If you unbuild it, they will come?the fish, that is

I’m mesmerized watching them circling—a symbol of nature’s abundance and relentlessness, of the fundamental urge to create more.And yet, for more than 250 years, alewives were absent from Mill Brook and the larger river it flows into, the Presumpscot.What made the return of these fish possible was the removal, in 2002, of a dam—the unblocking of this one artery in the extensive circulatory system of the Gulf of Maine, a region of the Atlantic Ocean that extends from Cape Cod all the way to Nova Scotia.The return of alewives to Mill Brook encouraged the Presumpscot Regional Land Trust—a community-based nonprofit that stewards this area—to protect roughly six miles of the riverine corridor downstream of Highland Lake to its junction with the Presumpscot. Whitener, a biologist with the Portland-based Gulf of Maine Research Institute, has studied the life history of alewives for more than a decade,CANADAMAINECANADAMAINEAREAENLARGEDBELOWUNITEDSTATESUNITEDSTATESRange of alewife(Alosa pseudoharengus)As many as 60,000 alewives migrate annually between the marine environment where they live and the freshwater spawning location.FreshwaterBrackishSaltwaterHighlandLakeEach spring, adultalewives spend about two weeks spawning, before heading downstream.Juveniles hatch in less than one week. They take the roundtrip every year.CHRISTINA SHINTANI, DIANA MARQUESAND SOREN WALLJASPER, NG STAFFSOURCES: MAINE OSM; NOAA; IUCN;PRESUMPSCOT REGIONAL LAND TRUSTAs many as 60,000 alewives migrate annually between the marine environment where they live and the freshwater spawning location.Each spring, adultalewives spend about two weeks spawning in the lake, before heading downstream to the sea.Range of alewife(Alosa pseudoharengus)CANADAHighlandLakeAREAENLARGEDJuveniles hatch in less than one week. They take the roundtrip every year.In the protected estuary waters, juveniles beginthe marine phaseof their life cycle.In the protected estuary waters, juveniles beginthe marine phaseof their life cycle.CascoBayWESTBROOKIt takes 3-5 years for juveniles to mature into adults in the marine environment.1 miPortland1 kmCHRISTINA SHINTANI, DIANA MARQUES AND SOREN WALLJASPER, NG STAFFSOURCES: MAINE OSM; NOAA; IUCN; PRESUMPSCOT REGIONAL LAND TRUST“Despite the overall doom and gloom of climate change, and our collapsing groundfish fisheries in Maine,” he says, “it’s enheartening to see, this close to Portland, a natural system that’s recovering.” (Groundfish are those, such as cod, that spend much of their life on the floor of the ocean and are becoming scarce in the Gulf of Maine because of overfishing and warming waters.)There are now 60 to 100 alewife runs throughout the state, Whitener says, and the numbers keep going up as more dams are removed, enabling the return of not only alewives but also other migratory fish: salmon, shad, sturgeon, blueback herring, striped bass, eels.