Sample Sites
Sample sites represent areas that are downstream of former
placer mining activities, and also non-mining areas for control
and comparison purposes (Figure 1). A discrepancy between creek
names was found on the USGS Nulato (B-4) Quadrangle map and a map
used for a trapping pattern study by the Alaska Department of
Fish and Game (ADF&G) Subsistence Division (Robert 1984).
Bonanza Creek on the USGS Nulato (B-4) Quadrangle map originates
in the Camp Creek drainage. It appears that Bonanza Creek is
correctly labeled as Camp Creek on the ADF&G map. USFWS has
referred to this sample site as Bonanza Creek, sample site 5
(Snyder-
Figure 1. Map of sample sites within the Kaiyuh Flats study
area.
#3 Bishop Creek
#5 Camp Creek
#11 Bonanza Creek
#12 North Creek/American Creek
#13 Yukon Creek
Conn et al 1992b). Eddy Creek on the USGS Nulato (B-4)
Quadrangle map is renamed as Bonanza Creek on the ADF&G map.
North Creek is renamed American Creek on the ADF&G map at
approximately Township 13S, Range 5E, and Section 4, SW 1/4. The
ADF&G map, because it is consistent with the local knowledge
and place names of the area, was used for this study. Description
of sites in Figure 1 are as follows:
Site 3. Bishop Creek. USGS Nulato (C-3) Quadrangle. Township 9S, Range 8E, Section 35. Water samples collected. No fish captured in this drainage.
Site 5. Camp Creek. USGS Nulato (B-4) Quadrangle. Township
12S, Range 6E, Section 17, NE 1/4. Water and fish were collected
immediately below the fork of Camp Creek in the NE 1/4 of Section
17.
Site 11. Bonanza Creek. USGS Nulato (B-4) Quadrangle. Township
12S, Range 5E, Section 35, NE 1/4. Water samples were collected
in Section 35, NE 1/4. Fish were captured from Bonanza Creek
within Sections 35 and 26.
Site 12. North Creek. USGS Nulato (B-4) Quadrangle. Township
13S, Range 5E, Section 9, NW 1/4. Water samples collected.
Site 12A. American Creek. USGS Nulato (B-4) Quadrangle.
Township 12S, Range 5E, Section 30, SW 1/4. Fish captured.
Site 13. Yukon Creek. USGS Nulato (B-5) Quadrangle. Township
13S, Range 3E, Section 3, NW 1/4. Water samples and fish were
collected within Yukon Creek immediately before the confluence
with 22-Mile Slough (Khotol River).
All field work and sampling was conducted between 23-27
August, 1993. Of the five separate drainages sampled, Camp Creek
has a history of gold placer mining, and Bishop Creek has a
history of lead-silver production. North/American Creek, Bonanza
Creek, and Yukon Creek have no documented mining history.
Permits applied for and received for this project included: 1)
a conditional State of Alaska Department of Fish and Game
Scientific Permit for collecting fish with a gill net, and 2) a
conditional United States Department of the Interior Fish and
Wildlife Service Refuge Special Use Permit.
A unique identification number was given to each fish captured
and each water sample collected. The system used for this project
is based on a system used by the USFWS within the Northern Unit
of the Innoko National Wildlife Refuge. The identification number
describes the area, sample site number, type of sample, sample
number, and type of tissue. An example for a fish tissue sample
would be as follows: NIN05PO01M, where NIN is the Northern Unit
of the Innoko National Wildlife Refuge, 05 is the sample site, P
is northern pike, 001 is sample number, and M is muscle tissue.
An example for a surface water sample would be as follows: NIN 11
H2O 01, where NIN is the Northern Unit of the Innoko National
Wildlife Refuge, 11 is the sample site, H20 is a surface water
sample, and 01 is the sample number.
Surface Water
Surface water grab samples were collected at each site using
500 ml Nalgeneâ bottles just below
the water surface and upstream of the collector. At the time
surface water samples were collected, surface water temperature (° C) was recorded using a hand-held alcohol
thermometer. pH was recorded using a Whatman model PHA300
portable pH meter. The meter was calibrated before each
measurement with standard buffer solutions of pH 4.01 and pH
7.01. Water samples were chilled on blue ice and brought back
from the field for analysis of turbidity, hardness, and
conductivity. A duplicate surface water grab sample was collected
at each site using a 500 ml plastic bottle provided by Columbia
Analytical Services (CAS). The bottle contained nitric acid for
the purpose of fixing the water sample to a pH of less than 2.0. The
duplicate sample was shipped to CAS in for metals analyses.
