Microplastics in fishmeal are contaminating farmed fish—impacting their health, the nutrition they provide, and leaving consumers potentially exposed.
Recent research in aquaculture, the farming of fish and other marine organisms, reveals a growing concern: farmed fish contaminated with microplastic particles by way of their feed.
"It's not possible, actually, to make plastic-free fishmeal or fish feed," marine biologist Sedat Gündoğdu said. (Credit: WorldFish/flickr)
Scientists sampled 26 fishmeal products from 11 countries and found plastics in every sample except the one. (Credit: WorldFish/flickr)
Plastic in organs<p>Studies have long documented microplastics in captured seafood. A recent <a href="https://doi.org/10.1016/j.marpolbul.2020.111681" target="_blank">literature review</a> found that an average of 60 percent of fish—198 species captured in 24 countries—contain microplastics in their organs. The types of fish most commonly used for fishmeal—all smaller fish that are lower in the food chain—tend to have very high levels of microplastics.</p> <p>But not all the plastics consumed by fish will be absorbed into their bodies. Gündoğdu said that particles larger than 130 micrometers—roughly the size of a small grain of sand—will sometimes collect in the animal's gut, but will not collect in the animal's organs or tissues. Unfortunately, Gündoğdu's team found microplastics under that size, which means some of these particles can pass the fishes' intestinal barriers and enter their organ tissues. This could lead to inflammation, smaller body sizes, and <a href="https://www.frontiersin.org/articles/10.3389/fmars.2018.00143/full#" target="_blank" rel="noopener noreferrer">injury to their gills</a>. </p> <p>Many people don't eat fish organs, <a href="https://www.dal.ca/faculty/management/sres/faculty-staff/our-faculty/tony-walker.html" target="_blank" rel="noopener noreferrer">Tony Walker</a>, an environmental scientist at Dalhousie University, told EHN. Especially in the Western world, people tend to eat only fish muscle, (fillets), he said—and right now there is not a lot of evidence showing microplastics making their way into muscle tissue. But there are still plenty of communities around the world whose diets and cuisines include whole fish. </p> <p>The toxic effects of consuming microplastics in humans are still unclear, especially in the long term. But depending on the type consumed, there is <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7068600/" target="_blank" rel="noopener noreferrer">evidence</a> that microplastics can exacerbate asthma, inflame the immune system, damage internal organs like kidneys, and even make their way to placentas of pregnant women. </p>
Decreased nutrition<img lazy-loadable="true" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNTU3MTI2My9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY0Nzg3Mzc0NX0.0uMt3ZItZIrLapcFxGJmTYW-tq2mODwEOiONrVK4wuU/img.jpg?width=980" id="853d9" class="rm-shortcode" data-rm-shortcode-id="20d2078bb67e56e4354e5a132c47caea" data-rm-shortcode-name="rebelmouse-image" data-width="1245" data-height="645" />
Feeding fish in cages, Jitra, Malaysia. (Credit: WorldFish/flickr)<p>Walker said that microplastics change the health of the fish we eat, which could impact nutrition. In one <a href="https://doi.org/10.1016/j.jhazmat.2020.123980" target="_blank">experiment</a> where trout were purposely fed microplastics, Walker and his team found that even if the particles were not absorbed in the guts of fish—meaning the plastics were all excreted—microscope analysis showed that trout cells deformed. While we don't yet fully know how ingesting plastics may impact our health, Walker said, it is certainly making our food sicker.</p> <p>As global fish consumption grows, experts cite aquaculture as a powerful tool to fight food insecurity—it now accounts for 46 percent of all fish production. In fact, fishery and aquaculture production growth has outpaced human population growth over the past 50 years, according to <a href="http://www.fao.org/3/a-i7677e.pdf" target="_blank" rel="noopener noreferrer">the UN</a>. With so many communities relying on seafood globally, ensuring that fish are safe for human consumption is imperative.</p>Studies show that microplastic-fed seafood have <a href="https://www.sciencedirect.com/science/article/abs/pii/S0269749116307278" target="_blank" rel="noopener noreferrer">lower feeding rate, body mass, and metabolism</a>. A <a href="http://www.fao.org/3/ca9229en/online/ca9229en.html#chapter-3_1" target="_blank" rel="noopener noreferrer">recent UN report</a> states that in aquaculture, a new disease emerges, spreads, and causes "major production losses approximately every three to five years." Microplastics can carry <a href="https://www.sciencedirect.com/science/article/abs/pii/S0025326X1730694X" target="_blank" rel="noopener noreferrer">fish-disease causing bacteria</a>, making an infectious disease epidemic in farmed fish populations increasingly likely.
“A plastic trap”<img lazy-loadable="true" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNTU3MTMzMS9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY3MTEwMjc2M30.c7yAYndWNl5gWOwSQyNiuZU6xkW9g_JHpx7HbCnnxaE/img.jpg?width=980" id="02a48" class="rm-shortcode" data-rm-shortcode-id="1e4c2e062e977c37a93d0b52eb908522" data-rm-shortcode-name="rebelmouse-image" alt="Farmed fish tilapia" data-width="1245" data-height="830" />
Farmed tilapia. (Credit: World Fish/flickr)<p>We know that the kinds of fish used in fishmeal are plastic-laden, so removing that fishmeal from fish feed could be effective at reducing the amount of microplastic farmed fish consume, <a href="https://oceans.ubc.ca/juan-jose-alava/" target="_blank">Juan José Alava</a>, a marine ecotoxicologist at the University of British Columbia, told EHN. "That's an important transition," he added, "because we want to protect the final consumer."</p> <p>Despite concerns from ecologists and environmental scientists, the International Fishmeal and Fish Oil Organisation (IFFO) states that "a fish-free feed concept is based on flawed thinking." IFFO's Director General, Petter Martin Johannessen, wrote in an email to EHN that removing fish from fish feed is "both uneconomic and impractical" as fish feed producers would need to add multiple new ingredients to achieve the same nutritional value. </p> <p>Johannesen added that aquaculture's continued growth means that fish feed will need to keep up, and "the mobilization of all the available feed ingredients will be crucial." Therefore, in the future, "fishmeal is not to be replaced but supplemented," he wrote. </p> <p>Unfortunately, even if removing fishmeal from fish feed became a global priority, the fish feed industry is so globally sprawled and non-homogenous that it would be a gigantic task, Gündoğdu said. And it wouldn't fully solve the issue of farmed fish eating microplastics. Gündoğdu and his team did not study other feed ingredients, like the vegetables and oils, that could also be contaminated with plastics by factory production processes. </p> <p>Even if fish do not directly consume plastic particles, there are plenty of other routes of exposure, Alava added. The nets and pens that contain farmed fish are possible sources of contaminants, as are the clothes from fishery workers. "As long as there are humans, that's a potential source for exposure to contaminants."</p> <p>When you analyze microplastic contamination, you see the story of human plastic use, said Gündoğdu. </p> <p>Everyone needs to understand that "if you use plastic, then this pollution will come back to your plate," he said. "We are in a plastic trap."</p>