North Pacific fish are eating tens of thousands of tons of plastic debris, say researchers from the Scripps Institution of Oceanography at UC San Diego.
The team found evidence of plastic waste in the stomachs of over nine percent of fish collected during their voyage to the North Pacific Subtropical Gyre - the so-called Great Garbage Patch.
Based on this, they estimate that fish in the intermediate ocean depths of the North Pacific are ingesting plastic at a rate of roughly 12,000 to 24,000 tons per year.
"These fish have an important role in the food chain because they connect plankton at the base of the food chain with higher levels," says resewarcher Rebecca Asch.
"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."
Of the 141 fishes, spanning 27 species, dissected in the study, the researchers found that 9.2 percent of the stomach contents of mid-water fishes contained plastic debris, primarily broken-down bits smaller than a human fingernail. The majority were so small their origin couldn't be determined.
"About nine percent of examined fishes contained plastic in their stomach. That is an underestimate of the true ingestion rate because a fish may regurgitate or pass a plastic item, or even die from eating it," says Peter Davison.
"We didn't measure those rates, so our nine percent figure is too low by an unknown amount."
Previous studies on fish and plastic ingestion have examined the phenomenon in nets - where the presence of platsic within the net might lead to artificially high rates of ingestion.
"This study clearly emphasizes the importance of directly sampling in the environment where the impacts may be occurring," said James Leichter, a Scripps associate professor of biological oceanography.
"We are seeing that most of our prior predictions and expectations about potential impacts have been based on speculation rather than evidence and in many cases we have in fact underestimated the magnitude of effects."