Rainbow trout in seasonal environments: phenotypic trade‐offs across a gradient in winter duration

• Published in: Ecology and evolution Vol. 5; no. 21; pp. 4778 - 4794
• Main Authors: Lea, Ellen V., Mee, Jonathan A., Post, John R., Rogers, Sean M., Mogensen, Stephanie
• Format: Journal Article
• Language: English
• Published: England John Wiley & Sons, Inc 01-11-2015; John Wiley and Sons Inc
• Subjects: Adaptation; Animal behavior; Biodiversity; Bioenergetics; Body size; Elevation; elevation gradient; Energy; energy deficit; Energy storage; Fisheries; Fitness; Food; Foraging behavior; Growth rate; Ice cover; Lakes; life‐history; metabolic demands; Metabolic rate; Metabolism; Oncorhynchus mykiss; Original Research; overwinter survival; Physiology; Predation; Reproductive fitness; Respiration; Seasons; Starvation; Strains (organisms); Survival; trade‐offs; Trout; Winter; British Columbia Canada; Canada; life‐history; trade‐offs; Bioenergetics; elevation gradient; overwinter survival; energy deficit; metabolic demands
• ISSN: 2045-7758; 2045-7758
• DOI: 10.1002/ece3.1636

Survival through periods of resource scarcity depends on the balance between metabolic demands and energy storage. The opposing effects of predation and starvation mortality are predicted to result in trade‐offs between traits that optimize fitness during periods of resource plenty (e.g., during the growing season) and those that optimize fitness during periods of resource scarcity (e.g., during the winter). We conducted a common environment experiment with two genetically distinct strains of rainbow trout to investigate trade‐offs due to (1) the balance of growth and predation risk related to foraging rate during the growing season and (2) the allocation of energy to body size prior to the winter. Fry (age 0) from both strains were stocked into replicate natural lakes at low and high elevation that differed in winter duration (i.e., ice cover) by 59 days. Overwinter survival was lowest in the high‐elevation lakes for both strains. Activity rate and growth rate were highest at high elevation, but growing season survival did not differ between strains or between environments. Hence, we did not observe a trade‐off between growth and predation risk related to foraging rate. Growth rate also differed significantly between the strains across both environments, which suggests that growth rate is involved in local adaptation. There was not, however, a difference between strains or between environments in energy storage. Hence, we did not observe a trade‐off between growth and storage. Our findings suggest that intrinsic metabolic rate, which affects a trade‐off between growth rate and overwinter survival, may influence local adaptation in organisms that experience particularly harsh winter conditions (e.g., extended periods trapped beneath the ice in high‐elevation lakes) in some parts of their range.
Survival through periods of resource scarcity depends on the balance between metabolic demands and energy storage. In rainbow trout, we did not observe a trade‐off between growth and predation risk related to foraging rate, nor did we observe a trade‐off between growth and storage. Our findings suggest that there may be a trade‐off between growth rate and starvation resistance mediated by metabolic rate.