EPA-910-R-16-003
February 2016
United States
Environmental Protection
Agency
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Assessment of Mercury in
Fish Tissue from Pacific
Northwest Lakes
EPA Region 10 Report
Author:
Lillian G. Merger
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Assessment of Mercury in Fish Tissue from Pacific Northwest Lakes
EPA Region 10 Report
February 2016
Author:
Lillian G. Herger
U.S. Environmental Protection Agency, Region 10
Office of Environmental Assessment
1200 Sixth Avenue, Suite 900
Seattle, Washington 98101
Publication Number: EPA 910-R-16-003
Citation:
Herger, L.G. 2016. Assessment of mercury in fish tissue from Pacific Northwest lakes. Report
Number EPA-910-R-16-003. U.S. Environmental Protection Agency, Region 10, Seattle,
Washington.
This document is available at:
http://www.epa.gov/fish-tech/reports-and-fact-sheets-about-fish-consumption-and-human-health
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Contents
List of Figures iv
List of Tables iv
List of Maps iv
List of Appendices iv
Abstract 1
Introduction 1
Study Design 3
A. Sample Frame 3
B. Fishable Lake Selection and Extent 4
C. Landscape Description of Region 10 Fishable lakes 5
D. Target Species and Sample Hierarchy 6
Methods 6
A. Field Methods 6
B. Laboratory Analysis Methods 7
C. Data Summary Methods 7
Results and Discussion 8
A. Fish Collection Results 8
B. Analysis Results 9
C. Comparison to Other Studies 10
D. Feasibility of Fish Tissue as NLA Indicator 11
Conclusions 12
Acknowledgements 13
References... .. 14
Assessment of Mercury in Fish Tissue
from Pacific Northwest Lakes
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List of Figures
Figure 1. Descriptive features of the fishable lake inference population expressed as percent
(N=905) 5
Figure 2. Cumulative distribution frequency plot of fish tissue Hg by percent of lakes. Red
dashed lines indicate the lake percentile corresponding to three screening values (inferred
population = 905 lakes) 9
List of Tables
Table 1. Species included in the lake fish tissue mercury estimates 8
Table 2. Percentiles and lake estimates for mercury concentrations (ug/kg ww) 9
Table 3. Exceedences of three mercury screening values (inferred population = 905 lakes) 10
Table 4. Lake predator fish tissue concentrations of Hg (ug kg1 ww). Comparison of results to
nationwide and PNW region data from 2000-2003 National Lakes Fish Tissue study 10
List of Maps
Map 1. Locations of the 50 sampled fishable lakes for the PNW states shown in the Western
Mountains (green) and Xeric (brown) aggregated level III ecoregions 4
List of Appendices
Appendix A. Lake sites sampled for fish in Idaho, Oregon, and Washington, 2012-2014 17
Appendix B. List of species targeted for lake fish tissue sampling based on likely sportfish
species present in sample lakes 19
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Abstract
Sportfish collected from 50 lakes in the three Pacific Northwest states of Idaho, Oregon, and
Washington during 2012-2014 were analyzed for mercury. A probabilistic design was used to
determine the region-wide concentration offish tissue mercury in lakes that may be used for
recreational fishing. Mercury was detected in all fish samples. The EPA tissue-based water quality
criterion of 300 jig kg"1 was exceeded in 11% of the 905 lakes represented by the sample lakes. The
results are compared to other regional fish tissue mercury studies and the feasibility of adding this
indicator into future EPA large-scale lake assessments is discussed.
Introduction
Mercury is one of the most toxic metals found in the environment. Mercury is a naturally occurring
metal that cycles among the atmosphere, water, and sediments. Natural releases include rock
weathering as well as emissions from geothermal areas and volcanoes. Human activities increase
the amount of mercury cycling in the environment. Significant amounts of mercury are emitted
from metal smelters, coal-burning power plants, and industrial waste incinerators. Atmospheric
deposition is the most significant pathway transporting mercury through the environment (Driscoll
et al. 2013). Other pathways include runoff, point discharges, and releases from metals mining.
In aquatic systems, the cycling of mercury prolongs the influence of human-caused mercury
compounds (Hudson et al. 1995). Biotic processes in both the water column and sediment convert
the inorganic form to the toxic methylated form. Methylmercury is the form that accumulates in
fish tissue.
Fish have two routes of mercury uptake. Fish concentrate mercury from water (bioconcentration)
and through their diet (bioaccumulation). Fish typically accumulate only small amounts of
methylmercury through gill tissue and directly from the water column (Spry and Wiener 1991).
The majority of the accumulated mercury is acquired through the food web. Fish that have a
moderate to high position in the food web accumulate more mercury and mercury concentrations
in their tissue increases as they grow. Accordingly, tissue mercury concentrations in upper trophic
level fish species best reflect the amount of mercury available to other higher trophic levels
(including humans).
Consuming fish that contain mercury can cause toxic effects to humans. Exposures to mercury can
affect the human nervous system and harm the brain, heart, kidneys, lungs, and immune system
(WHO 2003). The most common way people are exposed to mercury is by eating fish or shellfish
that are contaminated with mercury. Because methylmercury affects the developing human
nervous system (NRC 2000), fish advisories based on elevated mercury concentrations have lower
consumption recommendations for young children, nursing mothers, and women who are or
might become pregnant than they have for the rest of the population. North American government
agencies have worked to reduce cycling of mercury. An analysis of global emissions inventories by
Zhang et al. (2016) estimated a 30% decrease in elemental mercury emissions occurred between
1990 and 2010 with the largest decreases occurring in North America and Europe. They attribute
these decreases to local and regional efforts in the form of phasing mercury out of commercial
products, controls on coal-burning power plants, and power plant conversion to natural gas.
