This story initially appeared on Yale Environment 360 and is a part of the Climate Desk collaboration.

“Thousands of sea lamprey are passed upstream [on the Connecticut River] each year. This is a predator that wiped out the Great Lakes lake-trout fishery. [Lampreys] literally suck the life out of their host fish, namely small-scale fish such as trout and salmon. The fish ladders ought to be used to diminish the lamprey.” So editorialized the Eagle-Tribune of Lawrence, Massachusetts, on December 15, 2002.

If that’s true, why this spring is Trout Unlimited—the nation’s main advocate for trout and salmon—helping the Town of Wilton, Connecticut, and an environmental group known as Save the Sound in a venture that may restore 10 miles of sea lamprey spawning habitat on the Norwalk River, which flows into Long Island Sound?

Why this summer time will the primary large returns from stocked Pacific lampreys—a species much like sea lampreys—climb specifically designed lamprey ramps at Columbia River dams and surge into historic spawning habitat in Oregon, Washington, and Idaho?

And why, when the canal at Turners Falls on the Connecticut River is drawn down in September, will the Connecticut River Conservancy, Fort River Watershed Association, and the Biocitizen environmental faculty rescue stranded sea lamprey larvae?

The reply is ecological awakening—the gradual realization that, if the entire of nature is nice, no half could be dangerous. In their native habitat, marine lampreys are “keystone species” supporting huge aquatic and terrestrial ecosystems. They present meals for bugs, crayfish, fish, turtles, minks, otters, vultures, herons, loons, ospreys, eagles, and tons of of different predators and scavengers. Lamprey larvae, embedded within the stream mattress, keep water high quality by filter feeding; they usually entice spawning adults from the ocean by releasing pheromones. Because adults die after spawning, they infuse sterile headwaters with vitamins from the ocean. When marine lampreys construct their communal nests, they clear silt from the river backside, offering spawning habitat for numerous native fish, particularly trout and salmon.

Environmental guide Stephen Gephard, previously Connecticut’s anadromous-fish chief, calls lampreys “environmental engineers” as necessary to native ecosystems as beavers.

Marine lampreys, our elders by some 340 million years, depend upon chilly, free-flowing freshwater for spawning. They are boneless, jawless, eel-like fish with fleshy fins. They extract physique fluids from different fish by way of tooth-studded suction disks. Both sea lampreys and Pacific lampreys are extensively reviled as a result of they’re perceived as “ugly” and since sea lampreys decimated indigenous fish within the higher Great Lakes after they gained entry to these waters by way of human-built canals, almost certainly the Welland Canal that bypassed Niagara Falls. Once there, they practically worn out beneficial industrial and sport fisheries for lake trout (the biggest char species, not a real trout like rainbows, cutthroats, and browns).

By the Sixties, nonnative sea lampreys had diminished the annual industrial take of lake trout within the higher Great Lakes from about 15 million kilos to half 1,000,000 kilos. In 1955, Canada and the United States established the Great Lakes Fisheries Commission, which controls lampreys with limitations, traps, and a remarkably selective larvae poison known as TFM. Lamprey management prices $15 to $20 million a 12 months; and with out it, ongoing lake-trout restoration can be unimaginable, and populations of all different sport fish would crash.