U.S. Fish and Wildlife Service battles sea lampreys
Unfortunately, it belongs in its natural habitat, which basically is the Atlantic Ocean, not the Great Lakes and their tributaries where it has been causing fish mortality problems throughout the years.
U.S. Fish and Wildlife Service fisheries biologist Lynn Kanieski and biological service technician Chad Andresen talked about the invasive sea lamprey and efforts to control it Wednesday at the “Fishing After Hours” program put on by the Fred Waara Chapter of Trout Unlimited at the Landmark Inn.
“The lamprey species are one of the most ancient freshwater families in the world,” Kanieski said.
According to sealamprey.org, sea lampreys have remained largely unchanged for more than 340 million years, having survived at least four major extinction events.
What many people might not know is that the Great Lakes has native lampreys, which include the parasitic chestnut and silver lampreys and the non-parasitic northern brook and American brook lampreys.
“They also feed on fish,” Kanieski said. “They just don’t do the damage that the sea lampreys do.”
Once they attach to a fish, they start to feed on the body, fluids and blood, which eventually kills the fish, she said.
The sea lamprey entered the Great Lakes through the Welland Canal in the 1800s, which was built so ships could bypass Niagara Falls. Lampreys then slowly invaded the Great Lakes, making it all the way to Lake Superior in the 1930s, she said, with lampreys beginning to be counted by the 1950s.
The lampreys had a devastating effect on the fisheries. According to the Great Lakes Fishery Commission, before the sea lamprey invasion, the United States and Canada harvested about 15 million pounds of lake trout in the upper Great Lakes each year.
By the late 1940s, sea lamprey populations had exploded, feeding on important species like lake trout, lake whitefish and ciscoes. By the early 1960s, the catch had dropped to approximately 300,000 pounds — only about 2 percent of the previous average.
Lampreys have complicated life cycles, with one female capable of laying up to 60,000 eggs, although only a small number of those eggs hatch into larvae, Kanieski said.
“You get a lot of adults in, you get a big population of lamprey,” Kanieski said. “These lamprey will run up all the way to the headwaters in some streams if there’s great spawning habitat.”
In the larval stage, they typically live in stream sediment three to six years. When they reach 5 inches, the lampreys develop their eyes, sucker mouths and teeth. Once they get to that stage in the fall, they start to head out out of the stream and into the Great Lakes, she said.
Then the lampreys start feeding on fish, beginning with smaller fishes and then moving on to larger prey — but not other lampreys.
“I’ve never heard of any documentation of them actually parasitizing each other,” Andresen said.
He also pointed out lampreys prefer small-scaled fish because it can be easier for them to “rasp through” those species.
Kanieski noted they’re in the parasitic stage for only 18 months, spending most of their time in the lower part of the water column.
“They’re pretty adaptable animals,” Kanieski said. “Originally, they came from the ocean, and now these have adapted to the freshwater Great Lakes.”
Once they return to the streams to spawn, though, they are no longer feeding.
Kanieski said that some of the earliest control methods in the 1950s included screen barriers, but they were labor-intensive and vulnerable to washouts. Later that decade, electrical barriers began to be installed, although they were susceptible to power outages and flooding.
Research then began to create a chemical lampricide: 3-Trifluoromethyl-4-nitrophenol, or TFM. Being primitive fish, lampreys don’t have the enzymes to break down the chemicals, she said.
Lake Superior then was treated, and combined with the stocking of lake trout, numbers of desirable fish began to increase.
However, wildlife professionals have to be vigilant with continuous lamprey management.
Kanieski said sea lampreys have been observed in 536 Great Lakes tributaries, and on average, 200 to 250 streams are treated every three to five years on a cycle.
“A lot of these will include large and high-quality streams across the Great Lakes,” said Kanieski, who noted assessment surveys conducted to determine presence, abundance and distribution of sea lamprey larvae in these streams help biologists determine which streams need to be treated with TFM.
She acknowledged that TFM does affect the native lampreys, which is one of the downsides of the management program. That fact also is considered before the USFWS treats spots; if a stream has a relatively small number of sea lampreys, it will be monitored as opposed to wiping out a large native population.
One of the USFWS’s objectives in its sea lamprey management program is to reduce the use of lampricide without reducing the level of lamprey control, which Kanieski said is a challenge.
Other control methods now in use include barriers, traps and sterile male release. Methods in the field-testing stages involve using lamprey pheromones as trap bait, a low-voltage direct-current system to guide lampreys into traps and alarm cues that could block them from certain areas, or in conjunction with pheromones, work in a push-pull technique.
The overall management program already has shown good results. Kanieski said Lake Huron has shown a 30-year low in lamprey numbers, with Lake Michigan showing a 20-year low. Lake Superior is on a downward trend, as is the case with Lake Ontario, but the abundance still is high in Lake Erie.
However, she said efforts can’t be relaxed, even though sea lampreys won’t be eradicated.
And even leaving just one large stream untreated will have severe consequences.
“Any reduction in control will result in an unacceptable increase in sea lamprey damage,” Kanieski said.
Christie Bleck can be reached at 906-228-2500, ext. 250. Her email address is firstname.lastname@example.org.