There was a time when landlocked Atlantic salmon were abundant in Lake Champlain and its tributaries. But for a century and a half these salmon were not reproducing naturally in the Lake Champlain basin. Now scientists are cautiously optimistic things might be changing.

This year, wild-born salmon fry have been found in the Lake Champlain basin (fry is the name for young salmon after they've hatched, lost their yolk sac and can swim freely). Jadziah Hannon-Moonstone, a biological technician for U.S. Fish and Wildlife based in Vermont, told Vermont Edition that the fry were found this year in New York's Boquet River.

Finding fry in the basin is a big deal; it's just the third time in the last 150 years that it has happened. The previous two times were in 2016 and 2017.

According to Hannon-Moonstone, the fry discovery is significant on a couple of levels. First, it means fish are able to actually reach these prime areas of habitat to spawn. For many years, dams and other barriers prevented adult fish from traveling upstream to spawn.

But something that's "an even bigger deal," Hannon-Moonstone said, is that the fish are surviving to the fry stage.

"In the Champlain Valley — as well as many other places, but particularly here — we've been concerned about particles that are in the water," Hannon-Moonstone said. "Salmon create their nests, ... they bury the eggs and then they cover them in gravel. And then, when there's fine particles in the sediment, it basically covers up all the little holes that the gravel creates for airflow and it entombs the eggs, so the eggs basically suffocate there and are never able to hatch."

There are no areas in the state that have sustained wild populations of Atlantic salmon, and most waterways in the Champlain basin and elsewhere are stocked with salmon reared in captivity. A popular fish among anglers, the restocking program is robust. But Hannon-Moonstone said fisheries biologists have kept parts of the Boquet River and Winooski River free of stocked fry for several years to monitor for fry "for the eventual goal of natural reproduction in systems like the Boquet [River] and the Winooski River."

Fry had not been seen in these waterways in 150 years until 2016, when they were first found in the Winooski River. They were also found there in 2017. Hannon-Moonstone said it's tricky to track these fry as they grow because they're indistinguishable from stocked salmon.

In 2018, no fry were found anywhere in the basin. So Hannon-Moonstone said this year's discovery in New York has been a welcome development for her and her colleagues.

"I am an enthusiastic fisheries biologist, and I love seeing them — and many of my co-workers are just enthused about it and conservationists are really enthused about it," she said.

One last thing: just how do biologists go about searching for these teeny, tiny fry?

"We have snorkel masks on," Hannon-Moonstone said, "and we're basically army-crawling through the river for hours."

Broadcast live on Monday, Aug. 5, 2019 at noon; rebroadcast at 7 p.m.