Turbidity was measured in nephelometer turbidity units (NTU)
using a Hach Portable Turbidimeter Model 2100P, calibrated with
Hach Gelex secondary standards for 1, 10, and 100 NTU. Hardness
was measured in parts per million (ppm) of calcium carbonate
(CaCO3) using Hach hardness and digital titration
methods and color endpoints. Conductivity was measured in umhos/cm
using a Hach DREL/5â Conductivity
meter with automatic temperature compensation. The USFWS
Ecological Services, Fairbanks, provided the instruments for
these measurements.
Fish
Fish were captured using conventional hook and line
techniques. The target number of twelve (12) northern pike (Esox
lucius) captured per sample site was achieved at four (4) of
the five (5) sample sites for a total sample size of forty eight
(48) specimens. Although effort was put forth, no fish were
captured at Bishop Creek.
Total length (mm), fork length (mm), and weight (grams) were
recorded for each fish prior to field dissection. Weight was
measured using either a 2 kg, 5 kg, or 15 kg Chatillon hand-held
scale. After fish metrics were recorded for each specimen, the
same specimen was placed on a polyethylene dissection board that
was pre rinsed with distilled water. Upon dissection, skin-off
dorsal muscle tissue was removed from the right side of the
specimen using a sterile stainless steel scalpel blade. The
tissue sample was then placed into a new 125 ml plastic bottle
and sealed. The corresponding identification number was recorded
into a field notebook and written in permanent ink on the bottle.
Each bottle was placed into a cooler with blue ice.
After each tissue sample was collected, the sex of each fish
was recorded along with a cursory stomach content analysis.
Scales and vertebrae were collected from each specimen for age
analysis. Aging of vertebrae and scales was performed by the
ADF&G Sportfish Division, Fairbanks, AK.
Prior to dissection of the next specimen, the dissection board
was rinsed with distilled water and wiped dry with a disposable
paper towel. A new sterile stainless steel scalpel blade was used
for each tissue sample removed. A new pair of talc-free plastic
surgical gloves was used when handling and dissecting each
specimen.
Aware that livers, kidneys, intestines, and sex organs are
routinely consumed by Kaiyuh Flats area residents, dorsal muscle
was chosen for metals analysis due to the much greater amount of
edible tissue provided per fish. The fact that individual body
organs, such as the liver, may contain higher or lessor
concentrations of contaminants is noted.
Upon return to Fairbanks, dry ice was placed in each cooler
and the tissue and water samples were sent to Columbia Analytical
Services (CAS) in Kelso, Washington for analysis of total mercury
and total selenium.
Quality Assurance/ Quality Control (QA/QC)
Methods used by Columbia Analytical Services (CAS) for total
mercury and selenium analyses were cold vapor atomic absorption,
and graphite furnace atomic absorption, respectively. EPA methods
used for analysis of total mercury and selenium in water samples
were #7470 and #7740, respectively. EPA methods used for analysis
of total mercury and selenium in fish tissues were #7471 and
#7740, respectively. Total mercury analysis of surface water
samples was completed within the required 28-day holding time
(APHA et al. 1989).
Quality control screening used by CAS resulted in acceptable
precision and accuracy for each metal analyzed in both fish
tissue and water samples. The laboratory tested duplicate samples
for relative percent difference (RPD), spiked duplicate samples
for percent spike recovery, and analysis of standard reference
materials (commercially provided tissue of known metal
concentration). Therefore, the confidence level is high for the
validity of the analysis results. The QA/QC laboratory report is
presented in Appendix B.
Surface Water
Results of analysis for total metals concentration in surface
water at each sample site were below the minimum limit of
detection (LOD) of 0.0002 ppm for mercury, and 0.005 ppm for
Selenium. Therefore, results of each sample analysis are reported
as not detectable (ND) in Table 2.
