Differential survival of juvenile sockeye and coho salmon exposed to low dissolved oxygen during winter.

摘要

The survival of juvenile sockeye salmon (Oncorhynchus nerka) and coho salmon (O. kisutch) exposed to low oxygen concentration in Black Lake (Alaska) was studied during February 1992 and 1995. Groups of 10-20 coho salmon from Black Lake or sockeye salmon from nearby Chignik Lake (264 sockeye and 145 coho total) were placed in cages which were lowered to various depths. Fish were exposed to oxygen concentrations of 6.0-100% (0.9-14.2 mg/litre) and temperatures of 0.4-2.7oC. Over a 24-h period sockeyesalmon survival was 100% when oxygen levels exceeded 6% or 9.0 mg/litre, declined to 90-97% at concentrations of 65-34% (4.5-9.0 mg/litre) and fell markedly at concentrations below 30% (4 mg/litre). At 24% saturation (3.0-3.3 mg/litre) 45% of sockeye survived but none survived exposure to concentrations <17% saturation (2.3 mg/litre). All coho salmon survived exposure to oxygen concentrations as low as 21% of saturation (3.1 mg/litre). 50 coho exposed to 23-24% saturation (3.2-3.3 mg/litre) for 4-5 days all survived.