Treating infestation of sea lamprey
ALPENA TOWNSHIP – The rain fell and a cloud of mosquitos descended on a United States Fish and Wildlife Service crew as they worked to rid Cranberry Creek of sea lampreys Thursday.
Over the course of 12 hours, the crew of six put a chemical in the creek to rid an infested stretch of sea lamprey larvae, treatment Supervisor Jenna Tews said. Their work is part of an international effort to eradicate the parasitic, invasive species. While Cranberry Creek may seem small, it’s capable of producing sizable numbers of lampreys, each one of which can destroy 40 pounds of fish in its lifetime.
“One thing I want to stress is that this is an ongoing battle,” she said. “Our work continues every year. Both the U.S. and Canada are working at treating the sea lamprey infestation in the Great Lakes.”
At one point, Tews collected a sample of some of the lamprey larvae killed by the chemical. Over the course of 20 minutes, she gathered about 50 to 75 larvae in one spot. Imagine how many might have been living in 1.2 miles of creek, she said. That’s the length of Cranberry Creek determined to be infested by a USFWS larval assessment crew which checked it a year prior.
“We work really hard on this thing,” she said. “The bugs are outrageous, it’s raining pretty hard and we’re on ATVs hauling chemicals back and forth to treat this stream,” she said.
Like many rivers and streams in the area, USFWS crews treat Cranberry Creek – also known as Squaw Creek – on a rotating basis, Tews said. It’s the third time the creek has been treated since the 1960s, with the most recent being in 2008. Her crew is part of a larger one currently working in Alpena and Cheboygan counties, and hers will be treating Long Lake Creek between Devils Lake and Lake Huron on Saturday.
The crew set up an automated pump near an off-road vehicle trail to put lampricide into the creek’s infested area, Biological Science Technician Gena Long said. The pump feeds in a measured amount of the chemical at a constant rate. Long then went a ways downstream and measured the concentration of the chemical, while Gena Long, another technician, verified the pump’s output rate. Crew members performed this check every half-hour throughout the day.
By factoring in the stream’s rate of flow, alkalinity and acidity, technicians can determine the ideal concentration to ensure the treatment is effective, Tews said. An automated sampler checked the stream near US-23, not far from where it empties into Lake Huron. Technicians can check its results to see if the lampricide concentration was high enough at the other end of the treated area.
“We’ll usually work a day or two gathering preliminary information on a stream,” she said.
Lampricide kills the lampreys before they become juveniles and start feeding on fish blood and bodily fluids in Lake Huron, Tews said. As larvae, they stay burrowed in creek or river beds where the spawning adults left them.
Despite the hard work, sour weather and bloodthirsty insects, Tews believes the work is worth it, she said. Each female lamprey she and her crew killed that day could’ve gone on to lay hundreds of thousands of eggs at a time, spawning more fish-killing lampreys.
“If you can treat one mile of a stream, that’s one tiny little notch we’ve taken care of,” she said.