Assessment of Mercury in Fish Tissue
from Pacific Northwest Lakes
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In the Pacific Northwest (PNW), lakes are an important and diverse aquatic resource. They support
complex ecological interactions and provide habitat for fish, birds and wildlife. Lakes of the region
are valued by humans as open-space and for recreation and fishing. Fish tissue mercury levels
are not broadly understood in the PNW lakes. The only previous region-wide fish tissue toxics
assessment in the Pacific Northwest was the 2000-2003 National Lake Fish Tissue Study. This was
a nationwide sample of 500 lakes that included 30 lakes in the Pacific Northwest states (Idaho,
Oregon, and Washington). Smaller scale studies of lake fish tissue have been conducted by states
and EPA, but these studies are not intended to describe the condition of the entire PNW region.
The EPA, in partnership with states and tribes, conducts broad-scale ecological surveys of
aquatic resources in order to evaluate their status and to examine associations between ecological
condition and natural and anthropogenic influences. The long-term goal of these surveys is to
determine if these aquatic resources are in an acceptable or unacceptable condition relative to a set
of environmental or ecological values.
EPA has conducted two studies of the nation's lakes (USEPA2009, USEPA2016). These
assessments evaluate ecological condition using a large suite of water quality, biological and
recreation indicators. Although fish tissue toxics are considered an important indicator for
assessing recreational quality of aquatic resources, fish collection has been beyond the scope for
the national lakes surveys. Although tissue studies were not included in the national survey, EPA
Region 10 collected fish tissue mercury data from the same PNW sampling sites as the 2012
National Lakes Assessment (USEPA 2016). Collection of these data was considered an important
opportunity by RIO for several reasons:
1. Characterizing mercury levels in fish, water and sediment is an objective of the Region
10 mercury strategy (USEPA 2008). Determining current mercury levels in fish across the
PNW region is considered a key step to defining the geographic extent of elevated mercury
concentrations is fish tissue.
2. Although a decade has passed since EPAs last nationwide assessment of contaminants in fish
tissue, there are no current plans by EPA to conduct another, or to do follow-up monitoring to
toxics in fish tissue on a national scale. This necessitates RIO conducting follow-up monitoring
of toxics in fish tissue for trend analysis in the Pacific Northwest.
3. Having fish tissue data from the same lakes that were sampled as part of the 2012 National
Lakes Assessment means compatible data were collected for other lake metrics (water quality,
landscape characteristics, sediment mercury concentrations). These will be available to
complement the fish tissue mercury analysis.
The objective of this Region 10 Lakes Fish Tissue Mercury Assessment is to collect predator
fish species from a subset of the lakes that were sampled for ecological condition as part of the
National Lakes Assessment 2012 in Idaho, Oregon, and Washington. The fish tissue was analyzed
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for mercury to determine concentrations in recreational fish species. These data are used to address
the following questions:
What are mercury concentrations in fillet tissue of common sportfish from lakes in the Pacific
Northwest states (Idaho, Oregon, and Washington) that are used by the public for fishing?
What is the estimated percentage of PNW lakes with mercury concentrations in sportfish tissue
that are above levels of potential concern for humans?
What is the trend in fish mercury concentration in these lakes over time?
Study Design
A. Sample Frame
The study area is the EPA Region 10 states of Idaho, Oregon and Washington. Assessing a large
area requires a study design that can adequately capture the variation across the landscape and also
be descriptive of the entire resource of interest. The following is a description of the survey design
of the 2012 National Lakes Assessment (NLA), which serves as the basis for this PNW fish tissue
mercury study design (USEPA2016).
The National Lakes Assessment, as do all of the EPA National Aquatic Resource surveys, uses
a probability design, which is similar to a public opinion poll. A subset of lakes are selected for
sampling from an explicitly defined set of lakes of interestthe 'target population' (Peck et al
2013). The resulting data are used to make inferences to this greater target population of lakes
(Peck et al. 2013). The sample lakes are selected using a probability-based sampling method
to ensure that they are representative of the target population of lakes. This design has two
advantages: 1) prevents site selection bias and 2) allows for statistically valid inferences to the
entire target population of lakes (Stevens and Olsen 1999 and 2004).
The site sample generated for the 2012 NLAis a probability sample of lakes representing a
target population of lakes in the PNW (USEPA2016). The study sample frame (potential sample
locations) consisted of all lakes (lakes, reservoirs, and ponds) that are permanent water bodies
within Oregon, Idaho, and Washington. The landscape data used to generate this set of lakes was
the USGS/EPA National Hydrography Dataset Plus, Version 2 (NHDPlus). For the PNW states,
this dataset consisted of 8,317 features that could potentially be lakes included in the NLA survey.
This dataset was screened using the following criteria required for the target population:
surface area > 1 ha (2.47 acres)
> 0.1 ha open, unvegetated, water surface area
> 1 meter depth
minimum residence time of one week
excludes 'working' lakes used for tailing disposal, sewage treatment, etc.
excludes saline coastal water bodies and those under tidal influence
This screening reduced the potential sample locations to a set of 5,013 lakes that represent the
target population for the PNW portion of the 2012 National Lakes Assessment.
