Pacific Ocean trash patch mystery: How many fish eat plastic?

Small fish living in a region of the Pacific Ocean where floating trash collects in a huge, slowly swirling bowl eat as much as 24,000 tons of plastic waste each year, scientists have found.

The region, dubbed the Great Pacific Garbage Patch, is double the size of Texas. It contains plastic flotsam and jetsam – toys, cups, wrappers, and bottles – that slowly degrade under sun and wave action into smaller and smaller fragments, until fish often mistake them for food.

Because of a problem in collection methods, prior studies tended to exaggerate the amount of plastic that fish consumed, as well as the percentage of fish consuming plastic. Now, the new study by the Scripps Institution of Oceanography shows that nearly 1 in 10 fish in the region had plastic in their stomachs.

Specifically, the new study examined 141 fish across 27 species, and scientists found that 9.2 percent had ingested plastic debris – mostly broken-down tidbits smaller than a person's fingernail.

Small fragments of plastic could leach toxins into the fish, which is widely thought to stunt their growth, alter their reproduction, or even kill them. But this study did not focus on toxic effects or the mortality of fish eating plastic. Still, these questions remain: To what degree does plastic, and its toxins, migrate up the food chain? When small fish with plastic inside are eaten by larger fish, how much impact does this have on the large predators – or even on humans who may eat them?

"These fish have an important role in the food chain because they connect plankton at the base of the food chain with higher levels," Rebecca Asch, co-author of the new study, said in a statement. "We have estimated the incidence at which plastic is entering the food chain and I think there are potential impacts, but what those impacts are will take more research."

Previous studies found plastic in the stomachs of up to 50 percent of the fish that were netted. But the fish had a tendency to eat the plastic bits that were captured with them in the net, thus inflating the results. The Scripps researchers used varying types of nets, depths, and trawling methods to correct for this tendency.

Even so, the Scripps researchers said their measurements represented "an underestimate of the true ingestion rate because a fish may regurgitate or pass a plastic item, or even die from eating it," said Peter Davison, a co-author of the study, in a statement. "We didn't measure those rates, so our nine percent figure is too low by an unknown amount."

Most fish in the study were a species commonly known as lanternfish because of its luminescence. Although lanternfish are at depths of 650 to 3,200 feet during the day, they swim near the surface at night to feed on plankton, but they often gulp plastic by mistake.

Most of the plastic floating in the Great Pacific Garbage Patch is so diffuse that it cannot actually be identified as a "patch" from satellites overhead. Instead, the patch is a zone just beneath the surface where the number of plastic debris particles is far higher than average.