TRAVERSE CITY (AP) – Populations of invasive, fish-killing sea lampreys have fallen to their lowest point in decades across the Great Lakes, showing that control measures costing millions of dollars a year are paying off, officials said Wednesday.
Lamprey numbers have reached a 30-year low in Lake Huron and a 20-year low in Lake Michigan, according to the Great Lakes Fishery Commission, a U.S.-Canadian organization. Numbers also are down significantly in the other lakes.
“Sea lamprey control is worth the effort and is the foundation of the fishery we enjoy today,” said Robert Hecky, chairman of the commission. “Before control, sea lampreys caused major economic and ecological harm. Today, fish communities are on the rebound and the fishery is worth $7 billion annually to the people of Canada and the United States.”
The lamprey is an eel-like creature that uses its suction-cup mouth and sharp teeth to fasten itself to other fish and suck out their bodily fluids. The average lamprey kills up to 40 pounds of fish in its lifetime.
The invader made its way from the Atlantic Ocean to the Great Lakes through shipping canals and had spread across the freshwater seas by the late 1930s. The infestation was especially devastating to prized native species such as trout and whitefish, although lampreys also feast on smaller fish such as walleye and perch.
A turning point was the development of a poison that kills lampreys in their larval stage, as they develop in rivers before migrating to the lakes as adults. Barriers and traps also have been effective. The commission is experimenting with sex pheromones that would lure lampreys away from spawning areas.
Lampreys killed about 103 million pounds of fish per year in the lakes before control measures began, Hecky said. Now, the annual toll is below 10 million pounds.
Lake Huron’s lamprey population, once the largest in the Great Lakes, has dropped from 440,000 in the early 1990s to about 69,000 – an 85 percent decline, commission spokesman Marc Gaden said. The population is estimated at 80,000 in Lake Superior, 27,000 in Lake Michigan, 24,000 in Lake Ontario and 10,000 in Lake Erie.
Although falling, lamprey numbers are still high enough in Lakes Erie and Superior to pose a significant risk to other fish species, Gaden said.
Control measures must continue indefinitely because it’s virtually impossible to get rid of all lampreys and even a temporary letup would allow them to rebound, he said. The U.S. spends about $14 million a year on lamprey control, while Canada spends about $7 million.
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