Warren Cornwall, Anthropocene, June 15, 2022
As temperatures climb in the ocean, so do the appetites of its inhabitants. Fish living in balmy, tropical waters consistently eat more than their cold-water brethren, according to new research, a finding that points to one way climate change could alter marine ecosystems as fish grow more hungry.
“Warmer waters tend to favor animals high in the food chain, which become more active and need more food—and it’s their prey who pay for that increased activity,” said Emmett Duffy, director of the Smithsonian’s Marine Global Earth Observatory network and a leader of the research. “This suggests that warming seas could see big shifts in the life of sensitive seabed habitats.”
The oceans have become a dumping ground for much of the excess heat trapped by rising levels of greenhouse gases, absorbing an estimated 90% of the extra heat. Among other things, that has raised overall ocean temperatures to the highest ever recorded and is thought to be contributing to a surge in the number of underwater heatwaves that have baked coral reefs and triggered massive seabird die-offs.
It has long been known that a fish’s metabolism revs up as the temperature rises. Unlike mammals, the body temperature of fish adjusts to match the levels of its surroundings, and staying warmer requires burning more calories.
What was less well understood is the strength of the relationship between temperature and fish appetite across entire continents. Nor did scientists have a clear picture of how that connection shaped surrounding ecosystems.