Fish adopt unique survival strategies in the warmest waters on earth

Some fish species in the Arabian Gulf's coral reefs are more resilient to climate change than previously thought.

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The warming of our oceans is poised to have a significant impact on marine life and the fishing industry, potentially disrupting entire ecosystems and the economic structures that rely on these environments. According to current scientific models, coral reef fishes could shrink by 14-39% in size by 2050 due to limitations in oxygen supply as they grow larger and rising temperatures driven by climate change.

This challenges the widely-held belief that limited oxygen supply in larger fishes is the main cause of smaller fish in warmer waters, known as the “shrinking of fishes phenomenon.” The observed species did not conform to this pattern, suggesting that there are other contributing factors.

A recent study of coral reef fish in the Arabian Gulf challenges these predictions. A team of researchers has discovered surprising adaptations in the metabolism and swimming abilities of these fish that enable them to thrive in the extreme temperatures of the Arabian Gulf. The team was led by John Burt, Co-Principal Investigator at The Mubadala Arabian Center for Climate and Environmental Sciences (ACCESS) at NYU Abu Dhabi, and Jacob Johansen, Associate Research Professor at the Hawaii Institute of Marine Biology.

Contrary to expectations, these fish have shown a remarkable ability to maintain efficient oxygen supply and high performance even in elevated temperatures, defying the theoretical predictions of reduced size due to metabolic limitations.

The study introduces a new theory suggesting that the reduction in fish sizes and their ability to survive in increasingly warm oceans may be more closely linked to an imbalance between the energy fish species can obtain and the energy they need to sustain themselves.

The researchers conducted a study published in the journal Nature Communications, in which they examined the ability of two different fish species, Lutjanus ehrenbergii and Scolopsis ghanam, to survive in the high temperatures of the Arabian Gulf compared to those living in the cooler conditions of the nearby Gulf of Oman.

Their main objective was to identify the specific characteristics that enable reef fishes in the Arabian Gulf to thrive in conditions with summer water temperatures similar to projected worst-case ocean warming scenarios for many tropical coral reefs globally by 2100.

“The hottest coral reefs in the world are an ideal natural laboratory to explore the future impact of rising water temperatures on fish,” said John Burt. “Our findings indicate that some fish species are more resilient to climate change than previously understood and help explain why smaller individuals are evolutionarily favored at high temperatures. This has significant implications for our understanding of the future of marine biodiversity in a continuously warming world.”

Journal reference:

  1. Jacob L. Johansen, Matthew D. Mitchell, Grace O. Vaughan, Daniel M. Ripley, Holly A. Shiels & John A. Burt. Impacts of ocean warming on fish size reductions on the world’s hottest coral reefs. Nature Communications, 2024; DOI: 10.1038/s41467-024-49459-8

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