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 concent ration in zooplankton, mysids, amphipods, slimy sculpin (Cottus cognat us), rainbow smelt (Osmerus mordax), alewife (Alosa pseudoharengus), a nd lake trout (Salvelinus namaycush) in Lake Ontario were determined f or samples collected from 1989 to 1992. Amphipods, and to a lesser ext ent sculpins, had higher DDE and PCB concentrations than predicted fro m the contaminant concentration - body size relationship for the pelag ic 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 rel ationship had a slope of 0.23 (95% confidence limits = +/-0.014). Comb ined with revised estimates of the efficiency of contaminant retention from one body size to another (epsilon' = 0.05-0.10), the revised est imate of particle-size-conversion efficiency (epsilon) for Lake Ontari o falls between 0.27 and 0.35. Recent estimates of invertebrate (zoopl ankton, mysid, and amphipod) annual production average 18 g/m2 (dry we ight) with upper and lower limit estimates of 14-27 g/m2. Using epsilo n to extrapolate from invertebrate to fish production results in estim ates of mean potential fish production in Lake Ontario of 1-7 kg/ha (w et weight), as compared with previously published estimates of 6 and 1 4 kg/ha.