A behind-the-scenes look at the wild revival of Lake Champlain trout

Scientists, fisheries managers keep watchful eye of growing success of lake trout recovery. Here’s a look at how they do it.

By Zachary Matson

After decades of stocking lake trout in Lake Champlain, researchers and fisheries managers are starting to see something rare in the word of native fish restoration: lake-born, wild, trout thriving in the region’s largest lake.

As the wild population showed signs of persistence, managers agreed to cut stocking levels and did so again last year. Stocking levels this fall and spring are targeted at 41,000 fish, about a quarter of historic levels.

Now that they are pulling back on stocking, those managers are monitoring how the trout population responds and determining whether, and when, to eliminate stocking altogether.

The Adirondack Explorer this summer reported on the backstory of this wild revival of the lake’s top predator. Here’s that story — in photos.

Starts in the hatchery

Until recent stocking cuts both New York and Vermont contributed hatchery-raised fish to the lake’s stocking program. New York’s stocking was eliminated during recent cuts as a logistical efficiency. Now, fish stocked into the lake are all raised at the Vermont Fish and Wildlife Department’s Ed Weed Fish Culture Station on Grand Isle.

Paige Blaker, the hatchery’s fish culture supervisor, collects about twice the number of eggs as she needs fish from the state’s lake trout broodstock in Salisbury and transports them in a pair of Igloo coolers. About 450 adult trout kept in Salisbury are the parents of the 41,000 trout slated to be stocked this year. The eggs are kept in stacks of incubation trays before they hatch and start to grow.

The newly-hatched fry are moved to larger tanks tied into an efficient aquaculture system that recirculates and cleanses the water. At first, the fish are fed nearly every two hours, with feedings gradually tapering to three times a day.

In the spring, once the young trout have grown a few inches, hatchery staff use a forklift to move the trout from the circular tanks to concrete raceways in a large covered warehouse space. The fish are grown to about seven inches before being stocked in the lake in the fall and spring, many directly off ferries between New York and Vermont.

Counting forage fish

To monitor the health of the lake trout population, researchers also study the lake’s forage fish base. Forage fish, the smaller fish that lake trout feed on, are an important link in the food web. Too few forage fish could threaten lake trout, while too many lake trout could crash the forage base.

Scientists at the University of Vermont this summer worked to establish a new study of forage fish in Lake Champlain.

UVM graduate student Shelby Scarfo is leading the new forage fish study, working alongside longtime trout researcher Ellen Marsden, who retired from teaching at UVM this year.

Scarfo, Marsden and their crew went trawling in April from UVM’s new state-of-the-art research vessel, the Marcelle Melosira. They were still working out the logistics of conducting a new study from a new boat, but over the season collected hundreds of samples of forage fish, which Scarfo will weigh, measure and determine how to translate into large assessments of the forage fish populations in the lake.

Marsden, considered the lake’s leading trout expert, and her colleagues for years searched for wild trout without success. In 2015, though, they found the first cohort of juvenile trout in the lake with their fins intact. Since hatchery fish get their fins clipped before being stocked, researchers now that fish with all their fins in place were likely born in the lake. The population of unclipped fish has been gradually climbing in the decade since.

“Every sign points to this being a recovery, not an accident,” Marsden said. “I spent 20 years trying to figure out what went wrong, and now we are trying to figure out what went right.”

Finding the adults

During the 1990s fisheries managers in New York and Vermont conducted surveys of Lake Champlain to see how stocked lake trout were doing and whether and wild lake trout hadn’t taken hold in the lake. They dropped special nets into the lake for 24 hours, ensnaring trout in different sized mesh nets, so-called gillnets.

Vermont Fish and Wildlife in 2020 re-instituted the gillnet survey to track the progress of wild trout known at the time to be surviving in the lake.

The survey, conducted in the same spots as the 1990s in the north, south and central parts of the lake, over five years has shown a steady increase in the proportion of and rate of wild trout caught throughout the lake.

The survey is scaly, slimy, bloody and, for the fish, deadly work. Researchers cap the number of fish collected in each section of the lake at 100, the fewest fish that can be sacrificed in the name of reliable data.

The trout are weighed, measured, checked for sea lamprey wounds, and sliced open to determine sex and stomach contents. The wildlife agency staff remove each fish’s jawbones, which are later cut into wafer-thin segments that help age the fish.

They also record whether the fish has a clipped fin (and was raised in a hatchery) or has all of its fins in place (and was born in the lake).

On the hunt

Lake trout use Lake Champlain’s rugged waterscape to their advantage as they stalk prey from the depths. They hunt for food near shoals and underwater islands, where they can ambush their next meal. 

That’s where Scott Thurber, who charters fishing tours out of Plattsburgh, looks for lake trout.

Thurber has been fishing Lake Champlain for over 50 years, learning from his grandpa who fished the lake when there were no lake trout. After retiring as a Saranac Lake police officer, Thurber started his charter business, Irish Raider Outfitters. When he catches a fish, Thurber immediately inspects the fins, hoping he pulled in a wild one before releasing it. He said he is catching more and more unclipped lake trout. To his eye, they shine brighter with more distinctive coloration than their hatchery-raised counterparts.