BIOASSAY-DERIVED 2,3,7,8-TETRACHLORODIBENZO-PARA-DIOXIN EQUIVALENTS IN PCB-CONTAINING EXTRACTS FROM THE FLESH AND EGGS OF LAKE-MICHIGAN CHINOOK SALMON (ONCORHYNCHUS-TSHAWYTSCHA) AND POSSIBLE IMPLICATIONS FOR REPRODUCTION

Concentrations of 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TCDD-EQ), derived via the H4IIE rat hepatoma cell bioassay, were measured in polychlorinated biphenyl (PCB) containing extracts of flesh (dorsal muscle) and egg samples from 10 spawning chinook salmon (Oncorhynchus tshawytscha) from Lake Michigan. There was a marked maternal transfer of both TCDD-EQ and PCBs, and potency of the PCB mixture (expressed as picograms of TCDD-EQ per microgram of PCB) in eggs was 2.5 times greater than potency of the PCB mixture in dorsal muscle of the fish. There was a statistically significant, inverse relationship between the total concentration of PCBs in eggs and hatching success of the fish, with an effect concentration that corresponded to approximately 100 pg TCDD-EQ/g egg. Our results, based on a relatively small sample size, suggest that PCBs, in particular those with TCDD-type activity, may have influenced reproductive success of the fish.