Assessment of Mercury in Fish Tissue
from Pacific Northwest Lakes
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Sample lakes were selected randomly from this target population in proportion to their occurrence
within six size categories (Overton et al. 1990, Stevens and Olsen 2004). Each potential sample
lake was evaluated to ensure that it met the target lake screening criteria as well as the following
criteria for 'sampleability': 1) no existing safety issues that would prohibit sampling, 2) not
excessively remote so sampling with a boat could be conducted in a reasonable timeframe, and 3)
permission to access sample sites would be granted by landowners. A final set of 100 lakes were
sampled in the Pacific Northwest states (ID, OR, WA), which represented an inference population
of 2,479 lakes.
The target population was sampled in a spatially-restricted manner so that the distribution of the
sample sites had approximately the same spatial distribution as the target population. This was
achieved by using an unequal probability sample method to ensure distribution of samples of sites
by size, state, and major ecoregion types (mountainous/humid v. xeric). For example, in this study
large lakes were given higher probability of being selected for sampling than small lakes. This
effectively increases the probability of having large lakes selected for the sample so that the sample
is not dominated by the small lakes, which are much more common across the landscape. This
variable selection probability by lake size is accounted for when making the regional estimates
by using site weighting factors. Each site is assigned a weight, based on the occurrence of its type
(size-class) in the target population. It is important to note that any inferences to the entire target
population based simply on the un-weighted site data are inaccurate.
B. Fishable Lake Selection and Extent
The lakes of interest for this mercury study are 'fishable' lakes, where fishable is defined as lakes
that are useable and accessible by anglers to capture fish for consumption. These fishable lakes
form the target population for this study. The NLA 2012 target population of sample lakes was
useable as the base list of sample lakes for this PNW fish tissue mercury study because the fishable
lakes target population is more restrictive than the NLA 2012 lakes population. The list of NLA
sample lakes described above for the three
states was restricted to a 'fishable' target
population by applying the following two
criteria to validate angler useability and
accessibility for the purpose of angling:
1) sites must have public access with
ability to harvest fish legally (this would
include private water bodies that have an
agreement in place with state fisheries
agencies so that angler access is allowed)
and 2) sites must contain at least one
species known to be commonly consumed
by anglers of the region (salmonids,
centrarchids, etc.) (USEPA2000a).
The lakes were carefully evaluated for
fishability and selected from the lists of
NLA sampled lakes of the three states.
Map 1. Locations of the 50 sampled fishable lakes for the
PNW states shown in the Western Mountains (green) and Xeric
(brown) aggregated level III ecoregions.
United States Environmental Protection Agency
February 2016
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The first 16 or 17 lakes that meet the fishable criteria constitute the probability sample of the
Fishable Target Population for each of the three states. This process was repeated for each state
to generate a 50 lake list. The resulting 50 fish-sampleable lakes were sampled over three field
seasons 2012-2014 (Appendix A). Probability design sample weights applied to each lake result in
a total inference population of 905 fishable lakes of the PNW. Fishable lakes in the region can be
described based on this inference population.
C. Landscape Description of Region 10 Fishable lakes
Descriptive features of the fishable lake
inference population based on the 50 lakes
sampled are shown in Figure 1. Fishable lakes
are predominately in the Western Mountains
ecoregion with < 20% in the Xeric ecoregions
(USEPA2003). Most of the fishable lakes
are in the Northern Rockies, followed by the
Cascades, Coast Range, and Puget Lowlands
subecoregions (Level III ecoregions).
The size of most of the fishable lakes was in the
10-50 ha surface area size category and none
of the lakes were in the smallest size category
(<4 ha). The origin of most of the lakes is either
natural or natural with some human influence
(e.g., flow alteration or construction) to enhance
the size of the lake. The rest of the lakes are
either entirely human-made or the result of dam
construction.
The biological productivity of the fishable lakes
varies from highly productive (hyper-eutrophic)
to very low productivity (oligotrophic). About
two-thirds of the lakes have medium to low
productivity and less than 10% are in the hyper-
eutrophic category.
500+
100-500
50-100
10-50
4-10
Manmade
Reservoir
Natural-
enhanced
Natural
Hyper-
eutrophic
Eutrophic
Meso trophic
Oligotrophic
Surface Area (ha)
10
20
Lakes %
Lake Origin
30
40
10 20 30 40 50 60 70
Lakes %
Trophic Status
10 20
Lakes %
30
40
Figure 1. Descriptive features of the fishable
lake inference population expressed as
percent (N=905).
Assessment of Mercury in Fish Tissue
from Pacific Northwest Lakes
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D. Target Species and Sample Hierarchy
Resident (non-migratory) sportfish species were targeted for sampling, since these are the
species that would be captured and consumed by humans. In the PNW lakes, most game species
are typically predatory (carnivorous) fish that feed on invertebrates, fish, or both. These can
be categorized into two main sportfish groups, salmonids (trout, char, and whitefish) and non-
salmonids (centrarchids, percids, and ictalurids).
Since species that are predators tend to bioaccumulate mercury, these fish provide more insight
into levels of mercury that may be in sportfish and thus have implications for human consumers
as compared to bottom-dwelling species, which tend to be detritivores, herbivores, or omnivores.
Other game species considered to be bottom-dwellers (e.g., carp and suckers), as well as non-game
species (e.g., shiners) were rejected as sample species. Finally, state and federally listed Threatened
and Endangered species were avoided. Bull trout was the only T&E species potentially present in
these PNW target sample lakes.
