Mountain View Reservoir 

(0.26 mg/kg ww); Lake Billy Shaw (0.26 mg/kg ww); and 

Sheep Creek Reservoir (0.29 mg/kg ww) (table 1, fig. 3). Hg 

concentrations did not exceed the RPTE threshold limit in any 

of the fish sampled in 2009 or 2013 (fig. 3). 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 (Jim Vannoy, Idaho Department 

of Health and Welfare, written commun., December 11, 2009, 

and March 11, 2014).

Table 1. Statistical summary of annual sampling events for Duck Valley Indian Reservation reservoirs, 

southwestern Idaho and northern Nevada, 2007, 2009, and 2013.

[Site locations are shown in figure 1. mg/kg, milligram per killogram]

Sample

year

Mercury (mg/kg wet weight)

Standard 

deviation Minimum Maximum Number of samples

Geometric 

mean 

per site 

Median 

per site 

Mean 

per site 

Mountain View Reservoir, Idaho

2007 0.10 0.14 0.12 0.08 0.02 0.26 15

2009 0.06 0.06 0.07 0.03 0.02 0.14 15

2013 0.05 0.05 0.06 0.02 0.01 0.10 15

Lake Billy Shaw, Nevada

2007 0.10 0.11 0.12 0.07 0.03 0.26 15

2009 0.07 0.08 0.07 0.03 0.03 0.11 15

2013 0.08 0.09 0.09 0.03 0.05 0.16 14

Sheep Creek Reservoir, Nevada

2007 0.04 0.03 0.06 0.07 0.02 0.29 15

2009 0.05 0.04 0.05 0.03 0.02 0.10 15

2013 0.09 0.08 0.10 0.05 0.04 0.23 15
Results and Discussion 7

tac14-0959_fig03

2007 2009 2013 2007 2009 2013 2007 2009 2013

Total mercury concentration in fish tissue, in milligrams per kilogram wet weight

0.5

0.4

0.3

0.2

0.1

0

Idaho water-quality criterion (0.30 mg/kg)

RPTE threshold (average >0.24 mg/kg)

IFCAP action level (geometric mean of 0.22 mg/kg)

Mountain View Reservoir, Idaho Lake Billy Shaw, Nevada Sheep Creek Reservoir, Nevada

Largest point within 3rd quartile 

plus 1.5 times the IQR 

Median

25th percentile

75th percentile

Smallest point within 1st quartile 

minus 1.5 times the IQR 

Interquartile 

range (IQR)

X Outside values (values from 1.5 to 3.0 times the IQR)

Far-out values (values 3.0 times the IQR)

X Outside values (values 1.5 to 3.0 times the IQR)

Far-out values (values 3.0 times the IQR)

EXPLANATION

Figure 3. Sample concentration by year for rainbow trout sampled from Duck Valley Indian Reservation reservoirs, 

southwestern Idaho and northern Nevada, 2007, 2009, and 2013. RPTE threshold, reasonable potential to exceed 80 percent of 

the Idaho mercury water-quality criterion of 0.30 milligram per kilogram (mg/kg) wet weight mercury or greater than 0.24 mg/kg 

in an average of 10 fish; IFCAP action level, Idaho Fish Consumption Advisory Project recommends consideration of issuing a 

fish advisory when the geometric mean of mercury in 10 fish exceeds 0.22 mg/kg wet weight).
8 Mercury in Rainbow Trout, Duck Valley Indian Reservation Reservoirs, Southwest Idaho and Northern Nevada, 2007, 2009, and 2013

The variation in Hg concentrations in fish 

tissue between years in each reservoir may be due to 

confounding factors such as water-level fluctuations, 

light penetration limitations due to turbidity from 

suspended sediments or an abundance of organic 

matter, or other factors affecting methylation and 

demethylation rates (Wiener and others, 2007). 

