Optimizing fish sampling for fish–mercury bioaccumulation factors (original) (raw)
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Optimizing Stream Water Mercury Sampling for Calculation of Fish Bioaccumulation Factors
Environmental Science & Technology, 2013
Mercury (Hg) bioaccumulation factors (BAFs) for game fishes are widely employed for monitoring, assessment, and regulatory purposes. Mercury BAFs are calculated as the fish Hg concentration (Hg fish ) divided by the water Hg concentration (Hg water ) and, consequently, are sensitive to sampling and analysis artifacts for fish and water. We evaluated the influence of water sample timing, filtration, and mercury species on the modeled relation between game fish and water mercury concentrations across 11 streams and rivers in five states in order to identify optimum Hg water sampling approaches. Each model included fish trophic position, to account for a wide range of species collected among sites, and flow-weighted Hg water estimates. Models were evaluated for parsimony, using Akaike's Information Criterion. Better models included filtered water methylmercury (FMeHg) or unfiltered water methylmercury (UMeHg), whereas filtered total mercury did not meet parsimony requirements. Models including mean annual FMeHg were superior to those with mean FMeHg calculated over shorter time periods throughout the year. FMeHg models including metrics of high concentrations (80th percentile and above) observed during the year performed better, in general. These higher concentrations occurred most often during the growing season at all sites. Streamflow was significantly related to the probability of achieving higher concentrations during the growing season at six sites, but the direction of influence varied among sites. These findings indicate that streamwater Hg collection can be optimized by evaluating site-specific FMeHg − UMeHg relations, intra-annual temporal variation in their concentrations, and streamflow-Hg dynamics.
Canadian Journal of Fisheries and Aquatic Sciences, 2013
Fish mercury (Hg) concentrations have been measured over the last 30-40 years in all regions of Canada as part of various monitoring and research programs. Despite this large amount of data, only regional assessments of fish Hg trends and patterns have previously been attempted. The objective of this study was to assemble available freshwater fish Hg concentration data from all provinces and territories and identify national patterns. The Canadian Fish Mercury Database includes over 330 000 records representing 104 species of freshwater fish collected from over 5000 locations across Canada between 1967 and 2010. Analysis of the 28 most frequently occurring species (>1000 records) showed that the majority of variation in Hg concentrations (when normalized to a standard size) was accounted for by geographic location. Median Hg concentrations increased with trophic level (r = 0.40, p < 0.05), with the highest Hg concentrations found in piscivorous species such as walleye (Sander vitreus), northern pike (Esox lucius), and lake trout (Salvelinus namaycush). The Canadian Fish Mercury Database provides the most comprehensive summary of fish Hg measurements in Canada, and the results indicate that several regionally observed trends in fish Hg concentrations (e.g., Hg biomagnification and geographic variation) are observed at a national scale. Implications for the effective assessment of changes in fish Hg concentrations in relation to changes in Hg emission regulations are discussed.
Total mercury in wild fish in Guizhou reservoirs, China
Journal of Environmental Sciences, 2010
The health hazard of mercury (Hg) compounds is internationally recognized, and the main pathways for methylmercury (MeHg) intake in humans are through consumption of food, especially fish. Given the large releases of Hg to the environment in China, combined with the fast development of hydropower, this issue deserves attention. Provided similar mobilization pathways of Hg in China as seen in reservoirs in North America and Europe one should expect increased Hg contamination in relation to future hydropower reservoir construction in this country. This study presents total Hg (THg) concentrations in wild fish from six Guizhou reservoirs, China. The THg concentrations in fish were generally low despite high background levels in the bedrock and depositions from local point sources. The over all mean ± SD concentration of THg was (0.066 ± 0.078) µg/g (n = 235). After adjusting for among-reservoir variation in THg, there were significant differences in THg among functional groups of the fish, assumed to reflect trophic levels. Predicted THgconcentration ratios, retrieved from a mixed linear model, between the functional groups were 9:4:4:1 for carnivorous, omnivorous, planktivorous and herbivorous fish. This result indicated that MeHg accumulation may prevail even under circumstances with short food chains as in this Chinese water system. No fish exceeded recommended maximum THg limit for human consumption set by World Health Organization and the Standardization Administration of China (0.5 µg/g fish wet weight (ww)). Only six fish (2.5%) exceeded the maximum THg limit set by US Environmental Protection Agency (0.3 µg/g fish ww).
Ecotoxicology, 2005
As part of an initiative to assemble and synthesize mercury (Hg) data from environmental matrices across northeastern North America, we analyzed a large dataset comprised of 15,305 records of fish tissue Hg data from 24 studies from New York State to Newfoundland. These data were summarized to provide mean Hg concentrations for 40 fish species and associated families. Detailed analyses were carried out using data for 13 species. Hg in fishes varied by geographic area, waterbody type, and waterbody. The four species with the highest mean Hg concentrations were muskellunge (Esox masquinongy), walleye (Sander vitreus), white perch (Morone americana), and northern pike (Esox luscius). Several species displayed elevated Hg concentrations in reservoirs, relative to lakes and rivers. Normalized deviations from mean tissue levels for yellow perch (Perca flavescens) and brook trout (Salvelinus fontinalis) were mapped, illustrating how Hg concentrations in these species varied across northeastern North America. Certain geographic regions showed generally below or above-average Hg concentrations in fish, while significant heterogeneity was evident across the landscape. The proportion of waterbodies exhibiting exceedances of USEPA's criterion for fish methylmercury ranged from 14% for standard-length brook trout fillets to 42% for standard-length yellow perch fillets. A preliminary correlation analysis showed that fish Hg concentrations were related to waterbody acidity and watershed size.
75-Canuel_MeHg-Fish-consumption-2006.pdf
Fish constitutes the main dietary protein source for many populations worldwide. However, the presence of methylmercury (MeHg) in fish flesh can affect the health of frequent fish consumers. Health risk assessment requires fitting the level of exposure of food-borne contaminants to a mathematical function relating exposure to effects on health . Most epidemiologic studies dealing with the MeHg issue use mercury (Hg) levels in hair as the only indicator of human exposure, without relating this signal to actual fish consumption patterns among populations. The expected constant and linear relation between MeHg oral dose and body burden is used by government officials to establish guidelines on safe levels of MeHg exposure. Our objective in the present study was to test the validity of this approach by relating measured exposure to MeHg through fish consumption and associated measured levels of Hg in human hair. Using information yielded by a) a complete data set that includes, for three distinct Canadian communities, fish consumption patterns, biomarkers of human exposure, and related levels of Hg in edible fish species; and b) reanalysis of other published research related to fish consumption and hair Hg concentrations, allowed us to demonstrate that Hg levels in hair do not always reflect the reported level of MeHg intake via fish consumption, and therefore, the expected constant and linear relation between MeHg oral dose and body burden seems to vary significantly among ethnic groups. This observation could lead to questioning of regulatory policies and advisory guidelines on fish consumption.