Mercury in fish scales as an assessment method for predicting muscle tissue mercury concentrations in largemouth bass

The relationship between total mercury (Hg) concentration in fish scales and in tissues of largemouth bass (Micropterus salmoides) from 20 freshwater sites was developed and evaluated to determine whether scale analysis would allow a nonlethal and convenient method for predicting Hg concentrations in tissues. The relationship between total Hg concentration in untreated scale samples and muscle tissue is highly variable. Several different scale treatments were tried in an effort to increase the coefficient of determination and thereby enhance the effectiveness of this predictive technique. Washing scales with acetone, deionized (DI) water, detergent solution, and soap were used in conjunction with ultrasonication. The use of a mild soap solution with heating and ultrasonication increased the r(2) the most (from 0.69 [untreated scales] to 0.89). However, despite treatment, wide predictions of tissue Hg concentration remained. These results suggest that application of this technique as an independent method for issuance of fish advisories is inappropriate. Nevertheless, our results showed that scale analysis has potential for assessing general trends in concentration relative to a tissue criterion and for assessing Hg contamination in fish tissue as a first-level screen.