Changes in fish population because of fish stocking 

practices and fish harvesting also may create an 

artifact in data and exemplifies the complexity of 

the systems (Wiener and others, 2007). The Tribes 

also stock the reservoirs with large hatchery trout 

to reduce predation from bass in the reservoirs 

(Edmond Murrell, Shoshone-Paiute Tribes thenDirector of Fish, Wildlife and Parks Department, 

oral commun., 2012). These hatchery trout have 

low Hg concentrations, and may be the reason there 

is variability in the Hg concentration in larger fish 

(fig. 2). Information provided by the Tribes shows that 

they stocked 24,000 lb of catchable fish in late April 

and early May in each of the sample years. In 2007 

and 2013, the hatchery stock was distributed equally 

among the three reservoirs, and ranged from 254 to 

355 mm (10–14 in.) in length; in 2009, 16,000 lb was 

placed in Mountain View Reservoir, and 8,000 lb in 

SheepCreek Reservoir, ranging from 254 to 330 mm 

(10–13 in.) in length (Jinwon Seo and Richard 

Edwards, Shoshone-Paiute Tribes Fish, Wildlife and 

Parks Department, written commun., 2015). The 

lengths should be considered estimates only, as one 

hatchery trout provided to the USGS for analysis in 

2013 was 462 mm (18 in.) in length.

Atmospheric Wet Mercury Deposition

From 2003 to 2013, the rate of wet Hg deposition 

at site NV02 (average 3.02 μg/m2) showed no 

significant temporal linear trend (p=0.79). Despite 

the decrease in total reported Hg compounds as 

point source (stack) emissions from Nevada mine 

operations from 2001 to 2013, there does not seem to 

be a decrease in the annual mercury deposition rate at 

site NV02 between 2003 and 2013 (fig. 4) (National 

Atmospheric Deposition Program, 2014b). This 

finding may be due to factors such as the locations 

of active gold processing sites in relation to regional 

wind patterns, or that the primary source of Hg to site 

NV02 may be from the global atmospheric Hg pool. 

Although there was an elevated wet Hg deposition 

rate measured in 2009 (5.66 μg/m2), there was no 

significant linear trend between 2003 and 2013 (fig. 4).

tac14-0959_fig04

0 

1 

2 

3 

4 

5 

6 

0 

1 

2 

3 

4 

5 

6 

2003 2005 2007 2009 2011 2013

Annual wet mercury deposition rate, 

in micrograms per square meter 

No linear trend, p = 0.79

Quality Control for Fish Analysis

The USGS MRL has extensive quality-assurance and quality 

control procedures (U.S. Geological Survey, 2014). Briefly, the 

USGS MRL uses International Atomic Energy Agency certified 

reference material 407, or Institute for National Measurement 

Standards certified reference material DORM-2, to verify laboratory 

instrument calibration before each daily sample run (Institute for 

National Measurement Standards, 1993; International Atomic 

Energy Agency, 2003). To determine instrument accuracy, CRM is 

analyzed at the beginning of the sample processing day, after every 

10 samples, and again at the end of the sample run. The relative 

percentage of difference of duplicates required by the USEPA 

is less than 24 percent (U.S. Environmental Protection Agency, 

2002). Triplicates of sample material are analyzed to determine 

repeatability (precision) and should be within 15 percent of the 

relative standard deviation for replicate analysis to meet USGS 

MRL standards. For this project, field replicates were analyzed 

to determine bias in sample processing. The goal for relative 

percentage of difference in field replicates was established at less 

than 20 percent.

Hg concentrations in QC samples are presented with the 

environmental sample results (table 3). Table 3 also includes 

laboratory CRM results used to verify equipment calibration 

(accuracy), and triplicate sample results from individual fish 

to assess repeatability (precision) for all sample years. The 

accuracy of the data was within the USEPA standard of less than 

24 percent of the most probable value for certified reference 

material for Hg (U.S. Environmental Protection Agency, 2002). 

