RELATIONSHIPS AMONG CONCENTRATIONS OF INDIVIDUAL POLYCHLORINATED BIPHENYL (PCB) CONGENERS, 2,3,7,8-TETRACHLORODIBENZO-P-DIOXIN EQUIVALENTS (TCDD-EQ), AND REARING MORTALITY OF CHINOOK SALMON (ONCORHYNCHUS-TSHAWYTSCHA) EGGS FROM LAKE-MICHIGAN

A study was conducted to investigate possible correlations between concentrations of individual polychlorinated biphenyl congeners (PCBs) or 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TCDD-EQ) and mortality in early life stages of chinook salmon. Eggs were collected from adult Lake Michigan chinook salmon in October, 1986, and were analyzed for concentrations of individual PCB congeners and total PCBs. Concentrations of mono- and non-ortho-substituted congeners were determined after fractionation of PCB-containing extracts with a carbon column. Three types of TCDD-EQ were calculated using an additive potency model by multiplying concentrations of individual PCB congeners by each of three different sets of toxic equivalency factors (TEFs) and summing the products. The mean total concentration of PCBs in the eggs was 7.02-mu-g/g, wet weight, and measured concentrations of the non-ortho-substituted PCB congeners ranged from 0.2 to 12 ng/g, wet weight. Mean concentrations of TCDD-EQ depended on the set of TEFS which were used in the calculations and ranged from 29 to 514 pg/g. Concentrations of TCDD-EQ were positively correlated with total concentrations of PCBs (r2 = 0.60), although the magnitude of correlations between concentrations of individual non-ortho-substituted congeners and total PCBs were less than those for TCDD-EQ and total PCB. Mortality of eggs and fry differed significantly among clutches of eggs from different females but was not correlated with concentrations of TCDD-EQ, individual PCB congeners, or total PCBs in the eggs.