Plastic is rapidly becoming a significant "food" item for fishes living in the northern Pacific Ocean, according to a study published in a recent issue of the journal Marine Ecology Progress Series.
Peter Davison and Rebecca Asch of the Scripps Institution of Oceanography revealed that 9.2% of the mesopelagic fishes they sampled in the North Pacific Subtropical Gyre (NPSG) contained plastic waste in their guts.
The NPSG (also known as the North Pacific Central Gyre or North Pacific Gyre) is a convergence zone delineated by four prevailing ocean currents. Because of the very mild currents within the gyre, it is home to an extensive field of marine debris (primarily comprising plastic trash) suspended in the water that has been popularly called the Great Pacific Garbage Patch.
The results were part of the SEAPLEX (Scripps Environmental Accumulation of Plastic Expedition) expedition conducted in August 2009, in which fish specimens, water samples and marine debris were collected over 2375 kilometres of the NPSG at various depths.
A total of 141 fish specimens collected, representing 27 species in four families, were dissected, and 13 specimens were found to have plastic waste in their guts. The plastic waste that the fishes ingested were typically plastic debris broken down into pieces smaller than a human fingernail.
The results approximate those of earlier studies which point to an increasing prevalence of plastic debris being ingested by fishes (particularly plankton-feeding species).
Based on their results, the authors estimate that 12,000-24,000 tons of plastic are ingested by the mesopelagic fishes of the NPSG annually.
Similar rates of plastic ingestion by fishes are thought to occur in other subtropical gyres, where the convergence of currents leads to the accumulation of plastic debris.
For more information, see the paper: Davison, P and RG Asch (2011) Plastic ingestion by mesopelagic fishes in the North Pacific Subtropical Gyre. Marine Ecology Progress Series 432, pp. 173–180.
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