Figure 4. Annual wet mercury deposition rate at Mercury 

Deposition Network site NV02, Lesperance Ranch, Nevada, 

2003–2013. Only complete data meeting National Atmospheric 

Deposition Program standards for data completion are plotted.
References Cited 9

Certified reference material recovery of Hg in QC samples 

ranged from 84.8 to 122 percent, within the required recovery 

of 76–124 percent of the theoretical value. The precision 

of the triplicate sample material was within 15 percent 

relative standard deviation in laboratory replicate analyses 

and ranged from 0.474 to 4.31 percent. Field duplicates 

also were analyzed as a measure of quality control, ranging 

from 0 to 14.7 percent, below the project goal of less than 

20 percent relative percent difference.

Summary

The U.S. Geological Survey, in cooperation with 

the Shoshone-Paiute Tribes of the Duck Valley Indian 

Reservation, monitored mercury (Hg) concentrations in 

rainbow trout to determine the risk of Hg exposure to Tribal 

members and the general public. Mean and median Hg 

concentrations were determined for 2007, 2009, and 2013, 

and all were less than the U.S. Environmental Protection 

Agency water-quality criterion of 0.30 milligram per kilogram 

(mg/kg) (wet weight, ww), and the Idaho Department 

of EnvironmentalQuality reasonable potential to exceed 

threshold of 0.24 mg/kg ww. Idaho Department of Health and 

Welfare toxicologists determined that the Hg concentrations 

in rainbow trout in this study would not warrant a fishconsumption advisory for this species.

Analysis of fish-tissue samples from Mountain View 

Reservoir indicated a significant decrease (p=0.01, analysis 

of variance test) in mean Hg concentrations between 2007 

(0.12 mg/kg ww) and 2009 (0.07 mg/kg ww), and no 

significant difference between 2009 (0.07 mg/kg ww) and 

2013 (0.06 mg/kg ww). Results of the Mann-Kendall trend 

test showed a decreasing trend in Hg concentration over 

time (p<0.001) for this reservoir. Mean Hg concentrations 

in Lake Billy Shaw indicated no significant difference 

between sample years (p=0.14) and no significant trend 

(p=0.31). Mean Hg concentrations in Sheep Creek Reservoir 

indicated little change between 2007 (0.06 mg/kg ww) and 

2009 (0.05 mg/kg ww), whereas there was a significant 

difference (p <0.01) between 2009 (0.05 mg/kg ww) and 2013 

(0.10 mg/kg ww); Hg concentration in this reservoir showed 

an increasing trend (p<0.01). There was no statistically 

significant linear trend indicating a relationship between a 

regional atmospheric source of Hg as measured at Mercury 

Deposition Network site NV02 and the Hg concentration 

increase in fish collected from Sheep Creek Reservoir during 

2009 and 2013. However, there was an elevated annual 

atmospheric deposition rate in 2009 (5.66 micrograms per 

square meter [μg/m2]), and terrestrial sources of Hg can take 

years or decades to enter aquatic ecosystems. Determining 

the source of Hg in Duck Valley Reservation’s reservoirs 

would require additional study. Without attributing cause, or 

identifying a source, Hg concentrations in trout tend to follow 

a pattern of increasing Hg concentrations in fish tissue from 

north to south on the reservation. A decreasing trend was 

noted in Mountain View Reservoir (p<0.00), no trend was 

found in Lake Billy Shaw (p=0.31), and an increasing Hg 

trend was found in Sheep Creek Reservoir (p<0.01). Overall, 

management of the fishery as well as other factors may affect 

the bioaccumulation of Hg in fish tissue. It was beyond the 

scope of this study to identify methylation processes that may 

be unique to each reservoir. Further study of Hg processing 

in the reservoirs may provide important clues for future 

management decisions concerning the Shoshone-Paiute 

Tribes fishery. 

Acknowledgments

We would like to thank the Shoshone-Paiute Tribes 

and, in particular, Heather Lawrence, Director for the Tribal 

Environmental Program, and John Crum, a former staff 

member, for their contributions to this investigation. This 

project would not have been possible without their untiring 

effort over many years. We also would like to express our 

appreciation to the former Director of Fish, Wildlife and 

Parks, Edmond Murrell, the current Director, Dr. Jinwon 

Seo, and their respective staff personnel for the assistance 

they provided.

