This story originally appeared on Yale Environment 360 and is part of the Climate office collaboration.
“Thousands of sea lampreys passed upstream [on the Connecticut River] every year. It is a predator that has wiped out the lake trout fishery in the Great Lakes. [Lampreys] literally suck the life out of their host fish, namely small fish like trout and salmon. Fish ladders should be used to reduce lamprey. Thus editorialized the Eagle-Tribune of Lawrence, Massachusetts, on December 15, 2002.
If that’s true, why this spring Trout Unlimited, the nation’s leading trout and salmon advocate, is helping the town of Wilton, Connecticut, and an environmental group called Save the Sound in a project that will restore 10 miles of habitat of sea lamprey spawning on the Norwalk River, which empties into Long Island Sound?
Why this summer will the first large returns of stocked Pacific lampreys – a species similar to sea lampreys – climb specially designed lamprey ramps at the Columbia River dams and invade Oregon’s historic spawning habitat, of Washington and Idaho?
And why, when the Turners Falls Canal on the Connecticut River is lowered in September, do the Connecticut River Conservancy, the Fort River Watershed Association, and the Biocitizen Environmental School rescue stranded sea lamprey larvae?
The answer is ecological awakening – the gradual realization that while all of nature is good, no part can be bad. In their natural habitat, sea lampreys are “keystone species” that support vast aquatic and terrestrial ecosystems. They provide food for insects, crayfish, fish, turtles, mink, otters, vultures, herons, loons, ospreys, eagles and hundreds of other predators and scavengers. Lamprey larvae, embedded in the stream bed, maintain water quality by feeding through filtration; and they attract breeding adults from the sea by releasing pheromones. Because the adults die after spawning, they infuse the barren headwaters with nutrients from the sea. When sea lampreys build their communal nests, they remove silt from the river bottom, providing spawning habitat for countless native fish, especially trout and salmon.
Environmental consultant Stephen Gephard, Connecticut’s former head of anadromous fish, calls lampreys “environmental engineers” as important to native ecosystems as beavers.
Sea lampreys, some 340 million years older than us, depend on cold, free-flowing fresh water to spawn. They are boneless, jawless, eel-like fish with fleshy fins. They extract bodily fluids from other fish via toothed suction discs. Sea lampreys and Pacific lampreys are widely reviled because they are perceived as “ugly” and because sea lampreys decimated native fish in the upper Great Lakes when they gained access to these waters via constructed channels man-made, most likely the Welland Canal which bypassed Niagara Falls. Once there, they nearly wiped out the valuable commercial and sport fisheries for lake trout (the largest species of Arctic char, not true trout like rainbows, cutthroats, and browns).
By the 1960s, non-native sea lampreys had reduced the annual commercial catch of lake trout in the upper Great Lakes from about 15 million pounds to half a million pounds. In 1955, Canada and the United States established the Great Lakes Fishery Commission, which controls lampreys with barriers, traps, and a remarkably selective larval poison called TFM. Lamprey control costs $15-20 million per year; and without it, the continued recovery of lake trout would be impossible and the populations of all other sport fish would plummet.
