Reproductive toxicity and disposition of 2,3,7,8-tetrachlorodibenzo-p- dioxin in adult brook trout (salvelinus fontinalis) following a dietary exposure

Adult brook trout (Salvelinus fontinalis) were exposed to 2,3,7,8- tetrachlorodibenzo-p-dioxin (TCDD) with a contaminated trout pellet diet to determine the effects of TCDD on reproduction, to document tissue-specific TCDD distribution, and to establish the maternally derived dose of TCDD to the F₁ generation. Five treatment groups and a control were exposed to achieve targeted whole body TCDD concentrations of 0, 75, 150, 300, 600, and 1,200 pg TCDD per gram fish. Net dietary assimilation of TCDD was estimated to be 89% of the applied dose, and the distribution of TCDD generally followed the distribution of lipids in liver, gonad, fat, blood, and muscle. Depuration could not be measured over 81 d, but a hypothetical depuration rate was estimated to be 0.002 d^-1 assuming 100% dietary assimilation. The concentration of TCDD in ovaries and spawned eggs was estimated to be 61 and 39% of the whole body TCDD concentrations, respectively. Survival, growth, gonadal development, and egg production were not affected in any treatment. The onset of spawning was delayed by 13 d in the highest treatment group, suggesting that TCDD might have affected ovulation. Otherwise, the adult life stage was not as sensitive to TCDD as the early life stage.