Quantcast
Climate
Measuring a bigeye tuna. NOAA

Climate Change Is Making Fish Smaller

By Marlene Cimons

Seafood lovers be warned. That delectable slab of seared tuna on your plate soon could become a lot smaller—and more scarce—thanks to climate change.

As ocean temperatures climb, many species of fish—tuna among them—likely will shrink, decreasing in size by as much as 30 percent, according to a new study published in the journal Global Change Biology.


The study confirms the authors' previous research, which showed that fish won't be able to get enough oxygen to grow if ocean waters keep heating up. Fish, as cold-blooded animals, cannot regulate their own body temperatures. When ocean waters become warmer, a fish's metabolism accelerates, and it needs more oxygen to sustain its body functions. Fish breathe through gills, organs that extract dissolved oxygen from the water and excrete carbon dioxide.

The problem is that the gills' surface area does not grow at the same pace as the rest of the fish's body—and warm water contains less oxygen than cooler water. If a fish like cod grows 100 precent larger, its gills might only grow by 80 percent or less, according to the study.

Tuna, which are fast-moving and need more oxygen may shrink by as much as 30 percent, researchers said. By contrast, brown trout, which are not as active as tuna, will only decrease in body size by about 18 percent with each degree Celsius of warming.

"There is a point where the gills cannot supply enough oxygen for a larger body, so the fish just stops growing larger," said William Cheung, director of science for the Nippon Foundation—University of British Columbia Nereus Program and a co-author of the study.

Warmer waters hold less oxygen, causing fish to shrink. Global Change Biology

Daniel Pauly, the study's lead author and a principal investigator with Sea Around Us, a University of British Columbia research initiative, agreed. He emphasized that "fish are constrained by their gills in the amount of oxygen they can extract from the water. This constraint manifests itself especially in big fish. With increasing temperatures, fish require more oxygen but get less."

The researchers first posited their principle about warming waters and fish size, which they call "gill oxygen-limitation theory," or GOLT, in a 2013 paper published in Nature Climate Change. Their conclusions were challenged by three researchers from Norway and France who claimed their models were based on "erroneous assumptions."

Cheung and Pauly responded to the criticism "by restating both the principle upon which the 2013 study was built, and by re-computing the effect of warming on shrinkage in more detailed fashion, which increased the shrinkage," Pauly said.

With a drop in maximum body size, potential fisheries production will decrease "and that will directly affect the fishing industry," Cheung said. This could result in a loss of potential catch amounting to about 3.4 million metric tons for each degree Celsius of atmospheric warming, he said.

"Some parts of the world, such as in the tropics, are going to see even larger decreases," he said. "This will have substantial impacts on the availability of fishes for people." Scientists said that fish are already shrinking.

"We are already seeing the effects and shrinking of fishes due to warming," Cheung said. "For example, colleagues in the UK analyzed long-term data of fish body size in the North Sea and found that fish stocks such as haddock and sole had decreased in maximum body size in the last few decades, and such shrinkage of size was significantly related to ocean warming in that region, even after correcting for the effects of fishing."

Moreover, oxygen-starved fish may truly end up breathless. Pauly noted that oxygen deprivation is already killing fish in the U.S. and around the world. Though, he added, "Oxygen scarcity doesn't necessarily kill fish. If it is mild, it will only reduce their growth. This is the reason why fish farmers aerate their ponds on very warm days, when the fish therein are literally gasping."

Oxygen scarcity will affect a multitude of sea creatures, not just smaller fish, but also larger species further up the food chain. "They are affected by global warming because their prey are," Pauly said.

"Basically, big fish eats small fish," Cheung said. "So, changes in body size may alter food web interactions and structure, affecting ecosystem functions and services."

Reposted with permission from our media associate Nexus Media.

Show Comments ()

EcoWatch Daily Newsletter

Sponsored
Oceans
The crew of the Greenpeace ship MY Arctic Sunrise voyage into the Great Pacific Garbage Patch document plastics and other marine debris. The Great Pacific Garbage Patch is a soupy mix of plastics and microplastics, now twice the size of Texas, in the middle of the North Pacific Ocean. Justin Hofman / Greenpeace

Teen Vogue Joined Greenpeace at the Great Pacific Garbage Patch — Here’s What They Saw

By Perry Wheeler

Throughout this year, people all over the globe united to take on plastic pollution. Greenpeace supporters have asked their local supermarkets to phase out throwaway plastics, helped us reach 3 million signatures to companies like Coca-Cola, Nestle and Unilever demanding they invest in real solutions and participated in beach cleanups and brand audits to name the worst corporate plastic polluters.

