High fuel demand and overheating risk challenge mesothermic fishes in warming oceans
Nicholas Payne, Trinity College Dublin, The University of Dublin
December 20, 2024 | 11h00 | Hybrid Seminar (Zoom Link: https://videoconf-colibri.zoom.us/j/98714568729)
Body size and temperature set metabolic rates and the pace of life, but the energetics of large fishes is uncertain, especially for the warm-bodied mesotherms, many of which heavily influence the structure of oceanic food webs. We developed a novel approach to estimate metabolic heat production in fishes, enabling tests of how routine energy expenditure scales with size and temperature from tiny 10-mg larvae up to three-tonne mega-planktivorous sharks. We found mesothermic fish use ~ 5 times more energy than similarly sized ectotherms, and uncovered a scaling mismatch whereby large fish produce heat at a faster rate than they lose it, becoming increasingly warm bodied. This heat imbalance creates an overheating predicament for large mesotherms, helping explain their common reliance on cooler ocean habitats. High fuel demands and overheating risks will challenge contemporary mesotherms, and likely contributed to their disproportionate demise during prior oceanic regime shifts.
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