Researchers California and Indonesia are reporting some of the first findings of plastic debris and textile fibers in fish on consumers’ dinner plates.

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Scientists have long suspected that plastic trash eaten by fish, crabs, bivalves and other marine species may be spreading through the food web.

Researchers from the University of California, Davis, and Hasanuddin University in Makassar, Indonesia, are reporting some of the first findings of plastic debris and textile fibers in fish on consumers’ dinner plates.

About one-quarter of the fish sampled from markets in California and Indonesia contained the man-made debris, according to the study published in the online journal Scientific Reports a month ago.

The researchers also discovered a stark contrast between the types of debris found in fish from both locations. In Indonesia, they found plastic fragments. In California, a majority of the contaminants consisted of fibers from textiles.

The variations in debris types probably reflect differences in local waste-management strategies, according to the study.

In Indonesia, 30 percent of the solid waste generated by humans is discarded directly onto beaches and into rivers and drainage channels, the study said. In California, there are more than 200 wastewater-treatment plants discharging billions of liters of treated effluent just offshore.

“Even though wastewater treatment results in a reduction of many contaminants,” the study said, “synthetic fibers from washing machines can remain in sewage effluent.”

Plastic debris and fibers were found only in fishes’ guts. Therefore, humans are likely to ingest man-made debris only if fish is eaten whole, a common practice in Indonesia.

“I still eat fish — if it’s sold in the United States,” said Susan Williams, a professor with the UC Davis Bodega Marine Laboratory and co-author of the study. “That’s because we fillet fish and remove their guts.”

In the study, samples of whole fish, gastrointestinal tracts of fish and whole bivalves were collected during August and November 2014 from markets and fishermen at Half Moon Bay and Princeton, Calif., and from the Paotere fish market in Makassar.

In California, researchers processed 64 individual fish from 12 species.

They found man-made fibrous material in 29 percent of jack smelt, 30 percent of Pacific anchovies, 33 percent of yellowtail rockfish, 43 percent of striped bass, 25 percent of chinook salmon, 20 percent of blue rockfish, 60 percent of Pacific sand dabs, 9 percent of lingcod and 33 percent of Pacific oysters.