The individual fish targeted were adult fish that were within the length ranges typically consumed
by anglers for each species and within the legal harvest limits as stated by the regulations
published for each of the three states. The fish collection goal at each lake was 3-10 fish from at
least one size class of one sportfish species. Additional size classes and species were collected if
available. These additional samples also had to meet the size and species criteria for sportfish of
the legal collectable/edible size.
The species available for sampling vary by lake thus a variety of species were analyzed for
mercury across all of the sample lakes. Many lakes had both salmonids and non-salmonid sportfish
species as part of the fish assemblage. At these lakes, we attempted to collect a species representing
both types of sportfish. This increased the likelihood of having a more consistent species/trophic
level represented across all sites. The list of sportfish species that were likely to be sampled based
on the eligible target species and knowledge of PNW lakes is included as Appendix B.
Methods
A. Field Methods
Field sampling was conducted between April and October in the years 2012-2014. Boat
electrofishing, angling, and gillnets were the primary gear types. The fish collection method varied
to optimize the potential to capture the target species and to minimize sampling effort at each
lake. Many lakes in the area are stocked, typically with rainbow trout. We modified sampling
approach in these lakes to avoided newly planted fish including collecting larger-sized trout that
had likely overwintered and timing our sampling to maximize the time since the last fish planting
event. Information from fisheries managers on lake stocking, as well as species presence, lake
characteristics, and T&E species, was used to customize sampling to adapt for particular situations.
Captured fish were identified to species and individuals meeting the species and size criteria
were retained. These fish were measured, weighed, and grouped by species and similar size (each
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fish within 75% of the length of the other individuals). Whole fish were packaged, frozen, and
delivered to the EPA Region 10 Laboratory in Manchester, Washington where they were stored
at -20°C. Sample integrity procedures are detailed in the Quality Assurance Project Plan (QAPP)
(USEPA 2012).
B. Laboratory Analysis Methods
Total mercury was the analyte of interest. Total mercury is recommended for screening level
monitoring as opposed to methylmercury because this adds a conservative approach when
comparing to methylmercury screening criteria. Studies have found that methylmercury can
account for over 90% of mercury concentration in predator species (USEPA2006). Fillet (muscle)
was analyzed as this is the portion of the fish commonly consumed by humans.
The chemical analysis was performed by EPA chemists. Fish were partially thawed and
approximately one gram of muscle tissue was excised from each fish. All fish tissue samples
were analyzed individually using EPA method 7473 (Mercury in solids and solutions by thermal
decomposition, amalgamation, and atomic absorption spectrophotometry, USEPA 1998). The
method was conducted on a Direct Mercury Analyzer (Milestone Inc.), which uses controlled
heating in an oxygen decomposition furnace to liberate mercury from the fish tissue. The analytical
parameters and other aspects of the laboratory methods are detailed in the QAPP (USEPA 2012).
C. Data Summary Methods
Fish data were combined for the analysis by calculating the arithmetic mean Hg value for each
of the 50 lakes. Although fish species and sizes vary among sites, the unifying feature is that all
fish were predators and were part of the fish assemblage that would be targeted and consumed by
anglers. Thus, it was reasonable to combine results by lake to evaluate the mercury concentration
in sportfish as a whole. Also, we are interested in longer-term exposure (rather than a single meal)
and using the mean value is appropriate to reduce within-sample variability. The lake site weights
described above in the study design section were applied to generate the probability estimate
for the inference lake population. R statistics software (version 3.1.1, R Core Team 2013) and
the Spsurvey package (Kincaid and Olsen 2015) were used to estimate the percentiles and the
cumulative distribution of tissue mercury concentrations of the predator samples.
Results were compared to USEPA's fish tissue methylmercury criterion of 300 jig kg"1 wet weight
(ww) to protect the health of individuals who eat fish (USEPA 2001). This criterion is based on
adult consumption rate of 17.5 grams (g) offish per day. Two other screening values based on
higher consumption rates relevant to the PNW were also compared to the mercury tissue results.
A 'general population' screening value of 120 jig kg-1 ww is based on a consumption rate of
approximately two fish meals per week (59.7 g/day) (Dave McBride, WA Department of Health,
Pers. Comm. 1/28/15). This is the amount offish the American Heart Association recommends
eating as part of a healthy diet. Finally, a 'high consumer' screening value of 40 jig kg-1ww based
on 175 g/day consumption rate was used for comparison. This is the Oregon State fish tissue
standard (ODEQ 2014), which accounts for the portion of the population that eats more fish than
average consumers. All screening values are for non-carcinogenic effects of mercury, which are
discussed in detail in EPA's guidance on fish advisories (USEPA 2000b).
Assessment of Mercury in Fish Tissue
from Pacific Northwest Lakes
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Results and Discussion
A. Fish Collection Results
Each sample lake had unique constraints for obtaining fish. Practical considerations such as gear
type, timing, and fish abundance and conditions on the day of sampling dictated the species and
size classes actually captured. Fishing was difficult at some lakes where the optimum sample
composite size of five to ten individuals was not obtained. Adequate fish tissue was obtained for
analysis from all 50 lakes that were sampled. Washington Department of Ecology supplied tissue
samples in the form of processed aliquot for the Moses Lake site.
Over the three year period (2012-2014) 481 fish were collected from the 50 sample lakes. As
expected, the numbers offish, size classes, and species collected varied among lakes. Each lake
had a fish sample one size class for one species. Two size classes for one species were obtained
at 14 sites and three size classes at five sites. Two different species were collected at six sites.
