Physiological effects of thermomechanical newsprint mill effluent on Atlantic salmon (Salmo salar L.)

Anadramous Atlantic salmon (Salmo salar L.) returning to Exploits River, Newfoundland, Canada, to spawn encounter low concentrations of thermomechanical pulp (TMP) effluent as they migrate upstream past an integrated newsprint mill. Various physiological responses of adult Atlantic salmon from the Exploits River were studied under laboratory conditions. The effects of a 6-h exposure to 0%, 6%, 12%, or 25% (v/v) TMP effluent or an increasing concentration gradient of effluent (0-25%) on cardiac output (Q ), critical swimming performance (U(crit)), hematocrit, and blood glucose, cortisol, lactate, and osmolality were examined. Relative to other treatment groups, Q during routine and low-level activity was 7-10% higher in fish exposed to at least 12% effluent. The 25% exposure group had a distinctly lower U(crit) and scope for increase in Q than the other treatment groups. These findings suggest that effluent exposure elevates physiological maintenance and repair costs, resulting in a reallocation of energetic resources.