Historically, sea-run fish species like Atlantic salmon, shad, and alewife swam from Casco Bay upstream into the Presumpscot River and its tributaries to spawn before returning to the ocean.  Over time, intensive industrial uses of the river, including the construction of numerous dams to power mills, led to extirpation* of most sea-run fish species throughout the watershed.  With the removal of Smelt Hill dam at head-of-tide in 2002, over 72 miles of streams and tributaries in the lower Presumpscot watershed were reopened to the migration of sea-run fish.  Highland Lake and Mill Brook have long been viewed by resource managers as promising for re-establishment of alewives, and restoration efforts have been underway for years.

To improve alewife access into Highland Lake, the Marine Department of Marine Resources led a collaborative effort involving several partners, including the U.S. Fish and Wildlife Service, Casco Bay Estuary Partnership, Natural Resources Conservation Service, City of Westbrook, Highland Lake Association, Corporate Wetlands Restoration Partnership, Maine Department of Inland Fisheries and Wildlife, National Fish and Wildlife Foundation and local landowners, to renovate the existing fish ladder at Highland Lake dam, and modify in-stream habitat immediately downstream in Mill Brook.  The ineffective denil fishway** was improved to reduce water velocity through the baffles, making it easier for alewives to swim up the ladder, and the stream channel was altered to help direct alewives toward the bottom of the ladder.

Alewives provide important links between rivers and the sea, and reestablishment of alewives and other sea-run fish is a priority of resource managers throughout the Gulf of Maine.  In the inland freshwater and coastal marine environments, alewives provide forage for salmonids, ospreys, eagles, kingfishers, blue herons, and aquatic furbearing mammals.  Alewives are a host to native freshwater mussels, which they carry up- and down rivers in their gills.  In the marine environment, alewives are eaten by a variety of predators, such as bluefish, weakfish, striped bass, cod, pollock and silver hake.  This project provides an important step toward the restoration of these fisheries to the Presumpscot River watershed, Casco Bay estuary and Gulf of Maine.