Atotal of 13 species were included in the analysis representing four fish families (Table 1). The
most common species among the 50 sample lakes was rainbow trout followed by largemouth bass,
collected in 28% and 24% of the lakes, respectively. Species sampled were fairly evenly split
between salmonids and non-salmonids. At least one salmonid was collected at 48% (24) of sites
and at least one non-salmonid was collected at 58% (29) of sites.
Table 1. Species included in the lake fish tissue mercury estimates.
Sample type
salmonids
Non-salmonids
Family
Salmonidae
Centra rchidae
Percidae
Ictaluridae
Species scientific name
Oncorhynchus my kiss
Salvelinus fontinalis
Oncorhynchus clarkia
Oncorhynchus nerka
Micropterus sal mo ides
Micropterus dolomieu
Lepomis macrochirus
Lepomis gibbosus
Pomoxis nigromaculatus
Ambloplites rupestris
Perca flavescens
Sander vitreus
Ameiurus nebulosus
Species common
name
rain bow trout
brook trout
cutthroat trout
kokanee
largemouth bass
smallmouth bass
bluegill
pumpkinseed
black crappie
rock bass
yellow perch
walleye
brown bullhead
Adult Feeding
typeb
Invert/piscivore
Invert/piscivore
Invert/piscivore
Invertivore
Piscivore
Piscivore
Invert/piscivore
Invert/piscivore
Invert/piscivore
Invert/piscivore
Invert/piscivore
Piscivore
Invert/piscivore
Number
of lakes
14
5
4
2
12
3
3
2
2
1
5
1
2
"Includes all cutthroat trout subspecies.
bFrom Zaroban et al. 1999.
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B. Analysis Results
As previously stated, the sample of 50 lakes represents an inference population of 905 lakes.
Summary statistics are calculated using site weights to accurately represent this inference
population. All of the fish samples had quantifiable levels of Hg that exceeded the Minimum
Reporting Level (the smallest measured concentration of a substance that can be reliably
measured) of 0.0125 mg kg ww based on standard mass of 80 mg wet tissue. Lake fish tissue
Hg concentrations (mean lake value) range from 18.2 to 771.0 u.g kg"1 ww (Table 2). Mercury
concentration versus the cumulative percentage of lakes is shown in Figure 2. The weighted mean
Hg concentration for these PNW fishable lakes is 144.8 u.g kg^ww
Table 2. Percentiles and lake estimates for mercury concentrations (ug/kgww).
Metric
Mean fish Hgconc. (ug/kgww)
Inference lakes (cumulative no.)
Min.
18.2
13
10th
39.8
84
25th
50.0
220
50th
112.3
451
75th
176.1
650
90th
318.0
807
95th
363.2
853
Max.
771.0
905
Percent of Lakes
95%Conf. Intervals
0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 80C
Mercury Concentration (ug/kg ww)
Figure 2. Cumulative distribution frequency plot of fish tissue Hg by percent of lakes. Red
dashed lines indicate the lake percentile corresponding to three screening values (inferred
population = 905 lakes).
Assessment of Mercury in Fish Tissue
from Pacific Northwest Lakes
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Three screening values, based on variable fish consumption rates, are compared to provide
perspective on the extent of mercury contamination in fish (Table 3, Figure 2). The EPA human
health screening criterion of 300 u.g kg"1 ww was exceeded in an estimated 11% of the fishable
PNW lakes. The most stringent screening value representing high consumers was exceeded in 91%
of the inference lakes.
Table 3. Exceedences of three mercury screening values (inferred population = 905 lakes).
Screening value type
USEPA
General Population
High Consumer
Screen ing value (ug/
kgww)
300
120
40
screening value exceed-
ence (% lakes)
11
44
91
Standard error
4.968
7.634
3.017
C. Comparison to Other Studies
Results are compared to the 2000-2003 nationwide study of contaminants in fish tissue (Stahl et
al. 2009). That study's results were based on a probability sample of 500 lakes stratified by lake
size. Mercury was analyzed from composite fillets using method USEPA1631 (cold-vapor atomic
fluorescence spectrometry). Besides comparing to the nationwide results, comparisons are made
to a subset of this 500 lake dataset representing the predator fish sample data for 28 lakes from
the PNW states of Idaho, Oregon, and Washington. (Herger et al. 2011). Unweighted summary
statistics were calculated for this subset since sample size was small. Summary results for all three
datasets are shown in Table 4.
Table 4. Lake predator fish tissue concentrations of Hg (ug kg'1 ww). Comparison of results to
nationwide and PNW region data from 2000-2003 National Lakes Fish Tissue study.
Study
PNW region-wide 2012-14
Nationwide 2000-03a
PNW region-wide 2000-03b
Mean
144.8
352.0
198.0
Median
112.3
284.6
133.0
Min.
18.2
23.0
23.0
Max.
771.0
6605
601.0
n
50
500
28
Inference pop.
905
36,422
NA
a Stahl et al. 2009.
b Herger et al 2011.
As with the PNW 2012-14 results, mercury was found to be ubiquitous nationwide, present
in all predator samples (Stahl et al. 2009). However, nationwide results had higher mercury
concentrations than the PNW study. The EPA criterion was exceeded in 49% of the inference
population of lakes versus 11% in the PNW lakes. Results presented in this report are more
similar to the PNW subset data from the 2000-2003 study (Table 4). Although not representative
of the entire PNW, this small dataset substantiates our PNW region-wide results. We note two
differences between this 2012-2014 study and the national lakes fish tissue survey: 1) we used a
different tissue mercury analysis method (method 7473 versus method 1631 used in the national
tissue survey) and 2) we used a different trophic guild classification to categorize predator species
affecting two sites (Zaroban et al. 1999).
