PARTICLE-SIZE-CONVERSION EFFICIENCY, INVERTEBRATE PRODUCTION, AND POTENTIAL FISH PRODUCTION IN LAKE-ONTARIO

The relationships between body size and p,p'-DDE and total PCB concentration in zooplankton, mysids, amphipods, slimy sculpin (Cottus cognatus), rainbow smelt (Osmerus mordax), alewife (Alosa pseudoharengus), and lake trout (Salvelinus namaycush) in Lake Ontario were determined for samples collected from 1989 to 1992. Amphipods, and to a lesser extent sculpins, had higher DDE and PCB concentrations than predicted from the contaminant concentration - body size relationship for the pelagic species. PCB, but not DDE, concentrations in zooplankton were also abnormally high. For the pelagic species, excluding PCB concentrations in zooplankton, the log contaminant concentration - log body size relationship had a slope of 0.23 (95% confidence limits = +/-0.014). Combined with revised estimates of the efficiency of contaminant retention from one body size to another (epsilon' = 0.05-0.10), the revised estimate of particle-size-conversion efficiency (epsilon) for Lake Ontario falls between 0.27 and 0.35. Recent estimates of invertebrate (zooplankton, mysid, and amphipod) annual production average 18 g/m2 (dry weight) with upper and lower limit estimates of 14-27 g/m2. Using epsilon to extrapolate from invertebrate to fish production results in estimates of mean potential fish production in Lake Ontario of 1-7 kg/ha (wet weight), as compared with previously published estimates of 6 and 14 kg/ha.