Evaluation of nonlethal methods for the analysis of mercury in fish tissue

Thousands of fish are sacrificed each year to determine potential human exposure to mercury (Hg) front fish consumption. In this paper, we use lake whitefish Coregonus clupeaformis and northern pike Esox lucius to demonstrate that accurate and reliable measures of fish muscle Hg concentrations can be determined from small samples (< 100 mg) harvested with biopsy tools. Reliability of results primarily depends upon analytical methodology and tissue sample weight. Mercury concentrations estimated by use of cold-vapor atomic absorption spectrophotometry (CVAAS) on small composite tissue samples harvested with a Tru-Cut (TC) biopsy needle (mean sample wet weight = 47 mg) were less precise than estimates from tissue samples harvested with a dermal punch (DP; mean sample wet weight = 126 mg). Precision differences presumably occurred because TC samples weighed less than the prescribed minimum weight (>100 mg) for CVAAS. There was no difference in precision of Hg concentrations among tissue extraction methods when biopsy samples were analyzed via cold-vapor atomic fluorescence spectrophotometry (CVAFS). Mean tissue Hg concentrations obtained with the biopsy techniques and CVAAS or CVAFS were similar to benchmark concentrations in fillet samples (within 6%), even for TC-CVAAS. A field study of the effects of the DP biopsy method on survival of northern pike showed that tissue harvesting did not reduce survival. Our results clearly demonstrate that analysis of Hg content in muscle harvested with biopsy tools provides Hg measures comparable in accuracy to traditional, whole-fish methods but without causing mortality.