Influence of ambient oxygenation and temperature on metabolic scope and scope for heart rate in the common sole Solea solea

The objective of this study was to quantify the constraints exerted by temperature and oxygenation on both metabolic scope and scope for heart rate of the common sole Solea solea. We exposed sole to a large range of temperature and oxygenation conditions and a modelling procedure was implemented to describe metabolic and cardiac responses. Standard metabolic rate (SMR) rose exponentially from 4 to 24degreesC, whereas active metabolic rate (AMR) increased from 55.4 to 159.2 mgO(2) kg(-1) h(-1) between 4 and 19.7degreesC, and then dropped to 129.9 mgO(2) kg(-1) h(-1) at 24degreesC. In parallel, optimal temperature for maximising metabolic scope, defined as the difference between AMR and SMR, was estimated to 18.8degreesC. Active heart rates increased linearly with temperature and attained 15, 79 and 97 beats min(-1) at 4, 20 and 24degreesC, respectively. Hyperoxia had no influence on maximal heart rate nor on maximal metabolic rate. In hypoxic conditions, on the other hand, a significant decrease of the maximal metabolic rate was recorded when oxygen dropped below 75% air saturation. A significant decrease in maximal heart rate was also detected below 50% at 16 and 20degreesC, and below 25% air saturation at 8degreesC. The potential ecological consequences of the variation in sole metabolic and cardiac performances are discussed.