Warming effects on trout energetic efficiency

Data and R code from metabolic and feeding rate experiments conducted across streams of different temperature in the Hengill geothermal valley in Iceland. Fish were collected from one cold and two warm streams in the system and acutely exposed to different experimental temperatures (using the natural temperature gradient of the streams) to measure the mass and temperature dependence of metabolic and feeding rates. Metabolism experiments lasted 2.5 hours and were conducted in situ in 7.2 litre plastic chambers containing a dissolved oxygen probe. Feeding rate experiments lasted approximately 24 hours and were conducted in situ in 250 mm diameter x 300 mm height cylindrical plastic arenas with 20 individuals of the snail Radix balthica or blackfly larvae from the Simuliidae family and a rock for shelter. The energetic efficiency of brown trout was calculated as the dimensionless ratio of feeding rate to metabolic rate. At the end of the experiments, a subset of fin clips were taken for population genetics, with 17 microsatellites genotyped.