How Will Decreased Alewife Growth Rates and Salmonid Stocking Affect Sport Fish PCB Concentrations in Lake Ontario?

摘要

Atmospheric deposition and resuspension from pelagic sediments are the two principal PCB sources to Great Lakes pelagic food webs today. The expansive nature of these sources makes their management and control impractical. Fisheries management, such as the numbers and species of salmonids stocked, represents a potential mechanism by which PCB concentrations in sport fish may be further reduced. I used a simulation model to examine the effect of alewife growth rates, alewife PCB concentrations, and stocking scenarios on sport fish PCB concentrations over the next decade. Eliminat- ing lake trout is predicted to have little effect gn growth rates and PCB concentrations of the remaining salmonids. However, eliminating chinook salmon will maximize growth rates of the remaining species and is predicted to lead to a 15% decline in lake trout PCB concentrations. If alewife growth rates decline, sport fish growth rates will also decline, and their PCB concentrations will increase. Reduced salmonid stocking carries the risk that alewife survival may increase, leading to a greater number of older and more contaminated alewife. If the average alewife consumed went from an age class 3+ to a 6+ fish, sport fish PCB concentrations are predicted to increase by 40% (lake trout) to 60% (chinook salmon and steelhead). Thus, prey PCB concentrations are likely to play a more important role than salmonid growth rates in determining salmonid PCB concentrations.