Associations between metabolic traits and growth rate in brown trout ( Salmo trutta ) depend on thermal regime

Abstract

Metabolism defines the energetic cost of life, yet we still know relatively little about why intraspecific variation in metabolic rate arises and persists. Spatio-temporal variation in selection potentially maintains differences, but relationships between metabolic traits (standard metabolic rate (SMR), maximum metabolic rate (MMR), and aerobic scope) and fitness across contexts are unresolved. We show that associations between SMR, MMR, and growth rate (a key fitness-related trait) vary depending on the thermal regime (a potential selective agent) in offspring of wild-sampled brown trout from two populations reared for approximately 15 months in either a cool or warm (+1.8°C) regime. SMR was positively related to growth in the cool, but negatively related in the warm regime. The opposite patterns were found for MMR and growth associations (positive in warm, negative in the cool regime). Mean SMR, but not MMR, was lower in warm regimes within both populations (i.e. basal metabolic costs were reduced at higher temperatures), consistent with an adaptive acclimation response that optimizes growth. Metabolic phenotypes thus exhibited a thermally sensitive metabolic ‘floor’ and a less flexible metabolic ‘ceiling’. Our findings suggest a role for growth-related fluctuating selection in shaping patterns of metabolic variation that is likely important in adapting to climate change.

Predator-Prey Interactions between Nonnative Juvenile Largemouth Bass (Micropterus salmoides) and Local Candidate Prey Species in the Pearl River Delta: Predation Capacity, Preference and Growth Performance

“…This may be partially attributable to intragroup variation caused by predator personality. Data from wild-sampled brown trout reared under different conditions show that its standard metabolic rate was not positively correlated with growth in a warm regime [38]. It may partially explain why the difference in ADG did not result in a corresponding difference in SGR.…”

Egg incubation temperature influences the population‐specific outmigration rate of juvenile brown troutSalmo trutta

“…This may be particularly true for juvenile S. trutta incubated as embryos in warm water, as they have been shown to have lower metabolic rate and aerobic scope than those incubated in colder water (Durtsche et al, 2021). In parallel, Archer et al (2021) reported that the standard metabolic rate was lower when juveniles of S. trutta were reared at an elevated temperature. Aerobic scope is the difference between the maximum and the standard metabolic rates, and it represents the capacity of organisms to increase their aerobic metabolic rates above the maintenance level to carry out various activities, such as feeding, swimming and defence (Fry, 1971).…”

“…In parallel, Archer et al . (2021) reported that the standard metabolic rate was lower when juveniles of S. trutta were reared at an elevated temperature. Aerobic scope is the difference between the maximum and the standard metabolic rates, and it represents the capacity of organisms to increase their aerobic metabolic rates above the maintenance level to carry out various activities, such as feeding, swimming and defence (Fry, 1971).…”

Growth variation along a dispersal gradient in juvenile rainbow trout

“…The potential role of a plastic (i.e. environmentally‐induced) response to temperature or ambient food availability, however, cannot be eliminated with our study design, since ration and rearing temperature can affect subsequent growth rates (Archer et al, 2021). Ideally, dispersers (and non‐dispersers) would need to be collected immediately after their decision to emigrate to test for differences in growth or behavioural traits in common laboratory environments.…”

“…The potential role of a plastic (i.e. environmentally-induced) response to temperature or ambient food availability, however, cannot be eliminated with our study design, since ration and rearing temperature can affect subsequent growth rates (Archer et al, 2021).…”