Serving Northern St. Louis County, Minnesota

PLASTICS IN THE ENVIRONMENT

Lure, litter, or worse?

Studies show there’s reason for concern over the use of soft plastic baits

Marshall Helmberger
Posted 7/17/19

REGIONAL — For decades, anglers have increasingly turned to soft, plastic fishing baits to lure everything from bass to lake trout here in the North Country. The popularity of these baits is …

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PLASTICS IN THE ENVIRONMENT

Lure, litter, or worse?

Studies show there’s reason for concern over the use of soft plastic baits

Posted

REGIONAL — For decades, anglers have increasingly turned to soft, plastic fishing baits to lure everything from bass to lake trout here in the North Country. The popularity of these baits is evident from any visit to an area tackle shop, where anglers will typically find a large and colorful line-up of different bait styles and brands.

There’s plenty of angler experience to demonstrate that these baits can be very effective in luring fish to bite. They’re soft, like live bait, and they’re typically infused with chemical scents that make them attractive to predator fish.

Yet, despite the widespread use of these baits, researchers have only started to ask questions about their potential impact on popular game fish. Even less is known about how these baits might be affecting aquatic ecosystems in general.

One thing that’s known for sure is that these plastic baits are showing up in the digestive systems of at least some fish right here in Minnesota, although not in significant numbers.

“It’s not really on our radar here,” said Edie Evarts, area fisheries supervisor in Tower. While Evarts said area fisheries staff do occasionally find soft plastic baits in the stomachs of fish they catch as part of their annual test netting, she said it’s only an occasional occurrence.

The few studies that have examined this issue have yielded varying results as to how often fish ingest soft plastic baits in the wild. Some studies have found just two or three percent of fish examined had such baits in their system, while other surveys have suggested the number could be as high as 25 percent.

“If there was a 20-30-percent occurrence here, we’d know about it,” said Evarts.

Eric Sanft, a fisheries biologist with the Minnesota Department of Natural Resources, has conducted some of the most recent research on the topic as part of his graduate studies in Illinois, and he concurs with Evarts that, at least for now, relatively few fish are ingesting these artificial baits in the wild. Still, he acknowledges, enough anglers are finding the material inside fish they clean to raise questions. “It can generate a lot of concern on [fishing] forums,” said Sanft.

Sanft’s 2018 study suggests that largemouth bass are able to regurgitate soft plastic baits, usually within a few days, suggesting that the impact on individual bass may be limited.

But a 2009 study of brook trout that were fed soft plastic baits under laboratory conditions showed they suffered significant ill effects as the baits blocked their digestive systems and prompted the fish to lose substantial amounts of weight even when in tanks with plentiful natural food.

The broader impact on lakes is less clear. Without question, the baits do accumulate on lake bottoms over time, as fish bite off portions and later regurgitate them into the water. Some anglers will also discard unused bait into the water, further adding to the plastic litter covering popular lake bottoms. A 2014 study of a popular fishing lake in eastern Ontario, estimated that anglers lost more than 12,000 soft plastic baits during the course of a year on the lake.

If those baits remained inert, it might mitigate some of the concern. However, researchers note that most soft plastic baits are manufactured from a combination of PVC and chemicals known as “plasticizers” which give the baits their rubbery feel. Those plasticizers typically contain other chemicals known as “phthalates,” which are known endocrine disruptors and which can leach from the PVC into lake water. “Phthalates can have toxic effects on freshwater fish including alteration in enzyme activity and mortality,” noted Sanft in his 2018 paper, citing a 2002 study. Sanft said he had hoped to study any possible effects on fish from ingestion of phthalates, but he said the bass he studied didn’t retain the baits in their systems long enough to leach any noticeable amount of the toxic chemicals.

To date, no states have banned the use of soft plastic baits, although the state of Maine has considered such a ban citing environmental concerns. However, a 2014 report by the Maine Department of Inland Fisheries and Wildlife recommended against a ban, in favor of educating anglers about the potential harm that such baits can cause and encouraging them to recycle or properly dispose of unused baits. The department also urged the Maine Legislature to encourage the industry to move to more natural products that truly biodegrade.

Some soft bait manufacturers already claim that their baits are biodegradable, but biologists have stressed that those claims have not been confirmed by research. While some types of plastic are advertised as biodegradable, it often means the plastic breaks down into much smaller pieces, which can then become incorporated in the environment with effects that remain largely unknown.

And researchers question how effectively biodegradable plastics break down in the natural environment. While such plastics can biodegrade in industrial composting facilities where high temperatures encourage the growth of the bacteria that feed on the material, such conditions are unlikely to be re-created in a natural environment, particularly in North Country lakes.

According to Evarts, if there’s one thing that is keeping demand for soft plastic baits in check in Minnesota, it’s the relative abundance of various natural bait. Anglers here still rely heavily on minnows, leeches, and nightcrawlers, and those baits generally remain plentiful enough to meet that demand.

Evarts notes, too, that many of the plastic baits are geared toward bass fishing, which comprises a relatively small slice of the angling activity here in walleye country. Still, the DNR doesn’t really know how many anglers are regularly using soft plastics. “We haven’t been tracking it,” said Evarts. “We don’t ask about bait in our creel surveys anymore.”

While Sanft doesn’t believe that soft plastic baits pose any major risk to most fish, he said anglers need to do their part to make sure they dispose of any unused bait properly. “You may not be killing fish, but it is litter and no one wants to see that in their lake. Just be responsible.”

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