Mercury accumulation in largemouth bass (Micropterus salmoides) in a Florida lake

Rates of mercury accumulation were examined in male and female largemouth bass (Micropterus salmoides) from Lake Tohopekaliga, Florida, to establish methods for fish consumption advisories for the protection of human health. In addition, concentrations were determined in five lower trophic level fish species. Total mercury concentrations in adult largemouth bass muscle tissue ranged from 0.16 to 1.10 micrograms/g (fresh weight) and increased as fish increased in size and age. Whole-body mercury concentrations of 1990 year-class largemouth bass increased from 0.05 microgram/g at 20 mm and to 0.32 microgram/g at 320 mm (age 2). Significant differences were found in the rates of accumulation between sexes for length and weight, but not for age. Therefore, standardized mercury concentrations were determined using bass age to make comparisons among sampling dates. Although there were significant differences in adjusted mean mercury concentrations among two sampling dates, mercury content of standard-age bass remained relatively constant over time. Largemouth bass exceed the Florida Health Advisory level for limited consumption of fish (0.50 microgram Hg/g) based on a mean concentration of 0.59 microgram/g for 64 bass. Advisories based on fish morphological characteristics (i.e., length, weight) or age are not possible for Lake Tohopekaliga due to differences in mercury accumulation in male and female bass. Lower trophic level species of sport fish did not exceed the limited consumption level.