Maternal transfer of organochlorines to eggs of walleye (Stizostedion vitreum) in Lake Manitoba and western Lake Superior

Gravid walleye were sampled from Lake Manitoba and western Lake Superior (S t. Louis River) to measure the concentrations of organochlorine contaminant s (OCs) in eggs and muscle and to assess the influence of maternal age and size on the transfer OCs from mother to egg. Concentrations of most OCs in Lake Superior walleye eggs were I to 3 orders of magnitude greater than in Lake Manitoba eggs. Toxaphene (mean concentration (wet weight) +/- I SE, 15 80 +/- 462 ng/g) and polychlorinated biphenyls (PCBs) (240 +/- 24 ng/g) wer e the predominant OCs in Lake Superior walleye Eggs, whereas DDT and metabo lites (eggs 16 +/- 1.5 ng/g, muscle 2.1 +/- 0.36 ng/g) and PCBs (eggs 9.2 /- 0.83 ng/g, muscle 2.0 +/- 2.4 ng/g) were the most common OCs. in Lake Ma nitoba walleye eggs and female muscle. Egg size (dry mass) and the concentr ation of most OCs in Lake Manitoba walleye eggs were positively correlated with female length and age. This relationship was strongest for more hydrop hobic OCs (e.g., PCBs) but was not significant for less hydrophobic OCs (e. g., hexachlorocyclohexanes (HCHs)). Neither egg size nor egg OC concentrati on of Lake Superior walleye were significantly correlated with female lengt h or age. There was no relationship between OC concentrations in muscle tis sue and female length or age of Lake Manitoba walleye. OC concentrations in Lake Manitoba walleye eggs were not correlated with concentrations in the muscle tissue of the mothers, suggesting that OCs in walleye eggs are deriv ed from various tissues. A positive relationship between the egg:muscle rat io of PCB concentrations and the egg:muscle ratio of lipid in freshwater fi sh suggests that the maternal transfer of PCBs in freshwater fish is relate d to the relative amounts of lipid in the eggs and mother. The transfer of hydrophobic OCs from mother to eggs in freshwater fish appears to vary with in and among fish species and with the hydrophobicity of the OC.