For all sample sites, surface water temperatures ranged from
6.5° C to 11.0°
C, (mean= 8.5° C). pH ranged from
6.85 to 8.08, (median= 7.68). Turbidity ranged from 0.31 NTU to
1.23 NTU (mean= 0.77 NTU). Conductivity ranged from 62 umhos/cm
to 260 umhos/cm (mean= 141.4 umhos/cm). Hardness
ranged from 27 ppm CaCO3 to 152 ppm CaCO3
(mean= 73.4 ppm). Water quality data is presented in Table 1.
Fish
Results of fish body size, age at capture, and metal
concentrations of the muscle tissues collected are presented in
Table 2. Fork length (FL) of fish captured ranged from 301 mm to
1010 mm (mean= 625). A length frequency of fish captured is
presented in Table 3. All fish captured were sampled. Age of fish
based on vertebrae aging ranged from 2 years to 19 years of age
(mean= 6.8 years). Weight of fish ranged from 250 grams to 7000
grams (mean= 2130 grams). Twenty-five (25) males and twenty-three
(23) females were captured resulting in a male to female ratio of
1.1:1.
All muscle tissue samples analyzed were above the LOD of 0.005
ppm for total mercury, but below the LOD of 0.400 ppm for total
selenium. Total mercury in muscle tissue ranged from 0.091 ppm
wet weight to 0.832 ppm wet weight (mean= 0.438 ppm). Columbia
Analytical Services (CAS) analytical report is presented in
Appendix A. CAS reported the metals concentrations in both wet
weight (as received) and dry weight. The dry weight values can be
converted to wet weight by using equation 1:
% Freeze Dried Solids
ppm Wet Weight 100 x ppm Dry Weight
Equation 1.
For all sample sites combined, concentrations of total mercury
in muscle tissue show a strong positive correlation when
plotted against the total length of the fish (Figure 2). The
Pearson correlation coefficient is r=0.816.
Fish from the Camp Creek sample site, the creek where upstream
gold placer mining had occurred, had a Pearson correlation
coefficient of r=0.873 when mercury in fish tissue was plotted
against the fork length of the fish. The remaining three
drainages sampled, where no documented mining has taken place,
resulted in the following Pearson correlation coefficients: North
Creek/American Creek r=0.918, Bonanza Creek r=0.617, and Yukon
Creek r=0.707.
For all sample sites combined, plotting the age of fish
against the total mercury concentrations in fish tissues results
in a strong positive correlation. The Pearson correlation
coefficient is r=0.737. Total mercury plotted vs. age of fish is
presented in Figure 3.
Water
Results from all water quality parameters sampled were within
the Alaska Water Quality Standards 18 AAC 70. The low turbidity
levels for Camp Creek and Bishop Creek suggest little or no
physical water quality degradation, suspension, or resuspension
of sediments, at least downstream to the sample sites was
occurring. This may be directly related to the fact that no
placer or lode mining activities were taking place during the
sample period.
The absence of mercury and selenium being detected in surface
waters is not necessarily surprising. Similar research has shown
that while total mercury and selenium are below detection limits
in surface waters, these same metals were above detection limits
in fish muscle tissue (Speyer, 1980). The USFWS has data for two
sites sampled within this study and also show mercury to be below
detection limits in surface waters while fish tissues contained
detectable amounts. The two sites sampled by USFWS in the study
area were Bishop Creek and Camp Creek (Snyder-Conn et. al,
1992b).
Fish
All fish sampled, regardless of sample site, had mercury
concentrations above method detection limits. This is consistent
with preliminary results from a recent USFWS draft technical
report for thirty-one (31) northern pike sampled at ten (10)
sites within three national wildlife refuges in the area. For the
Kaiyuh Flats total mercury wet weight muscle tissue
concentrations reported for twelve (12) northern pike (assuming
25% freeze dried solids) ranged from 0.205 ppm to 0.563 ppm
(mean= 0.403 ppm). Kidney and liver tissue also were analyzed for
each specimen (Mueller et al. 1995).
Each individual sample site within this project has a strong
positive correlation when Hg is plotted vs. fork length of fish
and age of fish. These strong positive correlations are
indicative of bioaccumulation (uptake via gills and skin) and
biomagnification (food chain transfer) of mercury within the
aquatic system. No specific sample site within the Kaiyuh Flats
appeared to have fish with a significantly higher amount of
mercury when correlated to fish size and fish age. Rather,
mercury concentrations in fish muscle tissue appear to be
ubiquitous.
The possibility of mercury accumulation as a result of
off-refuge movements by northern pike was initially considered.
