Quantcast

How Nutritious Is That Fish? To Find Out, Ask Its Relatives

To predict the nutrient content of fish, a new study turned to shared evolutionary history. Oceana / Eduardo Sorensen

By Amy McDermott

Eels and anchovies don't look or act much alike. One is sinuous and shy, the other a bright flash of silver in a school of thousands. Yet the two fish are cousins, both loaded with zinc.


Related fish species—like eels and anchovies—have similar nutritional value, according to a new study in Nature Communications. Two fish can be wildly different on the outside but surprisingly similar on the inside, if they're close on the tree of life.

"There's a shared evolutionary history in the ocean," said food security scientist Bapu Vaitla, who co-led the new study at Harvard's T.H. Chan School of Public Health in Boston, with evolutionary biologist David Collar at Christopher Newport University in Newport News, Virginia.

Turns out, shared evolutionary history is a road map to the patterns of vitamins and minerals fanned through the tissues of fish worldwide. That's a juicy tidbit for researchers studying the links between fish and human health. The specific blend of nutrients in a fish determines how people are nourished when they eat that species.

Making Connections

More than 3 billion people depend on fish for about one-fifth of the animal protein they eat. It's a staple food in dozens of countries, that offers calories, protein, fats and essential micronutrients like iron, zinc, calcium and vitamin A.

Not all fish are the same, though. Cod is much lower in zinc than anchovies, while salmon and trout are fattier than flatfishes, and higher in vitamin D than mackerels. Each species has its characteristic mix of nutrients.

Knowing that mix tells scientists how fish nourish people. It's valuable information, but not cheap or easy work.

Analyzing the nutrient content of one tissue sample costs several hundred to several thousand dollars, said Oceana science adviser Chris Golden, who heads the Harvard research group responsible for the new study. It takes multiple samples, sometimes collected around the world, to build a complete nutrient profile for a species.

Nutrient profiles do exist for hundreds of fish species, but thousands are nutritionally important, Vaitla said. "We couldn't collect samples all over the world, so we needed to predict nutrient content somehow."

The species people eat can say a lot about global health. Oceana / Jon Dee

A Living Mosaic

The oceans are a patchwork of unevenly distributed nutrients. Vaitla and his research partners expected that fish with similar lifestyles, that develop in similar conditions and habitats, would probably be exposed to similar challenges and opportunities, and so be nutritionally alike.

But when the scientists looked across 371 food fish species, they found that body size, preferred habitat and other lifestyle characteristics were not good predictors of nutritional similarity. Instead, genetic relatedness turned out to be key.

"It's not totally unsurprising," said marine ecologist William Cheung of the University of British Columbia, in Vancouver, who was not involved in the new study. Evolutionary relationships click as predictors of nutrition, he said. "Sometimes in science, when someone tells you the answer, you think, ah yes, that's true, that makes sense."

Yet, Cheung said, if he had undertaken the same research, he would've tested lifestyle characteristics first, too. He and Vaitla were both surprised that body size, habitat and other lifestyle characteristics didn't seem to play a role. Vaitla hasn't ruled them out. Repeating the study with more species of fish, he said, could reveal a pattern between lifestyle characteristics and nutrition in the future.

Food for Thought

That related fish are nutritionally similar may not be surprising, but it is useful. Scientists can now predict the vitamin and mineral content of fish species without tissue samples, based instead on their evolutionary relationships.

Predictions could come in especially handy now, as many marine species relocate in response to global change. As they move, they carry their distinct mix of vitamins and minerals with them, exposing fishermen and coastal people to a new mix of nutrients in the fish they eat. When new species move in, they may have different nutritional value from the old staples, exposing communities to risk of malnutrition.

Sculpins, scorpionfishes and their relatives tend to be low in vitamin D, the new study showed. Oceana / Eduardo Sorensen

"When we're worried about things like climate change or pollution or overfishing and how its affecting human health, the question amounts to knowing the nutrient landscape out there and how these environmental changes alter that landscape," Vaitla said. "If we're able to know that, we can say things like climate change will impact the availability of iron to this extent, and for these people."

To avoid anticipated risks, communities might curb commercial fishing or set aside marine protected zones, Vaitla said. But first, they need a way to see what's coming. "Evolutionary history," he said, "gives us a shortcut to paint the nutrient landscape out there."

