Warming Waters are Forcing Cold Water Fish Into New Territories — and It Could Spell Trouble For Marine Ecosystems
Ocean temperatures are rising, and fish species are migrating to adapt to warmer waters, according to a report in the Annual Review of Marine Science.
Almost all of the increase in oceanic temperature changes has occurred in the past 50 years, according to the National Oceanic and Atmospheric Administration (NOAA). In 2023, the global ocean temperature was the warmest on record. But in 2024, temperatures increased, and the record was broken for the second year in a row, according to State of the Climate, a special report by the American Meteorological Society.
Many fish simply can’t handle the heat.
“Marine species are very temperature sensitive, more so than what we see on land,” James W. Morley, an assistant professor of biology at East Carolina University and an assistant scientist at the Coastal Studies Institute, told Discover.
As a result, fish are migrating to cooler waters. It’s not that they are moving permanently; they are shifting their range, particularly during times of reproduction.
“There will be winners and losers,” Morley said.
Climate advocates warn that carbon emissions need to be curbed to mitigate migration.
Read More: Poop of the Ocean’s Tiniest Organisms Could Combat Climate Change
Impacts Migrating Fish Have On Local Populations
For the Atlantic Ocean along the east coast of the U.S., scientists used historical datasets to develop computer models that predict where species will move, according to a report in PLOS One.
“A lot of people are envisioning that individual fish are moving northward to settle into new areas. While that does happen, probably the most important mechanism in species range shift involves species reproduction. Their offspring are being redispersed,” Morley said.
For example, shrimp near the North Carolina and South Carolina coasts are a subtropical species. But as waters have warmed, they have headed to the mid-Atlantic.
“Ten or fifteen years ago, they started moving into Chesapeake Bay,” Morley told Discover. “Now Chesapeake Bay has become an important nursing ground for one or two species [of shrimp].”
But what will it mean for the species already in that area?
In some areas, such as the Chesapeake Bay, scientists are still studying the implications.
“In that case, we don’t know as much because it’s kind of an experiment playing out in real time,” Morley said.
But in other areas, negative consequences are more apparent.
“In the Gulf of Maine, longfin squid have been shifting more into the Gulf of Maine. They are eating a lot of northern shrimp, which is more of a cold-water species, and that’s having a negative impact on the shrimp there. It’s harming the species that were already there,” Morley said.
Helping to Curb Unnecessary Migration
The idea that the ocean temperatures were permanent has long been disproved. But many scientists argue that achieving net-zero carbon emissions will help prevent the worst of global warming’s impact on the oceans, according to the Intergovernmental Panel on Climate Change.
Currently, the oceans are predicted to rise by 2 degrees Celsius by the end of the century, according to a study in Deep Sea Research Part II: Topical Studies in Oceanography.
“If we fail to curb carbon emissions, we’ll see incredibly large changes in terms of marine ecosystems,” Morley said.
Countries that signed the Paris Agreement on climate change have pledged to reduce emissions to mitigate the overall global temperature. For marine life, such a change could be a lifesaver.
“Even one degree makes a difference,” Morley said.
Read More: Climate Change May Be Making Our Days A Little Longer — Here’s How We Know
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
