On Tuesday, October 10, 2006 Richard Peterson will be presenting a "Retrospective Risk Assessment of Sac Fry Mortality in Lake Ontario Lake Trout." The seminar will begin at 12:00 noon in the Redfield Auditorium.

Retrospective Risk Assessment of Sac Fry Mortality in Lake Ontario Lake Trout

Richard E. Peterson  PhD

School of Pharmacy and Molecular and Environmental Toxicology Center

University of Wisconsin

Tuesday, October 10, 2006

12:00 Noon

Redfield Auditorium

Woods Hole Oceanographic Institution

45 Water Street

Woods Hole

Over fishing and sea lamprey predation caused the historic decline of the lake trout population in Lake ontario, but not the more recent lack of recruitment.  The discovery that increases in lake trout sac fry mortality from 0 to 100% occurred with exposure of embryos from 30 to 100 pg TCDD/g egg, led to a chemical etiology investigation.  To estimate lake trout egg exposures to TCDD-like chemicals from 1920 to 1987, radionuclide-dated 1 cm segments of sediment cores from depositional basins in Lake Ontario were analyzed.  Biota-sediment accumulation factors (BSAFs) were measured for lake trout eggs and used with sediment core data to predict historical embryo exposures.  The additive TCDD toxicity equivalence factor (TEF) approach was used to calculate TCDD equivalent (TEQ) concentrations in lake trout eggs. It was predicted that 100% mortality of lake trout sac fry occurred from the 1940s into the 1970s due to egg contamination by TCDD-like chemicals.

Note: Dick also will be giving an informal presentation of recent findings on mechanisms of dioxin developmental toxicity from studies using the zebrafish model. Time TBD.

Sponsored by : Superfund Basic Research Program at Boston University and the Biology Department, Woods Hole Oceanographic Institution

Contact: Mark Hahn ( This e-mail address is being protected from spambots, you need JavaScript enabled to view it )