Seasonal Changes and Tissue Distribution of Mercury in Largemouth Bass (Micropterus salmoides) from Dorena Reservoir, Oregon

Mercury contamination in fish has lead to the issuance of fish consumption advisories in many water bodies of the United States. There is evidence that mercury concentrations may fluctuate seasonally, which could affect consumption advisories. Largemouth bass (Micropterus salmoides) were collected from Dorena Reservoir, Oregon, in spring and summer of 1995 and spring, summer, and fall of 1996. Samples of muscle, liver, and gonad were analyzed for total mercury. There were seasonal differences for mercury in liver and gonads, but not muscle tissue. Liver mercury concentrations were higher in summer and lower in spring whereas ovarian mercury concentrations were higher in fall and lower in spring. This study shows that liver tissue was more sensitive than muscle tissue to seasonal variability of mercury, but these seasonal fluctuations may not influence consumption advisories. Received: 20 April 1999/Accepted: 27 July 1999