Climate change may make popular seafood extinct, study finds

Heating oceans mean larger species are hungrier, threatening the future of smaller creatures, reports Jane Dalton

Scientists set up bait for fish (Nicolas Battini, CONICET)

Warming of the planet is making fish hungrier, which could wipe out popular types of seafood, researchers have warned.

As the ocean heats up, top predators will take control and gobble up smaller species, reducing their populations, scientists said.

The changes are expected to cascade down to transform other life in the ocean, threatening to disrupt balances that have existed for millennia.

In the biggest project of its kind, the researchers looked at 36 places in the Atlantic and Pacific Oceans along the coasts of the Americas, from Alaska in the north to the tip of South America.

They found the changes were greatest at higher temperatures.

The scientists left out dried squid as bait to attract fish, some open and some in protective cages.

In hotter waters, predators’ more voracious appetites left outsized marks, the experts found.

Total biomass plunged in the tropics when prey were left unprotected.

But in the coldest zones, leaving prey exposed or protected made almost no difference, suggesting predators did not pose much of a threat.

Emmett Duffy, director of Smithsonian’s Marine Global Earth Observatory network and research co-author, said: “Warmer waters tend to favour animals high in the food chain, which become more active and need more food - and it is their prey who pay for that increased activity.

“This suggests warming seas could see big shifts in the life of sensitive seabed habitats.”

Co-author Amy Freestone, of Temple University, Philadelphia, said: “This temperature threshold represents an ecological tipping point in these coastal marine ecosystems, above which predation intensity increases.

“With climate change, more coastal waters will exceed this tipping point, or warm even further, fundamentally changing how these ecosystems function.”

The scientists said what will happen at the equator, where temperatures may rise even higher than today, remains a mystery.

Lead author Gail Ashton, a marine biologist at the Smithsonian Environmental Research Centre, Maryland, said: “It has taken thousands of years to get to this state, and then suddenly we are ramping up the temperature at a much higher rate.

“And we don’t really know the implications of that temperature increase.”

Animals’ metabolism increases in hot weather, and the findings, published in the journal Science, support previous research that suggested predators are more active in the tropics.