Reproductive fitness of lake trout (Salvelinus namaycush) exposed to environmentally relevant concentrations of the potent estrogen ethynylestradiol (EE2) in a whole lake exposure experiment

The synthetic estrogen, ethynylestradiol (EE2), has been identified in many aquatic environments. EE2 induces biochemical and physiological effects in exposed fish, but linkages to widespread reproductive dysfunction in populations have not been established. Mortality in early life stages has only been documented at relatively high concentrations, above those found in the environment. To examine the potential effects of environmentally relevant concentrations of EE2, reproductive endpoints were examined in lake trout (Salvelinus namaycush) captured from a lake experimentally treated with ∼5 ng/L EE2. Monitoring began two years prior to EE2 additions in the lake and for 3 years of additions. A nearby lake in which no EE2 was added was used as a reference. Eggs from fish in each lake were fertilised with milt from the same fish stocks. Fertilization and hatch, mortality, deformities, and size of the fry at swim up were not negatively affected by EE2 exposure. While our earlier studies have reported impaired reproductive success in small-bodied fish exposed to EE2 in the same system, lake trout appear to be less affected at the biochemical level and no impacts were determined in other reproductive and population level impacts.