Notorious anniversary: 100 years of the sea lamprey in the Great Lakes
The parasitic invaders decimated the fish populations of the Great Lakes.
Sea lampreys have been kept under control since the Great Lakes Fishery Commission began control efforts in the United States and Canada. Their numbers have decreased by 90% in the Great Lakes, but only with ongoing chemical applications and an annual investment of $ 25 million.
The crews distribute a certain chemical poison in 120 tributaries in the area, which switch between streams every three or four years to kill the lamprey larvae before they grow large and go into the lakes to feed on fish. Adult lamprey swim in the lake until they find a host fish to attach to, then they suck the life blood from the fish and eventually cripple and kill it.
Of the dozen invasive species that have invaded the Great Lakes in the past 100 years, none have done anywhere near the damage like sea lamprey. But none was included that well either.
The mouth of a sea lamprey. In November, it will be 100 years since the first invading lamprey was found in the Great Lakes. Post / Minnesota Sea Grant
Today, sport and commercial fishing in the Great Lakes “is valued at $ 7 billion annually, so the cost of controlling the sea lamprey is expensive but is only a small fraction of the value of the fishery,” Marc Gaden, Communications director for the Great Lakes Fishery Commission told the News Tribune.
If efforts were stopped, the lamprey numbers would quickly recover and the fish stocks in the lake would again decimate within a few years, Gaden noted.
In addition to chemical control, the commission was involved in building 75 barriers to stop lampreys spawning, similar to the one on the Bois Brule River in Wisconsin since 1984. As long as the dams can be modified to allow fish to pass upriver, barriers will work good to stop lamprey. In addition, rivers with working barriers don’t need chemical treatments, Gaden noted.
The Great Lakes Fishery Commission was founded in 1954 by an international convention between the USA and Canada to specifically counteract the decline in fish populations. But even before that, as early as 1946, scientists were concerned with the use of chemicals to combat lampreys. More than 6,000 chemicals were tested when they finally found in 1956 that 3-trifluoromethyl-4-nitrophenol (TFM) killed lamprey larvae but did not harm rainbow trout and blue gills swimming in the same test tube.
After several field tests to confirm the laboratory results, TFM was first used in May 1958 in what is now Elliot Creek, a tributary of Lake Huron. In 1963, a second compound, 5,2-dichloro-4-nitrosalicylanilide (niclosamide), was also found to be selectively toxic to sea lamprey larvae. The two chemical lampricides are the backbone of the sea lamprey control program to this day.
“It’s easy to forget how disastrous the viability and productivity of fishing in the Great Lakes became after the invasion of Lake Erie and Upper Lakes,” said William Taylor, Michigan State University professor and chairman of the Great Lakes Fishery Commission, in a statement.
Other attempts to control lampreys by deceiving their sense of smell and luring them into traps are also being explored.
A long bath inland
Sea lamprey are native to the Atlantic Ocean. They first invaded the Finger Lakes of New York and Lake Ontario in the mid-19th century through man-made canals. Fishermen back then observed the damage sea lampreys were doing in this region, but it was believed that Niagara Falls would prevent them from entering the Great Lakes. This was true until a major renovation of the Welland Canal, the man-made link between Lakes Ontario and Erie, which allowed the sea lamprey to bypass the falls.
On November 8, 1921, Ontario fisherman Alexander Crewe was pulling nets full of whitefish from central Lake Erie when he noticed a lamprey that was much larger than the native species he was used to. He sent the specimen to the University of Toronto, which confirmed it was a sea lamprey.
It took another 18 years for the lamprey to reach Lake Superior and start killing lake trout here, but the invaders had a quick impact after that. In the early 1940s, even after decades of intensive net fishing, commercial fishermen caught nearly 400,000 pounds of lake trout annually from the waters of Lake Superior in Minnesota. By the early 1960s this had dropped to almost zero. The state closed the lake entirely to nets in 1962.
Treatment of lampricide in Lake Superior streams began in 1958, but it wasn’t until the 1970s that lake trout stocks began to recover. After some ups and downs, the large lake now has strong sport fishing for trout and commercial fishing in some areas. Lake trout have recovered so well in the waters of the Minnesota lake that the state Department of Natural Resources says stocking is no longer required.
A US Fish and Wildlife Service fish biologist uses electric paddles to collect lamprey larvae in the Nemadji River in Carlton County. The Nemadji is one of 120 tributaries of the Great Lakes that are regularly treated with a chemical that kills sea lamprey larvae but does not harm most other species. Clint Austin / 2004 Files / Duluth News Tribune
It’s not that lampreys have been eliminated. Their pre-control numbers were estimated at 780,000 adult lampreys in Lake Superior in the 1950s. That is reduced by 76% today to an estimated 184,000 lampreys in the lake. The Great Lakes Fishery Commission hopes to reduce that number to about 48,000. Lamprey numbers are down 93% in Lake Michigan and Ontario, 84% in Lake Huron, and 50% in Lake Erie.
“Today the control of sea lamprey in the Great Lakes is remarkably successful,” said commission vice chairman James McKane of Kitchener, Ontario. âOver the past six and a half decades, the Great Lakes Fishery Commission and its partners have reduced sea lamprey populations in most areas by 90%. … Without the control of sea lamprey, the $ 7 billion fishery would cease to exist. ”
John Myers reports on nature, the environment and natural resources for the Duluth News Tribune. He can be reached at firstname.lastname@example.org.