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12 Mercury in Rainbow Trout, Duck Valley Indian Reservation Reservoirs, Southwest Idaho and Northern Nevada, 2007, 2009, and 2013

Table 2. Individual fish size, weight, and mercury concentration data, and statistical summaries 

for Duck Valley Indian Reservation reservoirs and hatchery background samples from the Black 

Canyon Trout Farm, southwestern Idaho and northern Nevada, 2007, 2009, and 2013.

[Site locations are shown in figure 1. Abbreviations: g, gram; mm, millimeter; mg/kg, milligram per kilogram]

Sample 

date Time

Total

length

(mm)

Weight

(g)

Mercury 

(mg/kg wet 

weight)

Mercury (mg/kg wet weight)

Geometric 

mean

per site 

Median 

per site

Mean 

per site

Mountain View Reservoir, Idaho

05-21-07 0830 400 747 0.06 0.10 0.14 0.12

0831 398 651 0.06

0832 510 1,522 0.17

0833 536 1,642 0.19

0834 480 1,376 0.19

0835 455 1,075 0.26

0836 442 884 0.14

0837 445 946 0.06

0838 473 1,195 0.14

0839 542 1,601 0.23

0840 475 1,207 0.22

0841 330 446 0.04

0842 335 412 0.02

0843 322 373 0.03

0844 312 337 0.06

06-01-09 1200 471 1,153 0.06 0.06 0.06 0.07

1201 493 1,289 0.14

1202 374 576 0.06

1203 396 711 0.08

1204 530 1,912 0.12

1205 363 529 0.02

1206 339 406 0.02

1207 360 495 0.08

1208 337 486 0.06

1209 335 460 0.06

1210 422 757 0.08

1211 301 318 0.04

1212 290 359 0.03

1213 440 846 0.05

1214 432 944 0.08

06-04-13 928 272 298 0.01 0.05 0.05 0.06

929 481 1,174 0.10

930 418 894 0.06

931 477 1,368 0.10

932 419 890 0.04

933 396 730 0.05

934 355 575 0.04

935 405 805 0.04

936 375 646 0.05

937 460 1,080 0.05

938 446 1,079 0.07

939 339 810 0.07

940 456 1,224 0.06

941 430 1,022 0.05

942 397 882 0.04
Table 2 13

Sample 

date Time

Total

length

(mm)

Weight

(g)

Mercury 

(mg/kg wet 

weight)

Mercury (mg/kg wet weight)

Geometric 

mean

per site 

Median 

per site

Mean 

per site

Lake Billy Shaw, Nevada

05-22-07 1400 395 605 0.07 0.10 0.11 0.12

1401 490 958 0.26

1402 470 1,150 0.25

1403 410 724 0.06

1404 430 830 0.10

1405 465 940 0.11

1406 485 1,030 0.16

1407 380 604 0.03

1408 355 462 0.03

1409 375 600 0.05

1410 400 665 0.12

1411 410 745 0.10

1412 500 1,150 0.19

1413 470 1,060 0.16

1414 390 675 0.08

06-02-09 1200 499 1,349 0.09 0.07 0.08 0.07

1201 414 685 0.09

1202 463 922 0.08

1203 431 805 0.06

1204 409 688 0.08

1205 293 292 0.10

1206 380 498 0.08

1207 370 405 0.09

1208 433 775 0.04

1209 342 438 0.03

1210 471 973 0.10

1211 332 380 0.03

1212 463 1,053 0.06

1213 307 329 0.03

1214 430 1,099 0.11

06-05-13 946 455 894 0.07 0.08 0.09 0.09

947 470 1,073 0.07

949 380 1,190 0.12

951 403 630 0.06

952 478 880 0.06

953 413 1,196 0.09

954 481 792 0.05

956 525 1,345 0.14

957 404 1,400 0.16

958 423 680 0.07

959 470 825 0.09

1000 441 1,094 0.11

1001 406 887 0.09

1003 272 837 0.09

Table 2. Individual fish size, weight, and mercury concentration data, and statistical summaries 

for Duck Valley Indian Reservation reservoirs and hatchery background samples from the Black 

