Tuesday, December 31, 2013
We know that plastic washes up on our beaches, that turtles eat it and that seabirds die with bellies full of it—but it’s also in the fish we eat.
New research indicates that fish, directly or indirectly, eat bits of plastic, and lots of it. And not just the stuff on the surface but also plastics that drift at depth in the water column.
University of Hawai`i Department of Oceanography researchers Anela Choy and Jeffrey Drazen looked into the stomach contents of hundreds of fish from 10 deep ocean species. One in five had plastic in them. The accompanying image, from the University of Hawai`I at Manoa, shows some of the plastics removed from fishes.
We’re eating these fish, and we don’t fully understand what the impacts of the plastics may have on the fish, or on us,” the authors wrote.
“These observations are the first of their kind in scope and number, and suggest that more attention should be given to marine debris in subsurface waters as well as to poorly understood organismal and food web implications,” they wrote.
Their work, under the title, “Plastic for dinner? Observations of frequent plastic ingestion by pelagic predatory fishes from the central North Pacific,” was published in the journal Marine Ecology Progress Series.
The paper is available here.
You can find a University of Hawaii press release (less technical) about it here.
The researchers had NOAA fishery observers collect the stomachs of the catch from longline fisheries around Hawai`i. They collected samples from mahimahi, two kinds of opah, broadbill swordfish, longnose lancetfish, hauliuli or snake mackerel, walu or Hawaiian butterfish, and skipjack, yellowfin and bigeye tuna.
We tend to be aware of plastics floating on the surface, but this study found plastic in fish that only feed deep in the water column, suggesting that plastic pollution pervades the ocean at multiple levels.
They found that many of the plastics in the fish are not surface floaters, but have a density that allows them to drift at different depths.
The fish may not be eating the plastics directly—but rather already inside smaller creatures. The studied fish are, after all, predators. So, some fish may actually be mistaking plastics for food, but many may simply be feeding on plankton, small fishes, squids or crustaceans that have themselves eaten plastic.
It is all worrisome, the authors say: “Plastic ingestion in large pelagic fishes is more prevalent than previously suggested.”
“Many plastics adsorb PCBs, organochlorine pesticides, polycyclic aromatic hydrocarbons, metals, and petroleum hydrocarbons, some of which may desorb in acidic stomachs resulting in uptake to the animal. Indeed, it has been shown that seabirds that ingested plastic had higher PCB concentrations in their fat tissues, and seabird chicks fed plastics showed increasing PCB concentrations.
“Given the global commercial importance of … large pelagic fishes … future research might
evaluate whether these fishes carry elevated chemical toxin burdens that may ultimately pose a risk to the seafood-consuming public,” the authors wrote.
© Jan TenBruggencate 2013