Evaluation of Biopsy Plug Samples Versus Homogenized Fillets for Monitoring Mercury and Selenium in Fish Tissue

Collaborative Efforts to Improve Environmental Monitoring
Oral Presentation

Prepared by H. McCarty1, B. Snyder2, T. Cohen3, J. Healey4, M. Fernandez5, K. Miller1
1 - General Dynamics Information Technology, 3170 Fairview Park Drive, 4th floor, Falls Church, Virginia, 22003, United States
2 - Tetra Tech, 10711 Red Run Blvd.,, Suite 105, Owings Mills, Maryland, 21117, United States
3 - Tetra Tech, 10711 Red Run Blvd, Suite 105, Owings Mills, 21117, United States
4 - USEPA, 1200 Pennsylvania Ave, NW, M/C 4305-T, Washington, DC, 20460, United States
5 - Tetra Tech, 10711 Red Run Blvd., Suite 105, Owings Mills, Maryland, 21117, United States

Contact Information: [email protected]; 703-254-0093


Monitoring contaminant bioaccumulation in fish is important to ensure human health protection and to communicate risks associated with fish consumption. Biopsy punch (or fish plug) sampling has recently been applied in some fish monitoring programs as a more cost-effective alternative to obtain contaminant data than homogenizing and analyzing entire fillets. However, the degree to which fish plug results are representative of homogenized fillet results is largely unknown. EPA’s Office of Water conducted a Fish Plug Evaluation Study to address the fundamental question of whether fish plug analysis can serve as a reliable alternative for analyzing whole fillet tissue to monitor mercury and selenium concentrations in fish. The study also addressed the applicability of using fish plugs for assessment monitoring associated with EPA’s 300 ng/g (wet weight) fish tissue-based methylmercury water quality criterion, as well as EPA’s recommended national chronic aquatic life criterion for selenium in freshwater. Six target species of fish consumed by humans were collected from three Great Lakes and three eastern U.S. rivers for mercury analysis. Ten specimens of each of the six species were used to prepare fish tissue samples, including five replicate field-extracted plug samples and five replicate samples of homogenized fillet tissue, yielding 600 samples for mercury analysis. For selenium analysis, five specimens of three species each were collected. Four replicates each of field-extracted plugs and homogenized whole samples, yielding 240 samples for selenium analysis. An ANOVA was used to test the comparability of mercury and selenium results from field-extracted plugs and homogenized fillet tissue. There were no statistically significant differences between fillet plug and homogenized fillet results for either mercury or selenium at the community level. These data support the conclusion that the choice between these two sampling techniques ultimately depends on study objectives, target chemicals, and tissue volumes needed for analysis.