A study published by the journal Science, in which the University of Granada participated, reveals that species such as tuna and great white sharks could suffer from overheating as ocean temperatures rise
A research paper recently published by the journal Science warns that large mesothermic fish such as tuna, basking sharks, and great white sharks face high energy demands and a growing risk of overheating due to rising ocean temperatures. The study, in which University of Granada researcher Ignacio Peralta Maraver participated, analyzes how body size, each species’ thermal strategy, and global warming determine their current distribution and future vulnerability, and even provides new insights into the extinction of past species such as the megalodon.
The researchers distinguish two major groups of fish based on their ability to regulate body heat. On one hand, strict ectotherms, whose body temperature depends directly on that of the water, and on the other, mesotherms, which generate and retain part of their internal heat. The latter, which include some of the best-known and largest species, require much more energy than ectotherms of similar size and, furthermore, have great difficulty dissipating heat.
The research team has developed and validated an innovative technique to estimate the metabolic demand of a wide variety of bony and cartilaginous fish based on their body size and thermal strategy. This breakthrough is particularly significant because it allows for the study of species whose metabolic rate was practically impossible to measure directly in the laboratory.
Larger size, more heat, and less ability to cool down
Thanks to these estimates, the authors have been able to determine that, as mesothermic fish increase in size, they generate heat faster than they can lose it. This metabolic mismatch leads to an increased risk of overheating. This phenomenon explains why, in today’s oceans, many of these species are concentrated in cold waters, high latitudes, or deep zones, where the temperature allows them to compensate for their high energy demands. The researchers have verified that their model accurately reproduces the actual global distribution patterns of large marine fish.
The study’s objective not only looks to the future but also proposes a new explanation for species extinctions that occurred millions of years ago. The authors suggest that giants like the megalodon may have gone extinct after becoming trapped in a lethal combination: an extremely high energy requirement, a limited ability to dissipate heat, and thermal limits that became unsustainable when ocean conditions changed. In this way, the research effectively links the physiology, geographic distribution, and extinction of large fish on a global scale.
Key Insights for Conservation and Fisheries Management
The study’s findings enable us to anticipate which species will be most vulnerable to ocean warming, which is essential for designing conservation strategies based on physiological mechanisms rather than just current observations. They also help predict the migration of species of high ecological and fisheries value toward cooler waters, thereby improving the management of fishery resources in the context of climate change.
The study also provides tools to anticipate profound changes in the structure of ocean ecosystems, protect iconic species such as the great white shark, tuna, and whale shark, and reduce the risk of population collapse in the face of global warming.
Bibliographic reference (full text of the study)
Payne N.L., Snelling E.P., Peralta-Maraver. I., Cade D.E., Chapple T.K., McInturf A.G., Watanabe Y.Y., Sims D.W., Nuno Queiroz N., da Costa I., Sousa L.L., Goldbogen J.A., Dolton H.R., Jackson A.L. (2026). Mesothermic fishes face high fuel demands and overheating risk in warming oceans. Science. IN PRESS.
DOI: 10.1126/science.adt2981
Images
Images 1 and 2. The great white shark is one of the large mesothermic fishes facing high energy demands and a growing risk of overheating due to rising ocean temperatures.
(Photos: Andrew Fox)
Contact
Ignacio Peralta-Maraver
Department of Ecology
Phone: 958241000 ext. 20079.
Email: peraltamaraver@ugr.es