Looking for plastic-free fish? Here's one to put on the menu

There's growing concern about the amount of plastic ending up in the world's oceans, but researchers have found a fish that doesn't seem to consume it at all.

Nearly half of fish species studied may not be ingesting harmful plastics

A researcher prepares to look for plastics in the GI tract of a cod caught in Newfoundland waters. (CLEAR)

There's growing concern about the amount of plastic ending up in the world's oceans, but researchers at Memorial University of Newfoundland have found one fish that doesn't seem to consume it at all.

And they say despite the doom and gloom news reports, 41 per cent of all fish species studied in published research don't appear to ingest plastics either.

Max Liboiron, an assistant professor of geography and a specialist in environmental pollution at MUN, examined the gastrointestinal contents of 134 silver hake caught in 2014 and 2015 on the Grand Banks.

"They were eating in places that do have plastics in them all off the south shore of Newfoundland, and none of them ate plastic, so they're not a species that eat plastic," Liboiron told CBC Radio's Central Morning Show.

Silver hake (Merluccius bilinearis) are bottom dwellers found in the warmer waters of the Atlantic. The whitefish is often used to make imitation crab. (Fisheries and Oceans Canada)

Liboiron is interested in determining how much plastic fish consume because the material can absorb oily chemicals such as pesticides and methylmercury, which are then absorbed by the fish, which are in turn eaten by other animals and humans.

The endocrine system-disrupting chemicals that leach from plastics have been linked to a number of human health problems, such as cancer, developmental delays, obesity and thyroid problems.

Salmon and capelin found plastic free

Liboiron has also studied salmon and capelin caught in Newfoundland and Labrador waters, and found they weren't consuming plastics either. But the results were very specific to a certain life stage of those fish.

"When we catch capelin and salmon in this province they are usually spawning, and a lot of fish don't eat when they're spawning, so we don't know if they don't eat plastic all the time, or just at the end of their spawning careers," said Liboiron.

"Silver hake are unique because they were eating, and they still didn't eat plastic."

Surprising finding is 'super normal'

The researchers thought they were on to something when they found no plastic in the guts of the silver hake, but it turns out that the fish might not be unique after all.

"When we first found the results we were shocked. We were like, 'Oh my god, it's the only fish in the world.'"

However, when they looked at 211 other studies on fish ingestion of plastics, they found the silver hake was not alone.

Max Liboiron studies ocean plastics at Memorial University. (Ted Dillon/CBC)
 

"We also found it was amazing, and exceptional, and weird, so we actually looked at a whole bunch of studies on fish ingestion of plastics and found that 41 per cent of all species ever studied don't eat plastic, so it's actually super normal."

Liboiron said the doom and gloom results from scientific studies tend to get published, but when researchers find nothing alarming it doesn't usually get much attention.

"The problem is most scientists are pressed to publish more fancy, exciting, charismatic, dreadful sort of results, so these zero per cents were hidden in the results because they would look at four or five or 20 species and then publish the overall ingestion rate, so fish that eat zero would just sort of get lost in that numerically," explained Liboiron.

"So it turns out almost half of all fish might not be eating plastics."

Cod caught off Newfoundland were found to have a low plastic ingestion rate. (CBC)

However, Liboiron said in 66 per cent of the studies the sample sizes were too low to be conclusive.

According to Liboiron, the plastic ingestion rate for many fish off Newfoundland is low.

In cod, the rate was two per cent, meaning only two out of every 100 cod were found to have consumed plastic.

She said tropical fish that feed on the water's surface, such as the southern mullet, tend to have the highest plastic ingestion rates.

With files from Central Morning