Total mercury concentration in fish tissue relative to length and weight
David M. Snyder1, Colleen R. Parker1, Yokota Kiyoko1
ABSTRACT
A 2011 Fish Advisory published by the New York State Department of Health listed
several lakes and rivers in Central New York as a concern for mercury. Goodyear Lake in
Otsego County was among these waters. Children and women of childbearing age were advised
to not consume any of the fish listed, and men should limit their intake to 4 meals per month. As
a baseline study, we chose to investigate how mercury is accumulating in fish tissue, based on
fish species, length and weight in Goodyear Lake. Fish tissue samples were collected from
walleye, yellow perch, smallmouth bass, and largemouth bass, and were sent to Syracuse
University Lab for mercury analysis. All 29 fish tissue samples were above the New York State
Environmental Protection Agency mercury limit of 0.30 ng/Kg. Four of these samples were
above the intolerable limit of 1.00 ng/Kg for consumption. We are currently investigating if these
values show any trends based on species, length and weight, and are hoping to collect more fish
tissue from Goodyear and other lakes in the future.
INTRODUCTION
In recent years, mercury (Hg) levels in freshwater ecosystems have increased to a point
that fish advisories, documentation of which water bodies are affected and to what extent, are
placed on freshwater bodies in United States. The main contributor of Hg pollution into today’s
environment is anthropocentric (Taylor et al. 2014). As Hg is precipitated from the atmosphere,
it enters waterways where it often starts its transformation from Hg to methyl mercury (MeHg)
(Taylor et al. 2014). Hg is converted to the more toxic and organic form, MeHg, by bacterialmediated process (Gilmour et al. 1992). MeHg, considered a neurotoxin, enters the aquatic
environment and is bio-magnifies through the food web. By the time humans consume fish, the
concentrations of MeHg is considered harmful (UNEP 2013).
We looked at the levels of MeHg in water and soil concentrations from Goodyear Lake
(Figure 1) and various locations in the upper Susquehanna River. Fortunately, all locations
tested for MeHg, in water were under the United States Environmental Protection Agency
(USEPA) detection limits for MeHg (0.02 ng/L) when no background elements or interferences
were present (USEPA 1998). As well, Hg in soil concentrations were all under EPA detection
limits for MeHg, 5 µg/kg (USEPA 2003).
A New York State Department of Health (NYSDOH) report, in 2014 on Chemicals in
Sportfish and Game Species, placed a fish consumption advisory on Central New York
(NYSDOH 2014). Goodyear Lake, Otsego County, New York was listed as having elevated
levels of MeHg in its fish. The advisory stated that, because of the high levels of MeHg, males
should only consume approximately one fish per week, and women, of child bearing age, should
not consume fish at all (NYSDOH 2014).
The aim of this study was to find Hg concentrations in fish, and to test the effect of length
and the effect of weight on concentrations of MgHg in fish from Goodyear Lake, Otsego County,
New York (Figure 1).
METHODS
We collected four fish species (n=28) (Table 1), in April of 2014, from Goodyear Lake.
Within Goodyear Lake, we set up three fish traps in different intake channels. We recorded the
length and weight of each fish.
We collected fillets which were analyzed by Syracuse University for analysis (USEPA
1998). Syracuse University performed a Direct Mercury Analyzer (EPA method 7473A) and
recorded the total mercury value for each sample (USEPA 1998). We analyzed tissue for total
Hg (THg) based on the Simonin et al. study (2008) which found that 95% of the Mg in fish is
MeHg. Since 95% of the Mg in fish is MeHg, we use THg as a substitute (Simonin et al. 2008).
We collected samples of Micropterus salmoides, Micropterus dolomieu, Perca flavescens, and
Sander vitreus.
B
C
A
Figure 1. Map of Goodyear Lake, Otsego County, NY. (A) site 1, (B) site 2, and (C) site 3
(Google Maps).
RESULTS
Table 1 provides the mean weight and length for each species collected. Figure 2
provides the THg for each species. Of the samples, four were found to be above 1.0 µl/L. Of the
four samples that were above the 1.0 µl/L, 50% were S. vitreus and the other 50% were M.
dolomieu.
Table 1. Summary statistics for fish collected from Goodyear Lake, 2014. N – number of composite
fish sample analyzed in study.
Figure 2 shows us that 100% of the samples are above the United States Environmental
Protection Agency’s fish criterion level of 0.3 µl/L (NYSDOH 2014). As well, we found that
14% of our samples were above the United States Food and Drug Administration action level of
1 µl/L (USFDA 1995). Our data support the NYSDEC’s implementation of the advisory on
Goodyear Lake. As well, we also advise that males only eat four fish a month, and women,
especially of childbearing age, shouldn’t consume fish from Goodyear Lake. We also found a
positive correlation between weight and Hg levels and between length and Hg. We attribute
these two correlations to the bio-accumulation potential of older fish. An increase in the length
and/or weight has shown to correlate with the age of the fish. We could conclude that the older
the fish, the higher bio-accumulation potential of Hg.
USFDA
Action
level (1
µl/L)
USEPA
fish
criterion
level (0.3
µl/L)
Figure 2. Mean concentrations of Hg/g relative to fish species. Error bars are +/- 1 standard.
Unfortunately, we had problems that could have affected our data. The first problem was
inadequate sample size. Due to our limited budget we could only assess 28 fish, and that sample
size was insufficient. Another problem was that the weight of some fish was higher than
expected. We attribute the inconsistency in weights to a mix of spawned and un-spawned females. At
the time we took our samples, it was spawning season, and, due to the added weight of the eggs, the
mass of female fish was often elevated.
We recommend increased funding to allow for a statistically significant sample size. To
reduce the effect eggs had on the weight of the fish, we recommend collecting samples after the
spawning period. We further recommend an examination of gut contents to determine if fish dietary
patterns of have an effect on Hg content.
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