Seasonal variation in radiocesium levels of largemouth bass (Micropterus salmoides): Implications for humans and sensitive wildlife species

To examine seasonal variation in levels of radiocesium (Cs-137) within larg emouth bass (Micropterus salmoides; N = 589), fish were collected monthly o ver a one-year period from an abandoned reactor cooling reservoir. Month of collection, sex, age, and body mass (log transformed) were all significant factors influencing Cs-137 concentrations. Levels of Cs-137 reached a peak in late winter/early spring (February/March), and minimum values occurred in the fall (October). An asymmetric sawtooth model with a four-month perio d of increase and an eight-month period of decrease fit the data for monthl y 137Cs values significantly better than symmetric sinusoidal and sawtooth models. The mean concentration of Cs-137 for bass collected during all mont hs was 7.09 Bq/g wet mass.-All individuals examined, regardless of month, s ex, age, or body mass, had Cs-137 levels (2.95-12.60 Bq/g) that were much h igher than the maximum level (0.60 Bq/g wet mass) generally considered safe for human consumption. Radiocesium is relatively long-lived within this re servoir and will continue to remain an important issue in risk assessments for both humans and wildlife species.