Great White Sharks and Tuna Face Overheating Risk as Oceans Warm

A groundbreaking study, spearheaded by researchers at Trinity College Dublin in collaboration with Professor Edward Snelling from the University of Pretoria's Faculty of Veterinary Science, sheds critical light on the vulnerability of some of the ocean's most iconic predators to climate change. The findings, published in the prestigious journal *Science*, reveal that warm-bodied fish, or mesotherms, such as great white sharks, mako sharks, basking sharks, and various tuna species, are far more energy-intensive than previously understood. This heightened metabolic rate, nearly four times that of cold-blooded fish of similar size, places them in a precarious position as global ocean temperatures continue to rise.

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Great white sharks, tuna and other warm-bodied fish burn nearly four times more energy than cold-blooded species, leaving them increasingly vulnerable as rising ocean temperatures shrink their habitats, a new study has found

The research highlights a phenomenon the scientists term "double jeopardy." These high-performance predators already operate with substantial baseline energy demands. Compounding this is the reality of a rapidly warming ocean, which not only shrinks their suitable habitats but also impacts food availability. This dual pressure could force these species to migrate towards cooler, polar regions, fundamentally altering marine ecosystems and food webs. Professor Snelling aptly summarized the situation: "This research shows that being a high-performance predator in the ocean comes at a greater cost than we previously appreciated. As the oceans warm, these species are being pushed closer to their physiological limits, which could have consequences for where they can live and how they survive."

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This places them in what the researchers describe as “double jeopardy”: high baseline energy demands combined with a rapidly warming ocean and declining food availability.

From the perspective of the Mail & Guardian in South Africa, this study carries particular weight due to the involvement of Professor Snelling from the University of Pretoria. The research underscores the global nature of climate change impacts and the critical role of scientific collaboration across continents. The focus on large, charismatic marine animals like great white sharks resonates with a public that often feels a connection to these species. The findings serve as a stark reminder that the consequences of greenhouse gas emissions extend far beyond terrestrial concerns, directly threatening the health and stability of marine environments that are vital to global biodiversity and, indirectly, to human well-being. The study's methodology, using biologging devices to measure metabolic rates in free-swimming fish, represents a significant advancement in oceanic research, offering a more accurate understanding of these animals' energetic costs and their susceptibility to environmental changes.

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Ocean temperatures are warming because greenhouse gas emissions trap heat in the atmosphere, with the oceans absorbing most of the excess heat.