Biologist studies fish lures Ingestion of plastic, rubber focus of tests

UNITY – A marine biologist with the Maine Department of Inland Fisheries and Wildlife hopes that his study will help to determine the effects of plastic and rubber lures on fish that swallow them.

Scuba divers and fisheries biologists have found these lures, made in a variety of shapes, sizes and colors, littering the bottoms of Maine’s lakes and ponds as bass fishing grows in popularity.

But Russell Danner is more interested in what happens to them when they’re ingested by fish.

“We’re just looking to see if it causes any health problems,” Danner said.

Danner’s study could lead to legislation that would curtail the use of traditional, indigestible plastic lures. Since biodegradable artificial lures are already on the market, “they would be a good choice even now,” he said.

To study the lures’ effects, Danner split 70 hatchery-raised brook trout into two groups, placing them in tanks at Unity College. Over 90 days, one group of fish was fed food, while the second group ate food spiked with soft plastic lures.

The feeding portion of the study ended last week, when the fish were euthanized and Danner began a battery of tests.

He was startled to find that fish were eating large pieces of lures that were remaining undigested in their stomachs.

Slicing open a 9-inch trout in the laboratory, Danner discovered a 1-inch-long piece of rubber worm in its belly. Later, a 9-inch plastic salamander popped out when Danner cut into a similar-size fish.

Because the fish were fed different-colored lures each week, Danner will be able to learn how long the lures stay with the fish.

Jim Chacko, the college’s professor of aquaculture, discovered a difference even before the fish were euthanized. Holding a small can of food, he tossed a small handful into the tank with the healthy fish, which swarmed to the top to grab a piece.

When food was tossed into the tank of fish that had consumed the lures, however, the fish slowly made their way to the top to nibble.

“I think it’s because their stomach is full so their reaction is very slow,” Chacko said.

Danner found an excess amount of green bile inside a number of fish, an indication the fish are not eating properly, he said.

The fish were measured and weighed and a blood sample was taken to measure glucose levels, the ratio of red blood cells and blood protein.

The readings, measurements, stomach and liver contents, and the fish themselves, will be compared to those provided by the pure food group to learn how the plastic lures affect the fish’s overall health.