Effects of wood-related sterols on the reproduction, egg survival, and offspring of brown trout (Salmo trutta lacustris L.)

Maturing lake trout (Salmo trutta lacustris) of both sexes were exposed to 10 and 20 mu g/liter phytosterols, mainly beta-sitosterol, for 4.5 months p rior to spawning. Eggs from preexposed females were artificially fertilized with milt from preexposed males in clean water, whereupon the eggs were in cubated in clean,vater until hatching. Yolk sac fry were followed until swi m-up, and mortality as well as deformities was recorded. The physiological status of the parent fish was documented, as was the occurrence of phytoste rols in bile liquid and gonads. In addition, eggs from preexposed females w ere fertilized with milt from unexposed males to evaluate the existence of possible sex-linked differences. The results indicate a markedly increased dose-dependent egg mortality, smaller egg size, and lower mean weight of th e the yolk sac stage larvae, There was a higher prevalence of deformed or o therwise diseased larvae, especially at the higher dose, but also in the gr oups where unexposed males were used for fertilization, indicating a female -linked effect mechanism. A causal link between effects on eggs and brood w as obtained through a dose-dependent increase in physiological in the roe, Several physiological parameters (higher plasma estradiol, higher 7-ethoxyr esorufin O-deethylase activity) implied slower maturation of the exposed fe male fish, whereas indications of accelerated maturation were obtained for the male fish from the same groups. The results indicate that naturally occ urring wood-derived compounds in pulp mill effluents may be responsible for reproductive impacts previously observed in fish both in the laboratory an d in the receiving waters of pulp mill effluents, The results also suggest that more attention should be paid to process streams emanating from the un bleached part of the mill. (C) 1999 Academic Press.