Last November on the Farmington River in Connecticut, fisheries biologists discovered three nests of Atlantic salmon eggs, marking the first known wild spawning of Atlantic salmon on the river since the Revolutionary War, when dams and industrial waste wiped out the salmon population on the Connecticut River and its tributaries.

This spring those eggs are expected to hatch and already are reviving talk of yet another effort to restore wild Atlantic salmon to the river, despite the odds. There have been many failed attempts.

Before they found the nests, the biologists saw five adult Atlantic salmon swimming up fish ladders past the Rainbow Dam on the lower Farmington, evidence that at least a few salmon are attempting a comeback.

“It’s a great story, whether it’s the beginning of something great or the beginning of the end,” John Burrows, of the Atlantic Salmon Federation, told Nate Schweber, a reporter for Al Jazeera America.

Before European colonization, the Connecticut River teemed with annual runs of 50,000 Atlantic salmon, the most in North America, biologists told Al Jazeera.

In the late 1800s the first salmon-stocking program failed, according to the news organization. In 2012, after nearly a half-century of work and an investment of $25 million, the federal government and three New England states pulled the plug on another attempt to resurrect the prized fish.

The quest to restore Atlantic salmon in the Connecticut River began in earnest in the mid-1960s. The federal government and New Hampshire, Vermont, Massachusetts and Connecticut joined forces to curb pollution in the river that the states share and build passageways — or “ladders” — around some of the 2,500 dams that blocked the river and its tributaries in the 11,250-square-mile Connecticut River watershed.

Through this restoration program, a few thousand 2-year-old, hatchery-raised Atlantic salmon were stocked in the river in 1967, but they soon died or swam out to sea and did not return.

The stocked salmon continued to die off through the early 1970s. Gradually scientists began to learn about different strains of salmon. In 1976 the program acquired Atlantic salmon eggs from the Penobscot River in Maine, the closest surviving population both physically and genetically, according to the Al Jazeera report.

In 1978, 90 fish from the Maine strain made the 2-year, 6,000-mile migration to the food-rich Labrador Sea off Greenland and returned to the Connecticut River. In 1981 more than 500 salmon returned, and biologists began catching and breeding the salmon that returned to the river to develop a strain that would follow genetic commands to migrate out from and back to the river.

The recovery was short-lived. A “perfect storm” of erratic ocean currents, warming Atlantic seas, colder and saltier waters off Greenland, and unhealthy populations of the salmon’s favorite foodfish — symptoms of global climate change — interrupted the recovery, scientists told Al Jazeera.

In 2001 only 40 Atlantic salmon returned to the Connecticut River, and 44 returned the next year — a declining return on investment. In 2011 Hurricane Irene caused $14 million in damage to the facility where the salmon eggs were hatched, and the following year the U.S. Fish and Wildlife Service withdrew funding for the restoration program.

— Jim Flannery