Canyon Trout Farm, southwestern Idaho and northern Nevada, 2007, 2009, and 2013.—Continued
14 Mercury in Rainbow Trout, Duck Valley Indian Reservation Reservoirs, Southwest Idaho and Northern Nevada, 2007, 2009, and 2013

Sample 

date Time

Total

length

(mm)

Weight

(g)

Mercury 

(mg/kg wet 

weight)

Mercury (mg/kg wet weight)

Geometric 

mean

per site 

Median 

per site

Mean 

per site

Sheep Creek Reservoir, Nevada

05-22-07 1600 335 418 0.03 0.04 0.03 0.06

1601 392 568 0.29

1602 295 315 0.03

1603 345 430 0.05

1604 380 646 0.04

1605 345 464 0.04

1606 350 386 0.10

1607 435 834 0.03

1608 355 418 0.10

1609 335 390 0.03

1610 295 270 0.02

1611 300 294 0.02

1612 290 252 0.03

1613 275 228 0.03

1614 270 210 0.03

06-03-09 1200 409 693 0.09 0.05 0.04 0.05

1201 430 867 0.10

1202 418 761 0.07

1203 416 873 0.10

1204 386 607 0.06

1205 329 409 0.03

1206 390 723 0.06

1207 310 357 0.04

1208 316 372 0.02

1209 275 205 0.02

1210 297 276 0.02

1211 268 216 0.03

1212 313 326 0.02

1213 296 264 0.04

1214 438 806 0.09

06-06-13 957 425 762 0.10 0.09 0.08 0.10

959 447 1,010 0.07

1000 535 1,258 0.04

1001 450 1,069 0.23

1002 390 704 0.11

1003 387 584 0.08

1004 403 638 0.12

1006 350 398 0.04

1007 489 1,340 0.16

1008 389 565 0.08

1009 449 887 0.10

1010 435 783 0.07

1011 369 552 0.06

1012 474 1,155 0.19

1013 415 710 0.08

Table 2. Individual fish size, weight, and mercury concentration data, and statistical summaries 

for Duck Valley Indian Reservation reservoirs and hatchery background samples from the Black 

Canyon Trout Farm, southwestern Idaho and northern Nevada, 2007, 2009, and 2013.—Continued
Table 2 15

Table 2. Individual fish size, weight, and mercury concentration data, and statistical summaries 

for Duck Valley Indian Reservation reservoirs and hatchery background samples from the Black 

Canyon Trout Farm, southwestern Idaho and northern Nevada, 2007, 2009, and 2013.—Continued

Sample 

date Time

Total

length

(mm)

Weight

(g)

Mercury 

(mg/kg wet 

weight)

Mercury (mg/kg wet weight)

Geometric 

mean

per site 

Median 

per site

Mean 

per site

Black Canyon Trout Farm, Grace, Idaho

05-04-07 1215 355 500 0.03 0.04 0.04 0.04

1216 310 326 0.03

1217 355 532 0.04

1218 355 548 0.04

1219 365 586 0.05

04-22-09 1200 297 240 0.01 0.02 0.02 0.02

1201 324 275 0.02

1202 309 245 0.01

1203 297 235 0.03

1204 306 245 0.01

05-21-13 1125 330 365 0.01 0.01 0.01 0.01

1130 360 505 0.01

1131 315 290 0.01

1132 334 450 0.01

1133 415 690 0.02

1134 462 1,070 0.02

1135 340 425 0.01
16 Mercury in Rainbow Trout, Duck Valley Indian Reservation Reservoirs, Southwest Idaho and Northern Nevada, 2007, 2009, and 2013

Certified — 2007

Laboratory 

identification

Date of 

analysis

Mercury, 

ng/g dry 

weight

Certified 

reference 

material recovery 

(percent)

