Discarded plastic gets eaten by fishes

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Plastic debris floating in the world's oceans is not only unsightly, it is also being eaten by fishes, according to a study published in a recent issue of the journal Marine Pollution Bulletin.

Christiana Boerger and coauthors made this startling discovery after studying the gut contents of fish caught in the North Pacific Central Gyre (NPCG).  

The NPCG is the site of the notorious Great Pacific Garbage Patch, an exceptional example of marine pollution consisting of a high concentration of floating plastic, chemical sludge and other items of debris trapped by the currents of the NPCG.

Most of the debris consists of small plastic particles suspended at or just below the surface. Although its existence is undoubted, the size of the Great Pacific Garbage Patch is debatable, with estimates ranging from 700,000 square kilometres to as much as 5.8 million square kilometres.

The authors collected and examined the gut contents of 670 fishes from a series of trawls carried out in the Great Pacific Garbage Patch.

These 670 fish consisted of six species: the Bigfin lanternfish (Symbolophorus californiensis), Golden lanternfish (Myctophum aurolaternatum), Loweina interrupta, Reinhardt’s lanternfish (Hygophum reinhardtii), Indo-Pacific snaggletooth (Astronesthes indopacifica) and Pacific saury (Cololabis saira).

The authors found plastic pieces in the guts of approximately 35% of the fishes examined, with some fishes having as many as 83 pieces of plastic in their guts.

The ingested plastic consisted primarily of fragments (94%), film (3%), fishing line (2%), and rope (woven filaments), Styrofoam and rubber (all <1%).

These plastics represented a wide variety of colours, with white, clear, and blue (87% total) being most prevalent. These colours are similar to those of plankton in the area, which a primary food source for these surface feeding fish (most of the species sampled are lanternfishes, which come to the surface at night to feed on plankton). This similarity in colour may explain why so much of this plastic is ingested by the fishes.

Although this study is the first to document the ingestion of plastic in oceanic fishes, the authors conclude that further study is needed to understand the impacts of plastic debris on the general health and life cycle of these fish, to investigate the potential for pollutant transfer to higher trophic levels, and to explore possible actions to protect aquatic life from plastic pollution.

In another similar study published in a more recent issue of the same journal, Brazilian scientists Fernanda Possetto and coauthors have shown that three species of marine catfishes (Cathorops spixii, C. agassizii and Sciades herzbergii) living in the Goiana estuary in northeastern Brazil also ingest a considerable amount of plastic debris.  

After analysing 182 individuals of the three species, the authors found that 18–33% of the individuals of each species had plastic items in their guts. In this case, the predominant plastic items were nylon fragments from fishing lines and nets.

For more information, see the paper: Boerger, CM, GL Lattin, SL Moore and CJ Moore (2010) Plastic ingestion by planktivorous fishes in the North Pacific Central Gyre. Marine Pollution Bulletin 60: 2275–2278.

Also see: Possatto, FE, M Barletta, MF Costa, JAI do Sul and DV Dantas (2011) Plastic debris ingestion by marine catfish: An unexpected fisheries impact Marine Pollution Bulletin doi:10.1016/j.marpolbul.2011.01.036