(Photo: Tomohiro Ohsumi/Getty Images)

Seafood plays a traditional and important dietary role in many parts of the world, particularly in developing island nations and coastal communities. In these places, fish, and shellfish can exceed 50 percent of residents' total animal protein intake, according to the United Nations Food and Agriculture Organization. Worldwide, seafood accounts for 17 percent of the animal protein and 6.7 percent of all the protein consumed annually.

Yet seafood stocks are increasingly threatened by climate change, overfishing, plastic pollution, and habitat loss. The growing demand for seafood is also intensifying destructive fishing practices and the bycatch of marine animals. That has led some marine scientists to stop eating seafood altogether and advise others to consider doing the same, or at least think more about the fish they're eating.

Legendary oceanographer Sylvia Earle put the spotlight on the issue when she spoke out in 2014 against consuming marine animals. "We have seen such a sharp decline in the fish that we consume in my lifetime that I personally choose not to eat any," she said in an interview that year. "In the end, it's a choice." Earle also said that the accumulation of toxins in the bodies of marine animals is another reason she avoids eating seafood.

Other marine scientists have opted not to eat the animals they study. Last year Laura McDonnell, an aquatic respiratory ecology research assistant at McGill University in Montreal, published an essay in The Walrus outlining why she has stopped eating fish. Like Earle, she said she is concerned about the possible health risks of eating contaminated fish. "Over the past nine years, I've seen, read and heard about what happens to fish before it ends up on our plates," McDonnell wrote. "And now, whenever my friends order sushi takeout, or my dad enjoys his breaded fish fillets, or even when my cat eats his 'seafood medley' dinner, I get nervous—not just for the fish, but also for my loved ones."

She said that, while some people criticized her writing as extreme, she didn't intend for the essay to come across as alarmist. "At the end of the day, the article wasn't meant to shame or get people to throw out all their fish and stop eating it immediately—it was written so that discussions could begin on these issues," she said in an interview.

McDonnell emphasized that many people live in large cities far from coastlines, causing a human disconnect from the marine ecosystems that people rely on for food and other resources. Besides making people think about how fish might affect human health, her essay, she said, was intended to make people consider the implications of their actions that harm fish, like using single-use plastic bags.

"If the plastic pollution issue is so massive that there are multiple enormous floating garbage patches in oceans and marine animals at many levels of the trophic web are ingesting it, what does that say about our lifestyle as humans?" McDonnell said. "What needs to change?"

Lori Marino, president of the Whale Sanctuary Project and a neuroscientist who focuses on marine mammals, has also given up eating fish. She said that it's the human-ocean disconnect that leads to human lifestyles that can harm ocean animals. She pointed to the case of United States Pacific Northwest salmon, which are dwindling in number largely due to dams that interfere with the journey of spawning salmon from streams to the sea and back. As a result, the region's resident killer whale population, which eats only fish, has suffered a precipitous population decline.

"We are competing with other aquatic animals, such as marine mammals, for prey when it is totally unnecessary," Marino said. "And in many cases, we are causing other animals to be endangered because we are taking all of their food."

Marino, unlike McDonnell and Earle, is vegan, meaning she does not consume any animal foods—no fish, meat, eggs, or dairy. She said that, while many vegetarians are OK with eating fish, she chooses not to because, just like land animals, they are "sentient beings and we do not need to eat them to live healthy lives." Indeed, scientists have, in recent years, collected data showing that fish are sentient and feel pain. Marino said another reason she avoids eating fish is due to widespread ocean pollution.

To be clear, health experts say eating many kinds of seafood regularly can be part of a healthy diet. But some fish are better choices than others. Eating sustainably caught fish and shellfish that are low in mercury—or that are sustainably farmed—can provide a good source of protein and omega-3 fatty acids to the diets of most healthy people, according to the U.S. Environmental Protection Agency.

"Fish eating is, for me, an ethics issue, but it is difficult to disentangle that part with the sustainability component," Marino said. "Conservation is an ethical issue for me as well."

This article originally appeared on Oceans Deeply, and you can find the original here. For important news about our world’s oceans, you can sign up to the Oceans Deeply email list.