There’s Probably Garbage in Your Fish

In Indonesia and the United States, fish are contaminated with human debris. 

Published November 2, 2015

Human rubbish, especially plastic, is increasingly finding its way into the ocean, and into fishes’ bellies. But in a twist of not-so-delicious irony, that garbage seems to also be finding its way onto our own dinner plates—trapped in the stomachs of fish. In new research, scientists report how they found human trash, including plastic and textile fibers, in a quarter of fish purchased from markets in the United States and Indonesia.

Though the prevalence of trash in the ocean is well known, few researchers have specifically looked for it in animals meant for human consumption. In their study, a team of researchers led by conservation biologist Chelsea Rochman describe how they purchased 76 fish from a market in Makassar, Indonesia, and 64 from local fishermen and fish markets in Half Moon Bay and Princeton, California.

In the digestive tracts of 28 percent of the Indonesian fish and 25 percent of the Californian ones, they found human trash. There was rubbish in 6 species of fish out of 11 purchased in Indonesia, and in 8 of 12 species sampled in California. Overall, three times as many pieces of debris were recovered from fish in Indonesia, with the number of pieces per fish ranging from 0 to 21, compared with 0 to 10 in California. The researchers didn’t count trash smaller than 0.5 millimeters.

Though the rates of contamination were similar, the types of trash were different: all of the fragments recovered from the guts of Indonesian fish were plastic, while 80 percent of the trash in Californian fish were textile fibers.

“The results seem to be in line with differences in waste management practices,” says Rochman.

In Indonesia, waste management is poor and rubbish is often dumped along the coast, and into rivers and drainage channels. But California has its own issues: roughly 200 wastewater treatment plants discharge into coastal waters, pumping fibers from washing machines into the sea. Some of these fibers are eaten by fish, and some of these fish are caught in fishermen’s nets.

This kind of finding is no longer a surprise, says Kara Lavender Law, an oceanographer who studies marine debris. “We use plastics in nearly every aspect of our daily lives, so it should not be surprising that we find bits of this essentially non-biodegradable material everywhere we look.”

Plastic is ubiquitous, including in the fish at the market. Yet whether the waste in a fish’s gut makes it into yours depends on how the fish is prepared, says Rochman. You would only ingest the plastics and fibers in a fish’s gut if you eat it whole—a practice that is common in Indonesia, or in American cuisine with smaller fish such as anchovies.

Much more research is needed, says Rochman, to understand the actual health risks posed by this plastic—both from consuming it directly, and from the toxins that may leach into the meat. She thinks the health benefits of eating seafood outweigh potential risks, but does stay away from long-lived animals at the top of the food chain, such as sharks and swordfish, where contaminants might concentrate.

While researchers continue to look at the risks posed to marine life by human debris, it’s also important to consider that at least some of this trash will make its way right back to shore.