[OANNES Foro] Plastic in the ocean smells like junk food to hungry anchovies

[Mario Cabrejos]

Plastic in the ocean smells like junk food to hungry anchovies

by  <https://news.mongabay.com/by/vicky-stein/> Vicky Stein

29 November 2017

https://news.mongabay.com/2017/11/plastic-in-the-ocean-smells-like-junk-food
-to-hungry-anchovies/

As plastic debris drifts through the ocean, it accumulates a coating of
algae and bacteria. That coating smells delectable - that is, if you're a
fish.

Northern anchovies (Engraulis mordax) find the scent of "biofouled" plastic
irresistible, according to a recent study published in the Proceedings of
the Royal Society B. The silvery schooling fish detect the scent that marine
algae and bacteria transfer onto bits of plastic, and launch into a
flashing, darting feeding frenzy.

Anchovies are an ecologically and economically important species of baitfish
in temperate waters worldwide. In the northern Pacific Ocean, they are food
for whales, tuna and humans, among many other species. But if anchovies fill
up with plastic, their consumers may have to contend with a new kind of junk
in their food.

The paper's lead author, Matthew Savoca, is a fellow at the U.S. National
Oceanic and Atmospheric Administration in Monterey, California, researching
the effects of pollution and litter on the ocean and its resources. His
study is one of the first to demonstrate the importance of scent to fish
like anchovies. And it reveals one reason that marine animals might be drawn
to plastic in the first place.

"People try to make hypotheses about the color, shape and size of plastic
pieces, but to me this [odor] hypothesis seems like one that was really
important to test," said ecologist Chelsea Rochman, an assistant professor
at the University of Toronto, who was not involved in this study.

To determine if anchovies responded to plastics by smell, Savoca and his
team created a strange collection of marine teas. They created different
scented liquids by steeping biofouled plastic, clean plastic and krill. They
released their brews, along with control samples of clean water, into
schools of hundreds of anchovies, set up in tanks at the Aquarium of the Bay
in San Francisco.

When the anchovies smelled either their favorite food - small swarming
crustaceans called krill - or Savoca's smelly plastic tea, they responded
dramatically. "They darted and dashed in various directions, which is
indicative of the foraging behavior of these animals," Savoca said in an
interview. "These fish are just going bananas for the food and the plastic,
really."

But when the fish smelled the clean plastic and plain water, they just kept
swimming in their usual circles.

Savoca realized this behavior might historically have been helpful to the
fish. "When animals eat plastic, they're not actually making a dumb
decision," he pointed out. "It might smell like food, look like food, taste
like food. It will be really hard for them to learn to reject this stuff as
'not food.'"

 <http://science.sciencemag.org/content/347/6223/768> One estimate from a
2015 study suggested that the rate of plastic entering the oceans worldwide
in 2010 was roughly one dump truck load per minute. That added an estimated
8 million metric tons of plastic to the ocean that year alone. Despite some
efforts, plastic production and pollution isn't slowing down.

Savoca and other researchers are starting to examine the effects on fish
fooled into eating biofouled plastic - and the possible consequences for
their predators, such as whales.

Billions of people worldwide rely on seafood as their main protein source,
Rochman noted, and their diet may be getting riskier. Plastics contain
myriad harmful chemicals (with acronyms such as BPA and DEHP) that
potentially move more easily into the bodies of fish through a coating of
algae and bacteria. Humans, said Rochman, could start to find evidence of
plastic-polluted water in their fillets and fish sticks.

"We have to act now when we're seeing relatively small amounts of plastic in
the animals we're eating," said Savoca. "This could become a problem of
human health concerns and not just animal health concerns."

CITATION

*	Savoca MS, Tyson CW, McGill M, Slager CJ. (2017) Odours from marine
plastic debris induce food search behaviours in a forage fish. Proceedings
of the Royal Society B 284: 20171000. doi: 10.1098/rspb.2017.1000

 



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