March 31, 2020 — For centuries, fishers in Narrangansett, R.I., have plied the waters of the northwestern Atlantic for herring—small, schooling fish that are also a staple for ocean predators. But as climate change warms the world’s seas, the herring these fishers rely on are vanishing at the southern end of their range and turning up more often at its northern edges. This situation is playing out in ocean waters the world over: concentrations of marine animal populations have been shifting away from the equator and toward the poles during the course of the past century, according to one of the most comprehensive analyses of marine species distributions to date. These movements could wreak havoc on food webs and endanger the livelihoods of people who depend on key fisheries, researchers say.
“These are changes that are actually taking place in established, local communities,” says study co-author Martin Genner, a fish ecologist at the University of Bristol in England. “It’s about changes in the species people know in their environment, in the abundance of the stuff that’s already there.”
The study, published Thursday in Current Biology, analyzed how the quantity of 304 marine species—including tiny phytoplankton, seagrass, algae, fish, reptiles, marine mammals, and seabirds—has changed over the past century. The researchers gathered data from 540 abundance measurements taken in oceans around the world since the late 1800s, from the Arctic Ocean north of Alaska and through the equator to the Southern Ocean off of Antarctica. They found that studies conducted nearer to the poles were more likely to show increases in a species’ population and that those conducted nearer the equator were more likely to show a decline.