How, and how much, are soft plastics affecting fish?

The lake trout fishing was good on a recent trip in Ontario’s Quetico Provincial Park, just north of Minnesota’s Boundary Waters Canoe Area Wilderness.

The four of us, trolling minnow-imitation crankbaits behind canoes in early May, had caught plenty of fish. A couple of us were filleting three fish for supper. That’s when we discovered something that made each of us a little uncomfortable.

One of the lake trout, not more than a 3-pounder, had two soft plastic minnows and a 7-inch plastic worm in its stomach. Because the ice had gone out just a few days before and because we had seen no other anglers, we assumed that the fish likely had been swimming around with those plastic baits in its stomach since at least last summer.

Pretty discouraging.

We use soft plastics only occasionally for lake trout fishing, but soft plastics are commonly used by bass anglers across the country. Similar plastics are used by walleye anglers who fish Quetico Provincial Park, where no organic bait of any kind is permitted.

Fish can ingest plastics not only if they’re discarded but if a fish pulls a plastic bait off an angler’s hook when striking.

Although the lake trout we were cleaning looked healthy, those three baits had been taking up a lot of room in its stomach. We wondered how the fish had continued to eat and whether it had continued to grow. Maybe it should have been a 5-pounder.

A bit of searching will get you to a lot of internet discussion about the use of soft plastics in fishing. A study conducted at Unity College in Maine, reported in the Bangor Daily News, found that 65 percent of brook trout voluntarily consumed soft plastic lures if they were dropped into the water. Researchers reported that fish retained the lures in their stomachs for at least 13 weeks without regurgitating them. The fish also began to act anorexic and lost weight within 90 days of eating a soft plastic lure, according to researchers.

The scientists who conducted the study strongly encouraged anglers to purchase biodegradable and food-based lures rather than soft plastics, the newspaper reported.

Elsewhere online, columns written by professional bass anglers indicate that tossing used or damaged soft plastic baits overboard is common among bass anglers, although some bass pros are trying to persuade others to stop the practice.

Just how many fish are ingesting soft plastic lures remains unclear, according to a January 2016 paper by Jordan Skaggs and Micheal S. Allen, described in an American Fisheries Society publication.

According to a creel survey, 25 of 42 anglers (60 percent) who harvested lake trout on Charleston Lake, Ontario, reported finding soft plastics in the fishes’ stomachs. However, stomach content analysis of fish from gill-net sampling and hook-and-line angling revealed that only 2.2 percent of lake trout stomachs and 3.4 percent of smallmouth bass stomachs contained soft plastics.

It appears much remains to be known about how soft plastics are affecting fish populations.

“It is uncertain whether SPLs (soft plastic lures) cause individual or population-level effects upon fish growth and survival,” Skaggs and Allen wrote.

Common sense would tell an angler that plastics aren’t good for fish and we should all think about how we use and dispose of them.