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The other notable broad-scale study in the PNW is the Idaho state-wide fish tissue toxics study
(Essig and Kosterman 2008). Fish samples from fifty lakes were analyzed for mercury (method
7473) using a probabilistic design, stratified by lake size (> 20 ha). They estimated 29% of a
95 lake inference population exceeded the 300 jig kg"1 ww screening criteria. The sample was
dominated by large lakes, with 40% >120 ha.
D. Feasibility of Fish Tissue as NLA Indicator
The National Lakes Assessment has not included fish tissue toxics because it is an expensive and
time consuming indicator, deemed beyond the scope of the survey. Also, many states have tissue
monitoring as part of their lakes monitoring program so it is not a high priority indicator for all
states. Based on our experience with this study, the following are considerations that may raise the
feasibility of this indicator in future NLA surveys, at least at the regional scale.
Site evaluation: As we did in this assessment, the fish tissue indicator can be limited to fishable
lakes rather than a more robust study (e.g., all lakes population). If this is done, there is a trade-
off in terms of office time versus field time. Sites must be evaluated for fishability to generate the
unbiased target sample, however, field time is more efficient as the resulting set of lakes are known
to have predators so fish collection success rate is higher.
Collection permits: The process of obtaining scientific collection permits is far less complicated
for PNW lakes than for rivers and streams because T&E species are rarely of concern in lakes. We
found conventional methods for catching sportfish in lakes were readily approved by the states.
Fish collection: Angling would be the most efficient predator fish collection method that could
be integrated into the NLA sample day, similar to the methods in the National Coastal Condition
Assessment (USEPA2015). Angling requires minimal gear and is an effective method during
daylight hours. This method is flexible in that can be conducted at various locations during the
sample day (e.g., index site and shoreline access sites).
Fish processing: If the fish tissue indicator is restricted to mercury for human health, only small
amounts of tissue are required. Field procedures could be simplified by collecting tissue plugs
(Peterson et al. 2005), which would reduce field processing time and shipping costs. More analytes
would require processing entire fillets or whole fish.
Assessment of Mercury in Fish Tissue
from Pacific Northwest Lakes
-------
Conclusions
Results of this mercury assessment show that PNW lakes have generally lower fish tissue
mercury concentrations compared to the nation as a whole. However, mercury is ubiquitous in
this PNW aquatic resource and a substantial portion of lakes represented by this survey have
levels of concern for people that are higher consumers offish. These data provide insight into
the general mercury content in lake fish and represents a baseline condition for the PNW. A
trend could be established by repeating this effort in the PNW during future National Lakes
Assessments using similar methods to generate compatible information. This is particularly
relevant for the Western region of the U.S. which is affected by trans-Pacific atmospheric
mercury transport (Huang and Gustin 2012).
This project demonstrates the feasibility of adding fish tissue analysis to the Nation Lakes
Assessment, at least on a regional scale. The level of effort would be similar to the fish
collection effort conducted in the National Coastal Condition Assessment, where angling is
conducted for a set amount of time.
This project was limited to the human endpoint as an indicator of recreation condition of lakes.
Wildlife endpoint would be a useful ecological condition indicator at the regional scale. These
methods could be modified to include relevant species but this would substantially expand
the scope of tissue collection and analysis. Effort to capture a second species and whole fish
processing would be required.
Beyond the overall characterization of the region, these data may be useable as data points
for individual lakes of interest. For example, as a contribution to long-term trend analysis for
lakes known to be elevated in fish tissue mercury (e.g., Phillips Reservoir, OR). For other
lakes in this study, which have never been sampled for fish tissue mercury, these data represent
an initial data point. We encourage those interested to access these data via the EPA WQX
website.
Within the US, the impact of reduced emissions on atmospheric mercury concentrations varies
regionally. While atmospheric mercury concentrations show a decreasing trend nationally,
some Western areas have experienced increasing trends in mercury deposition that may be
attributable to trans-Pacific transport of atmospheric mercury (Weiss-Penzias et al. 2016).
Changes in atmospheric mercury levels can result in changes in fish mercury concentrations
(Harris et al. 2007).The response time can take years and can vary depending on lake and
watershed characteristics. For example, results from several lakes in Mid-Western states that
have been part of long-term monitoring networks have shown that declines in atmospheric
mercury concentrations by -40% over the last decade can be linked to a similar magnitude of
decrease in fish mercury level in some lakes. However, other lakes within the same region have
experienced no trend or even increasing fish mercury concentrations over time, suggesting that
local-scale watershed and lake differences can be critical in affecting the biotic response to
changing atmospheric mercury inputs (Brigham et al. 2014; Hrabik and Watras 2002; Wiener
et al. 2006). These results highlight the complex relationship between fish mercury levels
and atmospheric inputs and underscore the importance offish mercury monitoring efforts to
document the response to changes in local and global mercury emissions.
-------
Acknowledgements
This project was initiated by EPA Region 10 Office of Environmental Assessment. Tony Olsen
and David Peck (EPA-ORD) and Leanne Stahl (EPA-OST) provided advice on the study design.
