Some Effects of Kraft Mill Effluent on Young Pacific Salmon

Abstract

Sockeye salmon underyearlings (Oncorhynchus nerka) were exposed to various concentrations of full-bleach kraft mill effluent under experimental conditions simulating those anticipated in the estuary of the Somass River at the head of Alberni Inlet, B.C. An anticipated expanded production of a kraft pulp mill discharging effluent into this area was regarded as a potential source of pollution which could influence survival of young salmon migrating into and through the estuary. A 4.8% concentration of effluent by volume in sea-water of 20‰ salinity at 17.8 °C. was a limiting concentration for toxicity, below which survival was complete and independent of length of exposure. However, when oxygen requirements for respiration were considered and were compared with net oxygen availability after effluent oxidation in the area, the interaction of toxicity of the effluent and lowered oxygen availability suggests that the limiting concentration of effluent in this particular case be lowered from 4.8 to 2.5% effluent.