HUNTINGTON, Vt. (AP) — For the first time in about 150 years, landlocked Atlantic salmon are once again swimming up some Lake Champlain tributaries in Vermont and New York to spawn in gravel banks, biologists say.
It hasn't come easy, and the process will require continued human intervention to make sure the salmon that hatch in Vermont's Winooski River or New York's Boquet River can make it to the lake and then return when it's their time to reproduce.
Biologists call it a success story produced by a better understanding of the salmon, reduction in the numbers of parasitic sea lamprey in Lake Champlain, improved water conditions in the tributaries, and help the fish got to navigate around dams responsible for loss of the original salmon in the 1800s.
"Salmon are a great indicator species for looking at how well we are doing," said Bill Ardren, a senior fish biologist with the U.S. Fish and Wildlife Service who works on the Lake Champlain salmon restoration program.
"So when you start to see salmon reproducing naturally, and the juveniles surviving, that is starting to show that we are making progress in restoring that aquatic ecosystem," he said.
The biologists have worked with their counterparts in the Pacific Northwest to better understand the fish.
The salmon restoration program for Lake Champlain began in the 1970s when the U.S. Fish and Wildlife Service and the wildlife agencies from Vermont and New York started stocking salmon and lake trout. In the early years, the program was hampered by the presence of invasive sea lamprey that populated the area via 19th-century canals.
A long-term sea lamprey control program began in 2002, and now sections of the lake are treated every fall to kill them.
"Initially we had no fish coming back to our rivers, but now that the wounding rates are lower, we have more fish out there surviving; the numbers of salmon returning to our streams and rivers along the lake have increased dramatically," said Nicholas Staats, a federal fish biologist.
In autumn 2014, for the first time in about 150 years, biologists discovered salmon redds, areas where the fish used their tails to dig holes in the gravel where eggs were laid, in the Huntington River near Richmond. In spring 2016, the biologists discovered young salmon that came from eggs laid in autumn 2015.
Now broad sections of the Winooski River, just downstream from the Huntington, are ideal salmon spawning grounds. Ardren, Staats and others hope more salmon, averaging 22 inches (56 centimeters) long and weighing up to 13 pounds (5.9 kilograms) and will return there at the end of October to continue the cycle.
To make that happen, the state and federal government have been working to carry returning salmon above three Winooski River dams to make it possible for them to reach their spawning grounds. Two years ago, a dam was removed from New York's Boquet River, but biologists are still helping the fish upstream.
This fall's run is expected to begin later this month.
There is still a long way to go. In Vermont, biologists stock about 30,000 young fish each year. Over the past several years, the biologists have watched returning fish increase from between 10 and 20 a year to between 100 and 200.
Biologists consider that a good number and they expect it to increase.
Last week, Staats and four fish experts from the Vermont Department of Fish and Wildlife spent the morning on the Huntington catching some of the salmon that were stocked last year. The fish, caught with an electrofishing system, were released after they were measured.
"This year we found 16 salmon in this stretch of the river from last fall's stocking, which is pretty good," Staats said.