Fish eat plastic -- and they like it, too

New research has found that the 'scent' of plastic in seawater appeals to foraging fish.

Fish eat plastic. We know this because scientists have detected significant amounts of plastic in the seafood that ends up on dinner plates. Research from the University of Ghent last year said that the average mussel-eating Belgian ingests 11,000 pieces of microplastic annually, while other research detected synthetic clothing fibers in one-quarter of fish at the San Francisco fish market.

This is concerning for a lot of reasons, not least of which is the passing on of toxic compounds in plastic to human eaters through bio-accumulation in fish tissues, as well as the impact on fish behavior, from reduced activity rates to weakened schooling behavior to compromised liver function.

The big question, though, is why are fish mistaking plastic for food? Surely these substances are different enough that a fish would be able to tell the difference?

Apparently not.

As Matthew Savoca explains in a piece for the Washington Post, fish may actually like the smell of plastic in the water. Savoca was part of a research team that conducted experiments on anchovy schools and published the results last month in Proceedings of the Royal Society.

Anchovies are a forage fish commonly found off the western coast of North America. They are a key part of the food chain, providing important sustenance to larger predators. They are known to eat plastic, but before this experiment, scientists did not know if anchovies (like sharks) used a sense of smell to detect their food.

It turns out, they do. Savoca’s team worked with anchovy schools at San Francisco’s Aquarium of the Bay, using a GoPro camera mounted above a tank. The researchers mixed up two different solutions of water – one steeped in krill, anchovies’ preferred food, and anther steeped in plastic debris. These solutions were introduced at separate times into the tank and the anchovies’ behavior was observed. Savoca wrote:

“When we injected seawater scented with krill into the tank, the anchovies responded as if they were searching for food — which in this case was not there. When we presented them with seawater scented with odors of plastic debris, the schools responded in nearly the same way, clumping together and moving erratically as they would if they were searching for food. This reaction provided the first behavioral evidence that a marine vertebrate may be tricked into consuming plastic because of the way it smells.”

This research has confirmed that anchovies use a sense of smell to detect their food, and that they are confused, even attracted, by the scent released by plastic in the water. This is a serious problem, when you consider the sheer volume of plastic waste being discharged into the world’s oceans on a daily basis – the equivalent of a dump truck load per minute.

plastic-filled fishErik Forsberg -- Sadly, public art installations such as this plastic-filled fish are disturbingly accurate depictions of reality./CC BY 2.0

The need to move away from single-use plastics is more pressing than ever, and hopefully research such as this will help motivate people to change their habits, replacing disposable items and packaging with reusable ones.

Tags: Animals | Animal Welfare | Fish | Oceans | Plastics | Pollution

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