DULUTH, Minn. _ Val Brady and Donn Branstrator, University of Minnesota Duluth scientists, were at a boat landing on Island Lake north of Duluth when one of Brady's neighbors happened to show up to go fishing.
The conversation moved to what the scientists were doing that day, research on how invasive spiny water fleas can accumulate on anglers' fishing gear, when the neighbor weighed in with his opinion.
Why bother, he said, everyone knows spiny water fleas are spread by ducks.
Uff da!
There's little evidence that birds play any major role in the movement of spiny water fleas. Waterfowl are usually near the surface and near shore, while spinys are down deep and in the middle of the lake. It's also unlikely spinys could survive the gut of a bird.
But multiple studies have shown that humans unintentionally moving invasive species from lake to lake is a major factor in their spread _ that the presence of public boat landings is the biggest factor in whether a lake is infested.
And now new research from Brady and Branstrator has found that fishing line may be one of the most likely way that spiny water fleas can hitchhike on our gear.
In the first major study of its kind, the researchers tested monofilament, fluorocarbon and braided fishing line as well as anchor ropes, bait buckets, downrigger cables and livewells to see which were the most likely to pick up and hold spiny water fleas. All of them held some amount of spiny water fleas, but one stood out with the most.
"It's fishing line, by far," Bantstrator noted of the findings. There seemed to be little difference in the type of fishing line, he said, spinys could ride along on all of them.
Researchers trolled fishing line, deployed anchor ropes and towed bait buckets through Mille Lacs Lake and Island Lake Reservoir near Duluth _ 36 different sessions in each lake _ and found the same results. Half the sessions were in daylight, when spinys are down deeper, and half at night when they often rise toward the surface.
"I really expected anchor ropes to be the worst offenders, but they weren't even close" to fishing line, Brady noted.
The difference may be because anchor ropes are usually stationary, while fishing line covers more water with more opportunity to snag spinys down deeper. Bait buckets are towed alongside boats on the surface and water flows through them, making them less able to hold spinys. Livewells, too, touch only surface water.
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