Effects of hypoxia on scope-for-activity and power capacity of lake trout (Salvelinus namaycush)

Abstract

This study develops a quantitative model of the combined effects of temperature and ambient dissolved oxygen on metabolic scope-for-activity and power capacity of juvenile lake trout (Salvelinus namaycush). The model provides a framework for evaluating the effects of hypoxia on the capacity of lake trout to perform critical daily life support activities. Maximum power output for sustained swimming of yearling lake trout occurred at 12–20 °C and a dissolved oxygen concentration of >7 mg·L–1. At 4–8 °C, temperatures typical of the hypolimnetic summer habitat of juvenile lake trout, maximum power capacity was reduced by 33%, 67%, and 100% at ambient dissolved oxygen concentrations of 7, 5, and 3 mg·L–1, respectively. Analysis of power outputs, growth impairment, and recruitment success indicated that attainment of 3/4 power capacity would accommodate most daily life support activities of juvenile lake trout. At 4–14 °C, the threshold dissolved oxygen concentration for attainment of 3/4 scope-for-activity varied from 7.5 to 6.6 mg·L–1, respectively, with a mean and standard deviation of 7.04 ± 0.33 mg·L–1. A dissolved oxygen criterion of 7 mg·L–1is recommended for protection of the hypolimnetic habitat of juvenile lake trout.