USE OF A SIMULATION-MODEL TO RECONSTRUCT PCB CONCENTRATIONS IN PREY OF LAKE-ONTARIO LAKE TROUT

Although the alewife (Alosa pseudoharengus) has been the principal pre y fish of adult lake trout (Salvelinus namaycush) in Lake Ontario, a l akewide survey of PCB concentration in Lake Ontario alewife was not at tempted until 1986. We applied an individual-based model to the 1986 p opulation of Lake Ontario lake trout to (a) estimate the PCB concentra tion in alewife prior to 1986 and (b) determine the amount of variabil ity in PCB concentrations of fake trout prey. Modeling results indicat ed that the PCB concentration in adult alewife during 1979-1985 was on the average almost four times greater than the adult alewife PCB conc entration observed in 1986. This result suggested that PCB concentrati on in lake trout prey may fluctuate widely from year to year, perhaps in response to changes in age structure and growth of prey fishes, Sec ondly, modeling results suggested that spatial variability in the PCB concentrations of lake trout prey was probably greater in Lake Ontario than in Lake Michigan.