IAEA 407 08-10-07 226 102

222 100

231 104

IAEA 407 08-13-07 226 102

239 108

244 110

232 105

236 106

256 115

IAEA 407 08-14-07 232 105

238 107

270 122

237 107

238 107

250 113

IAEA 407 08-15-07 239 107

247 111

254 114

IAEA 407 08-16-07 243 110

244 110

232 105

242 109

Laboratory triplicate — 2007

Laboratory 

identification

Date of 

analysis

Mercury, 

ng/g dry 

weight

Triplicate

relative standard

deviation 

(percent)

MSC603D 08-13-07 148 0.474

148

147

MSC617D 08-13-07 117 1.11

115

115

MSC631D 08-14-07 510 1.48

496

507

MSC645D 08-14-07 286 0.698

290

287

MSC659D 08-15-07 133 1.18

133

130

Certified — 2007

Laboratory 

identification

Date of 

analysis

Mercury, 

ng/g dry 

weight

Certified 

reference 

material recovery 

(percent)

DORM-2 08-10-07 4,440 95.7

4,480 96.5

4,480 96.6

DORM-2 08-13-07 4,240 91.4

4,480 96.6

4,600 99.1

4,690 101.0

4,400 94.8

4,660 100.0

DORM-2 08-14-07 4,310 92.9

4,490 96.8

4,510 97.3

4,750 102.0

4,680 101.0

4,520 97.4

DORM-2 08-15-07 4,430 95.6

4,380 94.3

4,500 97.0

DORM-2 08-16-07 4,480 96.6

4,560 98.4

4,460 96.1

4,620 99.6

Table 3. Quality-control results for analysis of total mercury in fish from Duck Valley Indian Reservation reservoirs and hatchery 

background samples from the Black Canyon Trout Farm, southwestern Idaho and northern Nevada, 2007, 2009, and 2013.

[Certified reference material from the International Atomic Energy Agency (IAEA), laboratory identification number beginning with International Atomic 

Energy Agency (2003); a description of IAEA-407 is available at http://www.iaea.org/nael/refmaterial/iaea407.pdf. Certified reference material from the 

Institute for National Measurement Standards, National Research Council of Canada, laboratory identification number beginning with DORM-2; a description 

of DORM-2 is available at http://www.nrc-cnrc.gc.ca/obj/doc/solutions-solutions/advisory-consultatifs/crm-mrc/dorm_2_e.pdf. Triplicate samples from a 

single fish at a sampling site (laboratory identification samples beginning with MSC) were analyzed separate from the original sample for laboratory method 

repeatability (precision) and reported as relative standard deviation (RSD), RSD = Standard deviation of the three replicate concentrations divided by the 

average of those replicates. Field duplicates are samples from a single specimen collected as an assessment of quality control. Results are reported as relative 

percent difference (RPD), where {(x1 – x2)/[x1 + x2)/2]100, and x = sample concentration. Abbreviation: ng/g, nanograms per gram]
Table 3 17

Certified – 2009

Laboratory 

identification

Date of 

analysis

Mercury, 

ng/g dry 

weight

Certified 

reference 

material recovery 

(percent)

IAEA 407 09-22-09 201 90.5 

222 100.0 

225 101.0 

219 98.8 

220 99.0 

224 101.0 

09-25-09 222 99.9 

218 98.2 

220 99.0 

217 97.7 

219 98.8 

208 93.7 

220 99.2 

Laboratory triplicate — 2009

Laboratory 

identification

Date of 

analysis

Mercury, 

ng/g dry 

weight

Triplicate

relative standard

deviation 

(percent)

MSC335I 09-25-09 406 3.93

433

404

306 2.58

292

306

MSC356I 09-25-09 183 3.93

171

183

MSC348I 09-22-09 490 4.31

506

534

MSC340I 09-25-09 118 1.77

122

121

MSC338I 09-22-09 211 2.06

219

212

Field duplicate — 2009

Laboratory 

identification

Sample

date

Mercury, 

ng/g dry 

weight

Relative

percent 

difference

MSC316I 04-22-09 0.01 10.8 

MSC315I 04-22-09 0.01

MSC327I 06-02-09 0.03 5.47 

MSC326I 06-02-09 0.04

MSC364I 06-01-09 0.12 3.68 

MSC363I 06-01-09 0.13

MSC353I 06-01-09 0.08 4.9 

MSC352I 06-01-09 0.09

MSC342I 06-03-09 0.02 0.00439

MSC341I 06-03-09 0.02

Table 3. Quality-control results for analysis of total mercury in fish from Duck Valley Indian Reservation reservoirs and hatchery 