During 1994 and 1995 the USFWS Fishery Resource Office,
Fairbanks, AK and the ADF&G, Sportfish Division, Fairbanks,
AK monitored northern pike movements in the Kaiyuh Flats using
radio telemetry techniques. No off-refuge movements of northern
pike were observed (Lubinski, USFWS, pers. comm.). It is unlikely
that any off-refuge movements by northern pike are a contributing
factor to on-refuge fish tissue mercury concentrations. Although,
additional information on prey (whitefish) movements would assist
in determining contributions to the mercury body burden of
on-refuge northern pike.
Erosion of natural mercury deposits may be a source of mercury
to the Kaiyuh Flats, but it appears that there are no documented
cinnabar (HgS) deposits that could weather and drain into the
Kaiyuh Flats catchment basin (Cruz and Cobb, 1984). Therefore,
atmospheric deposition of mercury should be considered as a
possible source of mercury to the Kaiyuh Flats.
Selenium concentrations in pike tissue were all below the LOD
of 0.400 ppm wet weight. These results suggest that selenium may
be present in insufficient quantities within the aquatic and
biotic systems to potentially counteract the adverse effects of
methylmercury. However, Mueller et al. (1995) reports selenium to
be above detection limits of 0.500 ppm (reported as dry weight)
in muscle, tissue, liver tissue, and whole body samples of all
pike captured within the Kaiyuh Flats. After conversion to wet
weight, the mean concentration for selenium in muscle tissue is
0.254 ppm wet weight, and the mean concentrations of mercury and
selenium appear to be in a 1.6:1 ratio. The reason for this
discrepancy is not known at this time, but could be a function of
the relatively high method reporting limit of 0.400 ppm as
reported by CAS. One researcher offered that the majority of
selenium present in the specimens collected may have been
concentrated in the liver and still provided an antagonistic
effect on the mercury present in muscle tissue (P.
Weber-Scannell, ADF&G, pers. comm. 1996).
Comparing the mercury concentrations in fish tissue from this
project to guidelines used by the Minnesota Department of Health
(Schubat 1990), the concentrations are considered to be low to
moderate. However, all results of northern pike sampled for total
mercury concentrations fell below the 1.0 ppm Food and Drug
Administration (FDA) action level for consumption advisories.
Using the least squares method to calculate a straight line
for mercury plotted against fork length results in the linear
equation Y= -0.1662 + 0.00097 X. Mean length-at-age data from 925
northern pike captured from the Kaiyuh Flats during a
USFWS/ADF&G 1994 radio telemetry project resulted in a fork
length modal peak (n=161) at 642 mm and a maximum fork length of
1160 mm (Taube 1995). Substituting 642 mm and 1160 mm for X in
the linear equation and solving for Y, results in calculated
mercury concentrations of 0.457 ppm and 0.959 ppm, respectively.
Therefore, based on the linear equation derived from this
project, the largest specimen from a sample size of 1004 northern
pike [48 fish from this project, 31 from Mueller, et al. (1995),
and 925 from the USFWS/ADF&G 1994 project] does not exceed
the 1.0 ppm FDA action level.
Fish Consumption and Risk Assessment
Several states have issued fish consumption advisories
concerning specific species with elevated concentrations of
mercury. At this time the State of Alaska has no advisories for
fish consumption in marine or fresh waters. FDA action levels are
essential on a national and inter-state basis, but may not be
appropriate for local and site-specific situations where more
definitive information is available.
An example of using results from this project in a fish
consumption advisory model would be as follows: If the average
size of fish that are harvested is 625 mm (È
25 inches), the calculated concentration of mercury in muscle
tissue (based on the linear equation of Y= -.1662 + 0.00097 X)
would be 0.440 ppm. Using this 0.440 ppm value in a model
(Equation 2) proposed by Dourson and Clark (1990), the
recommended amount of fish muscle tissue to be consumed over a
year-long period without any adverse health effects would be
approximately 17.4 kilograms (38.3 lbs). This advised amount of
consumption is calculated for an adult male whose body weight is
70 kg (I 54 lbs.).
RfD (mg of chemical/kg bw/day) X 70 (kg bw)
Fish intake (kg of fish/day)= fish concentration (mg of
chemical/kg of fish)
Equation 2. Where reference dose (RfD) for mercury is 3 E-4
and (bw) is body weight.
