Kira Corasanti is a reporter with Community News Service, part of the University of Vermont’s Reporting & Documentary Storytelling program.
Officials are cutting back how many lake trout are released annually into Lake Champlain after finding, for the first time in decades, sustained successful reproduction in the species — exciting news for biologists and anglers alike.
In response to rising wild reproduction, officials plan to stock about 42,000 lake trout this fall, down 50% from previous years, according to the Lake Champlain Fish and Wildlife Management Cooperative, a working group of fisheries professionals from the Vermont Department of Fish & Wildlife, the New York Department of Environmental Conservation and the U.S. Fish and Wildlife Service.
The March announcement followed a lake trout stock reduction in 2021 by a third.
“This is a good news story,” said Margaret Murphy, the lead fisheries program manager of the state fish and wildlife department. “For years we weren’t seeing any recruitment of natural populations. Now we are.”
Officials first established a stocking program in the lake in the 1950s to restore wild lake trout that had been lost because of poor water quality and habitat changes. Batches of trout would be raised in hatcheries and then released into the lake to boost the species’ numbers. After almost 70 years, researchers have found natural reproduction happening within the trout populations.
Researchers from the University of Vermont have been the lead on assessing wild populations for a couple years. At first, scientists wanted to determine whether the hatchery trout were finding areas to spawn, if they were spawning and if their eggs were hatching successfully.
“After a few years, the answer was yes,” said Ellen Marsden, researcher and fish biologist at the University of Vermont. “But many (trout) did not have any recruitment, meaning they hatched in April and May and didn’t live through the first winter. If they live through the first winter, they will live for the rest of their life.”
In 2012, the researchers noticed that about a quarter of the trout population was wild, rather than stocked. “We knew we hadn’t missed something because all of the adult fish were unclipped,” Marsden said, referring to fin-clipping, the practice of making a small cut in a trout’s pectoral fin before it leaves the hatchery as a method of tracking.
Since then, the wild trout population has increased every year. In 2020, Vermont and New York officials started to implement additional summer sampling, along with fall assessments, to look for unclipped juveniles in the spawning population.
“In 2020, we implemented indicators for stocking: If we saw a 25% wild population, we would reduce one-third. If we saw a 50% wild population, we would reduce it more,” Murphy said. “As of 2023, we have hit both of those targets.”
For fishers, this is exciting news. “Of the trout and salmon species in the lake, lake trout make up 70% of the catch,” said Matthew Trombley, a boat captain with 3rd Alarm Charters and Guide Service in Vergennes. “Sustained natural productions are always better.”
In a wild trout population, the fish respond to changes in their environment. “Stocked populations don’t have the feedback, they’ll all just starve,” said Marsden. Stocked trout are released into streams, rivers, ponds and lakes, but they are not expected to last more than a single spawning season outside of the hatchery.
Wild lake trout can live for 25 to 30 years, and they are sensitive to physical and chemical changes in their ecosystems. For researchers, they can play the role of canary in the coal mine. As indicators of lake health, the health of lake trout is usually an early warning sign of how people are treating streams, rivers and lakes.
Officials said they’re also reducing their efforts in part to avoid over-stocking. “We want to make sure we don’t add too many trout to the lake,” said Murphy. “It could cause a reduction in the forage base.”
Asked if one day Lake Champlain won’t need to be stocked at all, she said that would be the hope.
“But until then we will continue monitoring and assessing the state of the population.”