Sponsored
Prince William and British naturalist David Attenborough attend converse during the World Economic Forum annual meeting, on January 22 in Davos, Switzerland. Fabrice Cofferini /AFP / Getty Images

Britain's Prince William interviewed famed broadcaster David Attenborough on Tuesday at the World Economic Forum's annual meeting in Switzerland.

During the sit-down, the 92-year-old naturalist advised the world leaders and business elite gathered in Davos this week that we must respect and protect the natural world, adding that the future of its survival—as well as humanity's survival—is in our hands.

Read More Show Less
EV charging lot in Anaheim, California. dj venus / Flickr / CC BY-ND 2.0

Electric vehicle sales took off in 2018, with a record two million units sold around the world, according to a new Deloitte analysis.

What's more, the accounting firm predicts that another 21 million electric cars will be on the road globally over the next decade due to growing market demand for clean transportation, government subsidies, as well as bans on fossil fuel cars.

Read More Show Less
Sponsored
Teenager Alex Weber and friends collected nearly 40,000 golf balls hit into the ocean from a handful of California golf courses. Alex Weber / CC BY-ND

By Matthew Savoca

Plastic pollution in the world's oceans has become a global environmental crisis. Many people have seen images that seem to capture it, such as beaches carpeted with plastic trash or a seahorse gripping a cotton swab with its tail.

As a scientist researching marine plastic pollution, I thought I had seen a lot. Then, early in 2017, I heard from Alex Weber, a junior at Carmel High School in California.

Read More Show Less
Southwest Greenland had the most consistent ice loss from 2003 to 2012. Eqalugaarsuit, Ostgronland, Greenland on Aug. 1, 2018. Rob Oo / CC BY 2.0

Greenland is melting about four times faster than it was in 2003, a new study published Monday in the Proceedings of the National Academy of Sciences found, a discovery with frightening implications for the pace and extent of future sea level rise.

"We're going to see faster and faster sea level rise for the foreseeable future," study lead author and Ohio State University geodynamics professor Dr. Michael Bevis said in a press release. "Once you hit that tipping point, the only question is: How severe does it get?"

Read More Show Less
Seismic tests are a precursor to offshore drilling for oil and gas. BSEE

Finally, some good news about the otherwise terrible partial government shutdown. A federal judge ruled that the Trump administration cannot issue permits to conduct seismic testing during the government impasse.

The Justice Department sought to delay—or stay—a motion filed by a range of coastal cities, businesses and conservation organizations that are suing the Trump administration over offshore oil drilling, Reuters reported. The department argued that it did not have the resources it needed to work on the case due to the shutdown.

Read More Show Less
Brazil, Pantanal, water lilies. Nat Photos / DigitalVision / Getty Images Plus

Most people have heard of the Amazon, South America's famed rainforest and hub of biological diversity. Less well known, though no less critical, is the Pantanal, the world's largest tropical wetland.

Like the Amazon, the Pantanal is ecologically important and imperiled. Located primarily in Brazil, it also stretches into neighboring Bolivia and Paraguay. Covering an area larger than England at more than 70,000 square miles, the massive wetland provides irreplaceable ecosystem services that include the regulation of floodwaters, nutrient renewal, river flow for navigability, groundwater recharge and carbon sequestration. The wetland also supports the economies of the four South American states it covers.

Read More Show Less
Demonstrators participate in a protest march over agricultural policy on Jan. 19 in Berlin, Germany. Carsten Koall / Getty Images Europe

By Andrea Germanos

Organizers said 35,000 people marched through the streets of the German capital on Saturday to say they're "fed up" with industrial agriculture and call for a transformation to a system that instead supports the welfare of the environment, animals and rural farmers.

Read More Show Less
MarioGuti / iStock / Getty Images

By Patrick Rogers

If you have ever considered making the switch to an environmentally friendly electric vehicle, don't drag your feet. Though EV prices are falling, and states are unveiling more and more public charging stations and plug-in-ready parking spots, the federal government is doing everything it can to slam the brakes on our progress away from gas-burning internal combustion engines. President Trump, likely pressured by his allies in the fossil fuel industry, has threatened to end the federal tax credits that have already helped put hundreds of thousands of EVs on the road—a move bound to harm not only our environment but our economy, too. After all, the manufacturing and sale of EVs, hybrids, and plug-in hybrids supported 197,000 jobs in 2017, according to the most recent U.S. Energy and Employment Report.

Read More Show Less