Effects of bleached kraft mill effluent on early life stages of brown trout (Salmo trutta L.).

Brown trout (Salmo trutta L.) eggs fertilized in clean water were incubated in bleached kraft mill effluent (BKME) concentrations of 0, 0.5, 1, and 2% (v/v) in a continuous-flow system and exposure was continued with the sac fry for most of the yolk sac stage. In addition, sac fry first incubated in clean water were exposed after hatching to the same concentrations for 44 days. Percentage hatching was lower than in the control only in 2% BKME. In all the BKME concentrations, the newly hatched sac fry were shorter than the controls, and their heart rate was slower. All the sac fry in 2% BKME died within 3 weeks after the end of hatching. At the late yolk sac stage the sac fry in the other concentrations of BKME were shorter and less well developed than the controls. Their wet and dry weights were higher and their water content was lower because of retarded yolk absorption. Exposure commencing after hatching also caused retarded growth and development. In the sac fry exposed to BKME only after hatching, mortality increased with the concentration and all the sac fry in 2% BKME died within 4 weeks.