Chris Eckley (EPA-R10) led the laboratory processing. Information on lakes was provide by
the state National Lakes Assessment coordinators (Shannon Hubler and Leslie Merrick, ODEQ;
Jason Pappani, IDEQ; and Jennifer Wolfe, WDOE). Numerous state fisheries managers were
extremely helpful with answering questions on sample lakes. Region 10 EPA staff support:
Jennifer Crawford, Lorraine Edmond, Gretchen Hayslip, Peter Leinenbach, Theresa McBride,
Brent Richmond, Doc Thompson, Alan Henning, and Leigh Woodruff. Washington Department of
Ecology provided processed fish tissue from Moses Lake (Callie Mathieu). The following people
provided gear and assisted with sampling at several of the lakes:
Colville Indian Tribe: Ed Shallenberger and Brian Keleher
Idaho Department of Fish and Game: Martin Koenig
Oregon Department of Fish and Wildlife: Jeff Ziller, Tim Bailey, Kelly Reis, Eric Moberly, and
Elise Kelley
Washington Department of Ecology: Callie Mathieu
Washington Department of Fish and Wildlife: Danny Garrett and Marc Peterson
Assessment of Mercury in Fish Tissue
from Pacific Northwest Lakes
-------
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-------
Appendix A. Lake sites sampled for fish in Idaho, Oregon, and Washington, 2012-2014.
Year
2013
2013
2013
2013
2013
2013
2013
2013
2013
2013
2013
2013
2013
2013
2013
2013
2014
2014
2014
2014
2014
2014
2014
2014
2014
2014
Site ID
NLA12JD-102
NLA12JD-103
NLA12JD-104
NLA12JD-105
NLA12JD-108
NLA12JD-109
NLA12JD-110
NLA12JD-111
NLA12JD-112
NLA12JD-113
NLA12JD-121
NLA12JD-122
NLA12_ID-141
NLA12JD-143
NLA12JD-145
NLA12JD-148
NLA12JD-151
NLA12_OR-101
NLA12_OR-103
NLA12_OR-105
NLA12_OR-106
NLA12_OR-109
NLA12_OR-110
NLA12_OR-112
NLA12_OR-113
NLA12JDR-123
Site name
Chase Lake
Cave Lake
Treasureton Res.
Shepherd Lake
Killarney Lake
LakeWalcott
Carey Lake
Cedar Creek Res.
Perkins Lake
Otter Pond
Lake San Souci
Chesterfield Res.
Sage Hen Res.
Shoofly Res.
Bull Trout Lake
Waha Lake
Thorn Creek Res.
Mann Lake
Sparks Lake
Phillips Res.
Smith Res.
Waldo Lake
Cooper Creek Res.
Beulah Res.
Emigrant Lake
Keen Creek Diversion
Pond
Latitude (DD)
48.457702
47.457299
42.234223
48.184540
47.517242
42.677045
43.317614
42.210602
48.756681
44.838471
48.007041
42.895254
44.329039
42.264258
44.299952
46.201006
43.190822
42.772825
44.023822
44.681223
44.313141
43.731777
43.378746
43.932778
42.157825
42.130013
Longitude (DD)
-116.824065
-116.599627
-111.852058
-116.527585
-116.565414
-113.407296
-113.921339
-114.893838
-116.092672
-116.036701
-117.003441
-111.963806
-116.185324
-116.310496
-115.254295
-116.834907
-114.595021
-118.447257
-121.744618
-118.047442
-122.045427
-122.039771
-123.270434
-118.149981
-122.607634
-122.478277
St.
ID
ID
ID
ID
ID
ID
ID
ID
ID
ID
ID
ID
ID
ID
ID
ID
ID
OR
OR
OR
OR
OR
OR
OR
OR
OR
County
Bonner
Kootenai
Franklin
Bonner
Kootenai
cassia
Blaine
Twin Falls
Boundary
Valley
Bonner
Caribou
Gem
Owyhee
Boise
Lewis
camas
HARNEY
DESCHUTES
BAKER
LINN
LANE
DOUGLAS
MALHEUR
JACKSON
JACKSON
Area (HA)
70.5
399.6
61.5
39.3
201.8
3395.5
81.8
393.0
21.5
9.7
12.7
504.2
71.6
35.5
27.9
38.1
44.6
89.8
128.1
911.8
63.7
2443.7
52.7
716.8
256.5
4.4
Elev.
(M)
761
649
1512
695
647
1279
1452
1593
803
1520
706
1646
1507
1690
2117
1034
1679
1272
1656
1242
795
1652
207
1019
684
1344
Species type
Non-salmonid
Non-salmonid
Both
Non-salmonid
Non-salmonid
Non-salmonid
Non-salmonid
Salmonid
Non-salmonid
Non-salmonid
Non-salmonid
Salmonid
Salmonid
Salmonid
Salmonid
Both
Salmonid
Salmonid
Salmonid
Non-salmonid
Salmonid
Salmonid
Non-salmonid
Salmonid
Non-salmonid
Salmonid
Total
fish
10
6
12
13
4
9
10
5
10
10
11
7
8
12
10
25
1
10
18
10
14
10
5
3
10
5
Design
weight
17.074
18.801
15.837
46.240
20.890
17.439
15.837
17.439
3.292
12.111
22.876
5.358
5.358
3.292
3.292
3.292
3.292
13.532
39.510
16.065
14.589
11.788
14.589
16.065
16.065
24.668
-------
Appendix A continued. Lake sites sampled for fish in Idaho, Oregon, and Washington, 2012-2014.
