ESTIMATE OF NET TROPHIC TRANSFER EFFICIENCY OF PCB TO LAKE-MICHIGAN LAKE TROUT FROM THEIR PREY

Most of the polychlorinated biphenyl (PCB) body burden accumulated by lake trout (Salvelinus namaycush) from the Laurentian Great lakes is f rom their food. We used diet information, PCB determinations in both l ake trout and their prey, and bioenergetics modeling to estimate the e fficiency with which Lake Michigan lake trout retain PCBs from their f ood. Our estimates were the most reliable estimates to date because (a ) the lake trout and prey fish sampled during our study were all from the same vicinity of the lake, (b) detailed measurements were made on the PCB concentrations,of both lake trout and prey fish over wide rang es in fish size, and (c) lake trout diet was analyzed in detail over a wide range of lake trout size. Our estimates of net trophic transfer efficiency of PCBs to lake trout from their prey ranged from 0.73 to 0 .89 for lake trout between the ages of 5 and 10 years old. There was n o evidence of an upward or downward trend in our estimates of net trop hic transfer efficiency for lake trout between the ages of 5 and 10 ye ars old, and therefore this efficiency appeared to be constant over th e duration of the lake trout's adult life in the lake. On the basis of our estimates, lake trout retained 80% of the PCBs that are contained within their food.