Once, the sight of thousands of adult Atlantic salmon migrating upstream forecast the coming of winter in New England. Now, what few do make the trek can be counted on two hands in some Maine rivers (see related story).

Atlantic salmon fry, hatching in spring from eggs laid in autumn, spend anywhere from one to five years in the rivers of their birth, growing more slowly in the northern reaches of their territory. When large enough, they begin a process called smoltification, adjusting their internal systems to salt water to prepare for migration. Emigrating out to sea in the spring, they swim thousands of miles to winter off Greenland. After spending a few years maturing at sea, they use a keen sense of smell to return to their natal rivers to spawn.

Native to nearly every major river between the Housatonic in Connecticut and the St. Croix on the Canadian border, salmon were an integral part of life for Native Americans and American settlers, and they continue to play a vital – but increasingly limited – role in the ecosystem today.

The impacts of hydropower dams, over-fishing, and water pollution were seen as early as the 1800s, with the extinction of the Southern New England salmon. By the mid-1970s, only a few hundred adults were returning to Maine. Now, with pollution abating and fishing for salmon prohibited, restoring the salmon’s historical range by providing safe passage around dams is the key to returning the “king of fish” to its former prominence.