Quantcast
Environmental News for a Healthier Planet and Life

Help Support EcoWatch

Climate Change Is Making Fish Smaller

Popular
Climate Change Is Making Fish Smaller
Measuring a bigeye tuna. NOAA

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.

A graphic shows how Rhoel Dinglasan's smartphone-based saliva test works. University of Florida

As the world continues to navigate the line between reopening and maintaining safety protocols to slow the spread of the coronavirus, rapid and accurate diagnostic screening remains critical to control the outbreak. New mobile-phone-based, self-administered COVID-19 tests being developed independently around the world could be a key breakthrough in making testing more widely available, especially in developing nations.

Read More Show Less

EcoWatch Daily Newsletter

A meteorologist monitors weather in NOAA's Center for Weather and Climate Prediction on July 2, 2013 in Riverdale, Maryland. Mark Wilson / Getty Images

The Trump White House is now set to appoint two climate deniers to the National Oceanic and Atmospheric Administration (NOAA) in one month.

Read More Show Less

Trending

A plastic bag caught in a tree in New Jersey's Palisades Park. James Leynse / Stone / Getty Images

New Jersey is one step closer to passing what environmental advocates say is the strongest anti-plastic legislation in the nation.

Read More Show Less

Did you know that nearly 30% of adults do, or will, suffer from a sleep condition at some point in their life? Anyone who has experienced disruptions in their sleep is familiar with the havoc that it can wreak on your body and mind. Lack of sleep, for one, can lead to anxiety and lethargy in the short-term. In the long-term, sleep deprivation can lead to obesity, diabetes, and cardiovascular disease.

Fortunately, there are proven natural supplements that can reduce insomnia and improve quality sleep for the better. CBD oil, in particular, has been scientifically proven to promote relaxing and fulfilling sleep. Best of all, CBD is non-addictive, widely available, and affordable for just about everyone to enjoy. For these very reasons, we have put together a comprehensive guide on the best CBD oil for sleep. Our goal is to provide objective, transparent information about CBD products so you are an informed buyer.

Read More Show Less
Speaker of the House Nancy Pelosi (D-CA) talks to reporters during her weekly news conference at the U.S. Capitol Visitors Center on Sept. 18, 2020 in Washington, DC. Chip Somodevilla / Getty Images

The House of Representatives passed a sweeping bill to boost clean energy while phasing out the use of coolants in air conditioners and refrigerators that are known pollutants and contribute to the climate crisis, as the AP reported.

Read More Show Less

Support Ecowatch