Sexual and seasonal variations of mercury in smallmouth bass

We assessed sexual and seasonal variations of total mercury in the muscle tissue of smallmouth bass (Micropterus dolomieu) in the South Fork of the Shenandoah River, Virginia. The average concentration of total mercury in the muscle tissue of bass sampled was 0.79 mu g/g wet weight and ranged from 0.30 to 1.38 mu g/g. There were significant positive relationships between the mercury level in muscle tissue and the length, weight, and age of bass sampled. Mean concentrations of total mercury differed significantly between sexes following adjustment for length and weight and were 20% higher in females than males. Differences among seasons were nearly significant after adjustment for length and were 14 and 21% higher during spring than summer and fall following adjustment for length and weight. Results of this study indicate that state and federal agencies should account for sex and season during mercury monitoring and assessment programs to assure more accurate and precise data that can be compared among water bodies and monitored over time.