Comment by kevinwang

for hn comment-only readers:

paper link: https://www.science.org/doi/10.1126/science.adt2981

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Editor Summary:

Body size and metabolic rate are intertwined, a factor that is especially important to understand with regard to animals that live in aquatic environments, where heat loss is related to water temperature. Payne et al. developed a method to estimate routine metabolic rate based on measures from tagged fish, and combined the estimates with published respirometry rates to create a dataset spanning the entire body size range of extant fishes. Using these data, the authors found a scaling imbalance between heat production and loss that affects especially large, mesothermic fishes in warm waters. This imbalance both explains the distribution of these fish in cooler waters and suggests a special sensitivity to warming waters. —Sacha Vignieri

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Abstract:

Body size and temperature set metabolic rates and the pace of life, yet our understanding of the energetics of large fishes is uncertain, especially of warm-bodied mesotherms, which can heavily influence marine food webs. We developed an approach to estimate metabolic heat production in fishes, revealing how routine energy expenditure scales with size and temperature from 1-milligram larvae up to 3-tonne megaplanktivorous sharks. We found that mesotherms use approximately four times more energy than ectotherms use and identified a scaling mismatch in which rates of heat production increase faster than heat loss as body size increases, with larger fish becoming increasingly warm bodied. This scaling imbalance creates an overheating predicament for large mesotherms, helping to explain their cooler biogeographies. Contemporary mesotherms face high fuel demands and overheating risks, which is a concern given their disproportionate demise during prior climate shifts.