(Image: Marje Cannon/Getty)

Fish caught off the coasts of California and Indonesia and sold in local markets have been found to have plastics and textile fibres in their guts, raising concerns over food safety.

Chelsea Rochman at the University of California Davis school of veterinary medicine and her team visited a fish market in Half Moon Bay and Princeton in California and in Makassar, Indonesia.


In California they sampled 76 fish from 12 species and one shellfish species, and in Indonesia 76 fish from 11 species. All had been caught nearby. The animals were dissected and their guts treated chemically to dissolve body tissue and reveal any plastic and fibre debris they contained.

The team found that 55 per cent of the fish species sampled in Indonesia contained human-derived debris. This included Indian mackerel, shortfin scad and silver-stripe round herring. In total, 28 per cent of the fish sampled contained the debris, with one having 21 pieces of plastic inside it.

In the US, 67 per cent of the species – including the pacific oyster – contained the debris. The species included Pacific anchovy, striped bass and Chinook salmon. A quarter of the individual fish sampled were affected.

Textile fibres made up the majority of human-made debris found in fish in the US, while plastic dominated that found in Indonesia’s fish. “I was very surprised to see such a difference in type of debris between locations,” says Rochman.

Plastic recycling

This may reflect the differences in waste management. In the US, the widespread use of waste collection systems that involve plastic recycling may explain the low levels of plastic debris, Rochman says. Indonesia, however, has less advanced waste management and often disposes of plastic waste directly into coastal regions.

In contrast, the high levels of textile fibres in the US fish probably come from the widespread use of washing machines, whose effluent is sent to wastewater treatment plants in California.

“Fibres are a ubiquitous contaminant in the effluent from wastewater treatment plants due to their small size and abundance in the waste stream. They have been found in several marine habitats and animals,” says Rochman.

This isn’t the case in Indonesia. “The location where we sampled in Indonesia does not have the advanced wastewater treatment that is prevalent in California,” says Rochman. “So the wastewater from clothes washing does not enter aquatic habitats.”

The authors say the fish may still be OK to eat as long as we avoid their guts – though they don’t exclude the possibility that some of the chemicals could move from the plastic into the flesh.

There may be other consequences of debris-laden fish, though. “If the plastics are harming fish populations it could affect food security,” Rochman says.

“This clearly shows that plastic is in our food chain,” says Pete Davison of Farallon Institute for Advanced Ecosystem Research in California. “There is now quite a bit of literature showing that a wide variety of marine species consume plastic. It is likely to be happening everywhere.”

Journal reference: Scientific Reports, DOI: 10.1038/srep14340