background samples from the Black Canyon Trout Farm, southwestern Idaho and northern Nevada, 2007, 2009, and 2013.—Continued
18 Mercury in Rainbow Trout, Duck Valley Indian Reservation Reservoirs, Southwest Idaho and Northern Nevada, 2007, 2009, and 2013

Certified — 2013

Laboratory 

identification

Date of 

analysis

Mercury, 

ng/g dry 

weight

Certified 

reference 

material recovery 

(percent)

IAEA 407 10-23-13 243 109.0 

241 108.0 

250 113.0 

251 113.0 

263 118.0 

10-24-13 229 103.0 

231 104.0 

248 111.0 

230 104.0 

233 105.0 

240 108.0 

10-25-13 224 101.0 

228 103.0 

227 102.0 

238 107.0 

233 105.0 

10-29-13 212 95.5 

226 102.0 

216 97.4 

233 105.0 

10-31-13 204 91.8 

198 89.0 

199 89.5 

188 84.8 

Laboratory triplicate — 2013

Laboratory 

identification

Date of 

analysis

Mercury, 

ng/g dry 

weight

Triplicate

relative standard

deviation 

(percent)

MSC829S 10-23-13 307.0 0.529 

304.0 

305.0 

MSC889S 10-23-13 530.0 3.49 

561.0 

565.0 

MSC837S 10-24-13 752.0 0.416 

748.0 

754.0 

MSC862S 10-24-13 171.0 0.932 

169.0 

172.0 

MSC881S 10-24-13 377.0 1.27 

383.0 

387.0 

MSC890S 10-25-13 495.0 3.89 

535.0 

520.0 

MSC894S 10-25-13 266.0 0.53 

265.0 

268.0 

MSC870S 10-29-13 814.0 1.71 

820.0 

841.0 

MSC850S 10-31-13 56.7 3.96 

54.1 

52.5 Field duplicate — 2013

Laboratory 

identification

Sample

date

Mercury, 

ng/g dry 

weight

Relative

percent

difference

MSC849S 06-04-13 0.10 2.9 

MSC848S 06-04-13 0.11

MSC861S 06-04-13 0.05 14.7 

MSC844S 06-04-13 0.06

MSC336U 06-05-13 0.07 4.72 

MSC337U 06-05-13 0.06

MSC834S 06-05-13 0.05 6.48 

MSC828S 06-05-13 0.05

MSC835S 06-05-13 0.09 4.1 

MSC838S 06-05-13 0.08

MSC888S 06-06-13 0.10 1.97 

MSC889S 06-06-13 0.10

MSC882S 06-06-13 0.12 0.796 

MSC883S 06-06-13 0.11

MSC881S 06-06-13 0.08 7.49 

MSC893S 06-06-13 0.09

Table 3. Quality-control results for analysis of total mercury in fish from Duck Valley Indian Reservation reservoirs and hatchery 

background samples from the Black Canyon Trout Farm, southwestern Idaho and northern Nevada, 2007, 2009, and 2013.—Continued
Publishing support provided by the U.S. Geological Survey 

Science Publishing Network, Tacoma Publishing Service Center

For more information concerning the research in this report, contact the 

Director, Idaho Water Science Center

U.S. Geological Survey 

230 Collins Road

Boise, Idaho 83702

http://id.water.usgs.gov
Williams and others—Mercury in Rainbow Trout, Duck Valley Indian Reservation Reservoirs, Southwest Idaho and Northern Nevada, 2007, 2009, and 2013—Scientific Investigations Report 2015–5079

ISSN 2328-0328 (online)

http://dx.doi.org/10.3133/sir20155079