AbstractThe sensitivity of early life stages of brook trout (Salvelinus fontinalis) to 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD) toxicity was investigated. Newly fertilized eggs were exposed for 48 h to water containing either acetone or a range of concentrations of 3HTCDD dissolved in acetone. Eggs were then transferred to TCDD‐free water and observed through development. TCDD concentrations of 101 to 470 pg/g in the eggs caused dose‐related increases in sac‐fry mortality associated with yolk‐sac edema, hemorrhages, and arrested development. These signs of TCDD‐induced toxicity resemble blue‐sac disease. The NOELs and LOELs for sac‐fry mortality were 135 and 185 pg TCDD/g egg, respectively, whereas the LD50 and LD100 (95 fiducial limits) were 200 (179‐215) and 324 (283‐488) pg/g egg, respectively. The time course and signs of TCDD toxicity to brook trout during early development are essentially identical to those observed in both rainbow trout and lake trout following TCDD exposure of their eggs via water or injection, and in lake trout exposed to maternally derived TCDD. Brook trout sac fry are intermediate in sensitivity to TCDD‐induced lethality compared to lak
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