By Caroline Johnson, intern
Why do fish eat plastic?
Fish are exposed to microplastic in even the deepest depths of the ocean.
Some microplastics come from larger plastic products that break into smaller pieces over time, like polystyrene foam cups or fibers from synthetic clothing.
Plastic pellets are another major source of marine microplastic. Pellets are lentil-sized round plastics used to manufacture many products, and an estimated 445,970 tons of these pellets – equivalent to more than 210,000 average-sized vehicles – wind up in the environment every year. Once in the water, pellets and other microplastics are very difficult to clean up and can remain in the environment for hundreds or thousands of years, meaning they can threaten wildlife for centuries.
Fish eat pellets and other microplastic when they mistake it for food (pellets look like fish eggs, which some species eat), when plastic is mixed in with their food or if they eat other fish that have consumed plastic. Fish consume microplastic at all levels of the food chain, from tiny organisms like plankton to small fish to predatory fish at the top of the food chain.
How common is plastic in fish?
As of 2016, 220 animal species have been found to ingest microplastic, including fish–up nearly 70% since 1977.
Over 90% of US seafood is imported from regions with significant plastic waste leakage and pollution. California in 2015 found that a quarter of all commercial fish processed in the state is known to contain microplastics. Other studies have found even higher rates of plastic contamination in fish. A new study from Portland State University in Oregon found microplastics in 99 percent of samples from six common seafood species. Another study found microplastics in 100 percent of Atlantic mackerel, 91 percent of European anchovy, and 40 percent of European hake (Cornish salmon) samples.
A different study found microplastics in 42 percent of sampled European seabass.
Are microplastics harmful to fish?
Microplastics unleash a slew of adverse health effects on fish, crustaceans, and mollusks.
- Cell damage: Microplastics cause damage to a cell’s DNA, which can cause mutations and diseases like cancers to be passed on to future generations.
- Oxygen molecule imbalance: Microplastics cause a harmful imbalance of oxygen molecules which can lead to reduced growth rate, increased susceptibility to disease, reproductive problems, tissue damage, and impaired immune function.
- Gut damage and starvation: After a fish consumes microplastic, much of it stays in the GI tract and triggers false signals of fullness to the brain. Plastic can also cause intestinal obstruction or physical injury, which can lead to death.
- Gills: Microplastics in the gills decrease respiratory efficiency, preventing fish from getting enough oxygen (a condition known as hypoxia). Physical damage to the gills from broken plastic also increases the probability of infections. Both hypoxia and gill damage can kill fish.
Which fish are at risk?
Scientists are still determining which species of fish are most at risk from plastic pollution. Some studies have shown that smaller organisms like shrimp and small fish like herring ingest more human-made contaminants like microplastics and microfibers, as these filter-feeders take in anything that’s floating in the water column just below the surface. Another study suggests that generalist or carnivorous fish species that feed on smaller fish have a higher chance of nurdle-specific exposure than narrow-dieted species. What’s clear is that microplastics harm many kinds of fish.
Microplastics have been identified in species such as the Pacific United States’ pink shrimp, pink snapper of southeastern Australia, zebrafish of Asia, and the crucian carp fish of Europe and Asia.
Do the microplastics in fish affect humans?
Microplastics and their even smaller cousins, nanoplastics, have been detected throughout the human body, including human brains, blood and breast milk. Since microplastics have been found in the edible tissue of many fish species, fish consumption is one possible source of microplastic in humans. Fish consumed whole are more likely to expose microplastics to humans.
One study estimates that an adult who eats the recommended one to four servings of fish per week consumes between 518 and 3,078 microplastic pieces per year.
Microplastics pose multiple threats to human health, including the functioning of our lungs, gut and reproductive systems.
Volunteers look for plastic pellets in local waterways
What to do about microplastic in fish
Since microplastics are found in drinking water and other foods, just limiting your fish intake won’t solve the problem, for you or the fish. Instead, we need to reduce the amount of microplastic getting into the environment in the first place.
First, we should prevent the dumping and spilling of plastic pellets (also known as nurdles), one of the largest sources of microplastic. You can see if plastic pellets are a problem in your local waterways by going on a nurdle hunt.
Second, you can reduce your own use of plastic, especially single-use plastics that may only be used for five minutes but pollute our oceans for centuries, by:
- Bringing reusable bags for your shopping.
- Toting a reusable water bottle around with you.
- Using reusable containers and utensils for food.
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Authors
Lisa leads Environment America’s work for a greener, healthier world. She also directs The Public Interest Network’s Washington, D.C., office and operations. A pragmatic idealist, Lisa has helped win billions of dollars in investments in clean energy and transportation and developed strategic campaigns to protect America’s oceans, forests and public lands. Lisa is an Oregonian transplant to the Capital region, where she loves hiking, running, biking, and cooking for friends and family.
