Competitive exclusion along climate gradients: energy efficiency influences the distribution of two salmonid fishes

• Published in: Global change biology Vol. 17; no. 4; pp. 1703 - 1711
• Main Authors: FINSTAD, ANDERS G, FORSETH, TORBJØRN, JONSSON, BROR, BELLIER, EDWIGE, HESTHAGEN, TRYGVE, JENSEN, ARNE J, HESSEN, DAG O, FOLDVIK, ANDERS
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.04.2011; Wiley-Blackwell; Wiley
• Subjects: Agnatha. Pisces; Animal and plant ecology; Animal populations; Animal, plant and microbial ecology; Aquatic ecosystems; Biological and medical sciences; Climate; climate change; competition; Dispersal; Fish; Fundamental and applied biological sciences. Psychology; General aspects; growth efficiency; Habitats; Life Sciences; Salmo trutta; Salmonidae; species distribution; thermal performance; Vertebrates: general zoology, morphology, phylogeny, systematics, cytogenetics, geographical distribution; Competition; Salmonidae; Climate; thermal performance; Competitive exclusion; species distribution; Growth; Dynamical climatology; Climate change; Vertebrata; Spatial distribution; Geographic distribution; Pisces; growth efficiency; Performance; Distribution range; competition; climate change
• ISSN: 1354-1013; 1365-2486; 1365-2486
• DOI: 10.1111/j.1365-2486.2010.02335.x

We tested the importance of thermal adaptations and energy efficiency in relation to the geographical distribution of two competing freshwater salmonid fish species. Presence-absence data for Arctic char and brown trout were obtained from 1502 Norwegian lakes embracing both temperature and productivity gradients. The distributions were contrasted with laboratory-derived temperature scaling models for food consumption, growth and energy efficiency. Thermal performances of the two species were almost identical. However, Arctic char exhibited double the growth efficiency (per unit of food) and appear to have out-competed brown trout from cold, low-productivity lakes, perhaps by scramble competition. Brown trout, for which previous reports have shown to be aggressive and dominant, have likely excluded the more energy-efficient Arctic char from relatively warm, productive lakes, perhaps by contest competition. Competitive interaction changing in outcome with lake productivity, rather than thermal performance, is likely a major determinant of the range distribution of the two species. Our study highlights the need for more focus on choice of relevant ecophysiological traits in ecological climate impact studies and species distribution modelling.