Toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) during lake trout early life stage development

The presence of halogenated aromatic hydrocarbons has been proposed to explain early life stage mortality seen in lake trout (Salvelinus namaycush) from the Great Lakes. Three years of experiments show that lake trout sac fry are extremely sensitive to TCDD. Newly fertilized lake trout eggs exposed to vehicle or graded water concentrations of 3H-TCDD for 48 hr accumulated 0, 40, 55, 60, 70, 110, 150, 170, 280, 370 or 530 ppt (pg 3H-TCDD/g egg). The 3H-TCDD persisted in the egg and sac fry stages (t1/2 = 349 days), but was rapidly eliminated in the fry stage (t1/2=40 days). Egg stage mortality was unaffected by TCDD (11%, mean); however, at the onset of hatching there was a dose-related increase in larvae dying half-hatched. The greatest dose-related mortality occurred in the sac fry stage and was associated with subcutaneous edema of the yolk sac membrane and hemorrhages, morphologically resembling blue-sac disease. Cumulative mortality at swim up was 19% (vehicle), 20-28% (40-60), 45% (70), 74% (110), and 100% (≥150 ppt 3H-TCDD). The LD50 in sac fry based on the 3H-TCDD egg burden was 75 ppt (71-77 ppt, 95% C.I.)