State officials say that an increase in the number of alewives returning to Maine's rivers could be helping to boost populations of Atlantic salmon.
The Maine Department of Marine Resources says nearly 1,500 salmon have returned to dams in Orono and Milford along the Penobscot River this year, and about 150 have been counted at two dams along the Kennebec.
Both numbers are the most since at least 2015.
Sean Ledwin, the director of the department's bureau of sea run fisheries and habitat, said the state has also seen the largest run of river herring in the Penobscot River this year -- which provide a kind of shield that protects Atlantic salmon from predators.
"They call that prey buffering. So they have more prey around. And then rare species like Atlantic Salmon escape, in the predator gauntlet that is the Lower Kennebec and Lower Penobscot Rivers," Ledwin said.
Ledwin said other factors can also play a role in population numbers, including a new stocking program on the Kennebec River from U.S. Fish & Wildlife Services.
Ledwin added that temporary shutdowns of Kennebec River dams two years ago may have also improved survival rates.
"And so this is the first year where some of those returns are coming back. So some of those turbine shutdowns probably increased survival of fish coming down the river, and getting out to sea," Ledwin said.
Ledwin said that while the numbers are encouraging, they're still far below historical populations of the species, which at one point numbered in the hundreds of thousands.
