Effects of DDT and PCB's on Survival of Lake Trout Eggs and Fry in a Hatchery and in Lake Michigan, 1973–1976

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Abstract
To assess the role of DDT and PCBˈs in reproductive failure of lake trout (Salvelinus namaycush) planted in Lake Michigan, I compared mortality of eggs (1.41–5.24 μg/g DDT, 3.16–9.90 μg/g PCBˈs) and fry from planted Lake Michigan lake trout with that of eggs (0.05–0.20 μg/g DDT, 0.20–0.28 μg/g PCBˈs) and fry from hatchery lake trout. In normal hatchery incubation from fertilization to 6 weeks after swim‐up, mortality of Lake Michigan trout (mean ± 95% confidence limits) was 80 ± 16% as compared to 46 ± 14% for hatchery lake trout in 1973–1974 and 50 ± 9% versus 47 ± 9%, respectively, in 1974–1975. The significantly higher mortality of Lake Michigan than of hatchery lake trout in 1973–1974 was thought due to causes other than DDT or PCBˈs. Mortality of Lake Michigan lake trout during different stages of development usually was not linearly correlated with DDT and PCB content. During development in enclosures in Lake Michigan from fertilization or the eyed stage, mortality of Lake Michigan lake trout usually was not significantly greater than that of hatchery fish at eye‐up, at swim‐up, and at 3 weeks after swim‐up. In hatchery tests, Lake Michigan fry mortality (65 ± 6%) was significantly less than that of hatchery fry (89 ± 6%) after 11 weeks of starvation and was the same (53 ± 11% versus 61 ± 11%) when fry were stressed by half rations for 10 weeks in the presence of similar‐sized brown trout (Salmo trutta). The bulk of the evidence indicated that DDT and PCBˈs did not have an effect on early survival of Lake Michigan lake trout.

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