Year
2014
2014
2014
2014
2014
2014
2014
2012
2012
2012
2012
2012
2012
2012
2012
2012
2012
2012
2012
2012
2012
2012
2012
2012
Site ID
NLA12JDR-126
NLA12JDR-128
NLA12JDR-129
NLA12JDR-145
NLA12JDR-154
NLA12JDR-155
NLA12JDR-167
NLA12_WA-101
NLA12_WA-103
NLA12_WA-104
NLA12_WA-106
NLA12_WA-107
NLA12_WA-108
NLA12_WA-111
NLA12_WA-115
NLA12_WA-116
NLA12_WA-118
NLA12_WA-120
NLA12_WA-121
NLA12_WA-124
NLA12_WA-126
NLA12_WA-133
NLA12_WA-138
NLA12_WA-141
Site name
Fish Lake
Odell Lake
Carter Lake
Beale Lake
Malheur Res.
Agate Res.
Sunset Lake
Island Lake
American Lake
Moses Lake
Swofford Pond
Lacamas Lake
Sacheen Lake
Wapato Lake
Summit Lake
Upper Goose Lake
Ravensdale Lake
Round Lake
Martha Lake
McGinnis Lake
North Skookum Lake
Sportsmans Lake
Phantom Lake
Bay Lake
Latitude (DD)
44.833708
43.574485
43.854166
43.506883
44.362642
42.407265
46.097165
46.427311
47.126413
47.076941
46.497536
45.616388
48.153953
47.918921
48.959237
46.941005
47.350898
48.292275
47.852997
48.036518
48.405734
48.568425
47.593387
47.243816
Longitude (DD)
-121.813775
-122.006858
-124.146755
-124.234262
-117.693932
-122.767691
-123.928461
-124.035559
-122.562583
-119.324822
-122.405060
-122.425707
-117.318529
-120.165112
-118.127192
-119.279312
-121.992564
-118.322820
-122.242745
-118.891997
-117.178410
-123.073521
-122.124337
-122.757955
St.
OR
OR
OR
OR
OR
OR
OR
WA
WA
WA
WA
WA
WA
WA
WA
WA
WA
WA
WA
WA
WA
WA
WA
WA
County
Marion
KLAMATH
DOUGLAS
COOS
MALHEUR
JACKSON
Clatsop
Pacific
Pierce
Grant
Lewis
Clark
Pend Oreille
Chelan
Stevens
Grant
King
Ferry
Snohomish
Okanogan
Pend Oreille
San Juan
King
Pierce
Area (HA)
14.7
1389.8
13.4
45.0
202.4
70.6
15.0
17.6
441.5
2575.6
84.0
101.3
120.4
76.7
4.1
53.1
6.4
20.6
22.6
48.1
16.2
26.4
24.0
49.7
Elev.
(M)
1300
1460
19
12
1027
461
8
7
73
320
239
56
682
376
774
264
181
692
140
730
1092
48
78
10
Species types
Salmonid
Salmonid
Salmonid
Non-salmonid
Salmonid
Non-salmonid
Non-salmonid
Non-salmonid
Non-salmonid
Non-salmonid
Non-salmonid
Non-salmonid
Non-salmonid
Non-salmonid
Salmonid
Both
Salmonid
Salmonid
Non-salmonid
Salmonid
Salmonid
Non-salmonid
Non-salmonid
Non-salmonid
Total
fish
6
11
10
7
13
6
9
3
10
18
9
5
10
11
6
13
2
24
9
22
6
9
4
10
Design
weight
13.167
17.032
13.167
10.553
17.032
17.032
13.167
92.239
6.623
6.623
22.496
24.771
24.771
20.866
39.673
16.402
39.673
15.386
15.386
15.386
18.321
15.386
15.386
15.386
-------
Appendix B. List of species targeted for lake fish tissue sampling based on likely
sportfish species present in sample lakes.
Family
Centrarchidae
Ictaluridae
Percidae
Salmonidae
Scientific name
Micropterus dolomieu
Micropterus salmoides
Pomoxis nigromaculatus
Pomoxis annularis
Ambloplites rupestris
Lepomis macrochirus
Lepomis gibbosus
Lepomis cyanellus
Ameiurus nebulosus
Perca flavescens
Sander vitreus
Oncorhynchus nerka
Salvelinus namaycush
Oncorhynchus mykiss
Oncorhynchus clarkia
Salvelinus fontinalis
Sal mo trutta
Prosopium Williamson!
Common name
smallmouth bass
largemouth bass
black crappie
white crappie
rock bass
bluegill
pumpkin seed
green sunfish
brown bullhead
yellow perch
walleye
kokanee
lake trout
rainbow trout
cutthroat trout
brook trout
brown trout
mountain whitefish
Adult feeding strategy
Piscivore
Piscivore
Invert/piscivore
Invert/piscivore
Invert/piscivore
Invert/piscivore
Invert/piscivore
Invert/piscivore
Invert/piscivore
Invert/piscivore
Piscivore
Invertivore
Piscivore
Invert/piscivore
Invert/piscivore
Invert/piscivore
Invert/piscivore
Invertivore
General Igth range
(in)
6-15
8-20
6-14
6-14
6-10
4-8
4-8
4-8
6-10
6-11
10-24
8-15
14-28
8-14
8-14
6-14
10-16
8-14
" Includes subspecies that occur in the PNW.
b Based on Zaroban et al. 1999.
Assessment of Mercury in Fish Tissue
from Pacific Northwest Lakes
-------
©EPA
United States
Environmental Protection
Agency
Region 10
1200 Sixth Avenue, Suite 900
Seattle, WA 98101-1128
------- |