Keep reading... Show less
Climate
Pexels

Advocates Shouldn’t Be Afraid to Tell the Truth About Climate Change

By Jeremy Deaton

It has been a tough few months for climate change. In October, an international body of climate scientists declared humans have a little more than a decade to make the drastic changes needed to keep rising temperatures reasonably in check. In November, federal scientists released an equally grim assessment detailing the unprecedented floods, droughts and wildfires expected to hit the U.S. Then, this month, with the world ablaze, diplomats gathered in Poland to bicker over how much water each country should pour on their respective fires and, in some cases, whether scientists were exaggerating the size of the flames.

Keep reading... Show less
Ildar Sagdejev / Wikimedia / CC BY-SA 4.0

The Dirty Scheme to Make Americans Buy More Gasoline

By Rhea Suh

It's not often that an industry chieftain brags to investors about picking the pockets of American families with help from the White House.

That's what happened, though, after Big Oil schemed with the Trump administration last summer to ensure higher gasoline consumption—to the tune of $16 billion a year—and more climate-disrupting carbon pollution from our cars, vans and pickup trucks.

Keep reading... Show less
Energy
The planned Liberty Project is an artificial gravel island to allow oil drilling in the Arctic. Hilcorp / BOEM

Trump Administration Sued Over Controversial Arctic Drilling Project

Conservation groups are suing the Trump administration to halt construction of a controversial oil production facility in Alaska's Beaufort Sea, the first offshore oil drilling development in federal Arctic waters.

Hilcorp Alaska received the green light from the Interior Department in October to build the Liberty Project, a nine-acre artificial drilling island and 5.6-mile underwater pipeline, which environmentalists warn could risk oil spills in the ecologically sensitive area, threaten Arctic communities and put local wildlife including polar bears at risk.

Keep reading... Show less
Sponsored
Popular
AAron Ontiveroz / Denver Post / Getty Images

5 Everyday Products Contaminated With Plastic

However, the infiltration of plastics into our daily lives goes much deeper, making it hard to avoid this polluting material which will remain in our ecosystems for centuries to come.

Keep reading... Show less
Popular
Fracking waste from the Vaca Muerta shale basin in Argentina being dumped into an open air pit. Greenpeace

Indigenous Group Sues Exxon, Energy Majors Over Fracking Waste Contamination in Patagonia

A major indigenous group in the Argentine Patagonia is suing some of world's biggest oil and gas companies over illegal fracking waste dumps that put the "sensitive Patagonian environment," local wildlife and communities at risk, according to Greenpeace.

The Mapuche Confederation of Neuquén filed a lawsuit against Exxon, French company Total and the Argentina-based Pan American Energy (which is partially owned by BP), AFP reported. Provincial authorities and a local fracking waste treatment company called Treater Neuquén S.A. were also named in the suit.

Keep reading... Show less
Sponsored
Food
A Yelp event at Rip's Malt Shop in Brooklyn, New York, which serves vegan comfort food, including plant-based proteins produced by Beyond Meat and Field Roast. Yelp Inc. / Flickr / CC BY-NC-ND 2.0

Should Plant-Based Proteins be Called 'Meat'?

By Melissa Kravitz

Fried chicken, bacon cheeseburgers and pepperoni pizza aren't uncommon to see on vegan menus—or even the meat-free freezer section of your local supermarket—but should we be calling these mock meat dishes the same names? A new Missouri law doesn't think so. The state's law, which forbids "misrepresenting a product as meat that is not derived from harvested production livestock or poultry," has led to a contentious ethical, legal and linguistic debate. Four organizations—Tofurky, the Good Food Institute, the American Civil Liberties Union of Missouri and the Animal Legal Defense Fund—are now suing the state on the basis that not only is the law against the U.S. Constitution, but it favors meat producers for unfair market competition.

Keep reading... Show less
Energy
A coal-fired power plant in Jiangxi, China. chuyu / iStock / Getty Images Plus

IEA: China and India to Fuel Further Rise in Global Coal Demand in 2018

By Daisy Dunne

The IEA's Coal 2018 report finds that global coal demand grew by 1 percent in 2017 after two years of decline. The rise was chiefly driven by global economic growth, it says. Despite recent growth, demand is still below "peak" levels seen in 2014.

Demand is likely to "remain stable" until 2023, the report authors say. This is because falling demand in western Europe and North America is likely to be offset by increased demand in a host of Asian countries, including India, Indonesia and Vietnam.

Carbon Brief takes a look at the IEA's changing coal forecasts for key world regions.

Keep reading... Show less
Sponsored

mail-copy

The best of EcoWatch, right in your inbox. Sign up for our email newsletter!