Finally, after years of Maine politicians ignoring the science that supports the benefits of alewives returning to the upper reaches of the St. Croix River, they have acted on that scientific knowledge. On Wednesday, the Maine Legislature passed LD 72, a bill sponsored by Rep. Madonna Soctomah of the Passamaquoddy Tribe, to grant the fish unconstrained passage.

The Maine House voted 123-24 and the Maine Senate voted 33-0, giving the bill the two-thirds majority support it needed to pass as an emergency measure. It will become law immediately if Gov. Paul LePage signs it, prompting the state to ensure that by May 1, the fish passage on the Woodland and Grand Falls dams are operating and not blocking the flow of fish.

Alewives, a type of river herring, spend most of their life at sea but return each year to freshwater streams during the spring — late April to early June — to spawn. Females deposit thousands of eggs in lakes and ponds, which then hatch in a few days. The young fish migrate to the sea from mid July to early November, and the whole process repeats the following year.

Alewives are an important part of the larger ecology. They protect Atlantic salmon by serving as alternative prey for osprey, eagles and seals. Nearly everything eats the fish, including tuna, cod, haddock, halibut, brook trout, lake trout, landlocked salmon, pike, white and yellow perch, seals, whales, otters, foxes and turtles. The native fish species also makes good bait for lobster fishing.

But for years, many bass fishing guides have opposed allowing alewives to return to waters north of the Grand Falls Dam in Washington County. They have referred to the mid to late 1980s when the alewife population increased and the bass population diminished, even though there is no evidence the two events were connected.

Still, in 1995 the Maine Legislature voted to close the Woodland and Grand Falls fishways, and the alewife population plunged to 900 fish in 2002, from 2.6 million in 1987. The law was amended in 2008 to open the fishway at Woodland, but alewives still cannot reach 98 percent of their traditional spawning ground.

Many studies have shown that alewives and bass coexist, and bass even eat alewives. If anything, a 10-year study found, a lake drawdown made the bass’ protective rock habitat disappear and forced the bass to compete for food and habitat with other fish. The Legislature’s vote on Wednesday is a recognition of the science.

The original closure of the St. Croix was based on “myth and misinformed rhetoric,” John Burrows, director of the New Brunswick Programs for the Atlantic Salmon Federation, told the Legislature ’s M arine Resources Committee March 25. “The fact that 98 percent of the river has remained closed when there is substantial scientific support for restoring alewives is simply astounding. To our members, this is the greatest ecological injustice to occur in the state of Maine in generations, and there is no reason to keep the river closed.”

Burrows hit the point spot on. LePage should sign the bill as soon as possible and let the alewives run.