Influence of water temperature and oxygenation on the aerobic metabolic scope of Atlantic cod (Gadus morhua)

Environmental influences (temperature and oxygenation) on cod metabolism an d their impact on the ecology of this species were investigated. Limiting o xygen concentration curves (O-2 level ranging between 15 and 100% air satur ation) were established at 2, 5 and 10 degreesC. The standard metabolic rat e (SMR), the maximum metabolic rate and the metabolic score were then model led as functions of temperature and/or oxygen saturation. The mean SMR at 2 , 5 and 10 degreesC were 19.8 +/- 4.9, 30.8 +/- 6.1 and 54.3 +/- 4.1 mg O-2 h(-1) kg(-1). respectively. Between 2 and 5 degreesC, the active metabolic rate of cod almost doubled from 65 to 120 mg O-2 h(-1) kg(-1), to reach 17 7 mg O-2 h(-1) kg(-1) at 10 degreesC. In terms of metabolic scope (MS), the temperature rise from 7 to 5 degreesC resulted in a two-fold increase from 45 to 89 mg O-2 h(-1) kg(-1), with MS reaching 123 mg O-2 h(-1) kg-l at 10 degreesC. Our proposed model describing the impact of temperature and oxyg en level provides new insight into the energetic interactions which govern the relationship between Atlantic cod and its environment. We re-examined p ublished experimental and field studies from the angle of the regulation of metabolic power. We suggest that, when faced with heterogeneous or unstabl e hydrological conditions, cod tend to behaviourally maximise their metabol ic scope. Through this: adaptive response, fish reduce energy budgeting con flicts and presumably increase the probability of routinely operating away from lethal boundaries. (C) 2000 Elsevier Science B.V. All rights reserved.