Schubat (1991) recommends that sensitive individuals (pregnant
women, nursing mothers, and children under six (6) years of age)
consume only 25% of this amount, therefore reducing the
recommended amount of consumption to approximately 4.4 kg. (9.6
lbs.) per year. Table 3 presents various fish sizes, calculated
mercury concentrations, and recommended consumption amounts based
on Shubat (1991) and Dourson and Clark (1990).
It should be noted that the Minnesota Department of Public
Health has classified fish consumers as either long term
(chronic), 3-12 months/year, and short term (acute), 3
months/year or less. Long term more consistent exposure poses
more of a concern because as the period of exposure increases the
adverse effect concentration (ppm) decreases. Nearly all of the
RfDs are based on long-term daily exposure, therefore,
incorporating a more conservative approach into fish advisory
models. Based on models proposed by Shubat (1991), it would be
safe to chronically consume 2.8 meals/month of fish containing
1.0 ppm. In this case 1 meal would be considered 0.5 lbs.
The reader should be aware of the considerable debate and
dissatisfaction among scientists, health care professionals,
regulators, and ordinary citizens regarding human health risk
assessment associated with mercury in the environment (Graham
1995). The fish consumption models described above use reference
doses (RfD) within their respective equations. A RfD is an
estimate of daily exposure of the human population to mercury
that would not result in an appreciable risk of deleterious
effects during a lifetime. However, new approaches are being
explored using a "benchmark" approach to more
accurately estimate RfDs. The "benchmark" approach
utilizes all data points in a set rather than relying on
individual data points for RfD estimation.
Depending on an individual's fish consumption habits, level of
consumption, and body weight, the recommended consumption levels
will vary. Due to the lack of published data on actual
consumption rates for the residents of the villages of Kaltag,
Nulato, and Koyukuk, estimates of consumption rates are variable
and are based on personal communication.
Area residents continue to use the Kaiyuh Flats area for
numerous subsistence activities. Northern pike are generally
harvested using hook and line techniques. Pike are eaten on site
and/or brought back to the villages for human consumption as well
as dog food. Northern pike are prepared for consumption in
various ways, including: head off and boiled, fried guts (cleaned
intestines), livers, kidneys, and gonads, and boiled and made
into "ice cream." "Ice cream" is a
combination of boiled pike muscle tissue, moose fat, and berries.
The mixture is frozen and usually eaten within two weeks.
Although some area residents regularly harvest and consume
northern pike, there are still concerns of elevated mercury
concentrations in the fish. As a result, there is a general
feeling that the larger fish should not be eaten. Additionally,
it is difficult to quantify the amount of fish harvested and
consumed on a yearly basis (G. Yaska and C. Peter, pers. comm.
1995).
Subsistence harvests of northern pike by Galena area residents
during 1985 and 1986 have been reported by the ADF&G as 5.2
pounds of edible fish per capita (Marcotte 1990). This report
does not describe the area of harvest, therefore, an unquantified
amount of the northern pike may have been harvested from the
Yukon River mainstem.
Possible comparisons may be made between the villages of
Kaltag and Nulato to other villages in interior Alaska that are
located in similar basin settings. The villages of Huslia and
Minto are each situated in lake/river regions and residents fish
for pike in open water and through the ice. Values for edible
pounds of pike harvested per capita for Huslia was 28.8 pounds in
1983, and 76.7 pounds for Minto in 1984 as reported by the
ADF&G (Walker et al. 1988). These reported values represent
the edible pounds of pike harvested. The need for further
research on actual pounds of fish consumed on a per capita basis
must be stressed.
RECOMMENDATIONS
1) It is the recommendation of TCC's Wildlife &
Parks Program that results from this project be used by the State
of Alaska Department of Health and Social Services, Division of
Public Health, to determine whether guidelines are needed
concerning consumption rates of northern pike harvested within
the study area. Concern remains regarding recommended consumption
of fish by sensitive individuals (pregnant women, nursing
mothers, and children under six (6) years of age).
2) Additional information should be gathered regarding actual
amounts of fish consumed per capita by Kaiyuh Flats area
residents.
3) Due to potential hard rock mining activities proposed for
the Kaiyuh Mountains, periodic heavy metals information should be
gathered from sediment, water, and fish tissue within the Kaiyuh
Flats area.
Go to References