For most of the last century, the alewife was a fish in retreat. Every spring, river herring push up from the ocean into the lakes and ponds where they hatch, and in Maine, one dam after another had blocked the way - until the runs that once turned rivers silver had dwindled to a memory. By 1994, the inland catch had fallen from a historical average of about 3 million pounds a year to just 150,000 [1].
Then the state started taking the dams out. From 1999 to 2016, a wave of removals - including two dams on the Penobscot River - reopened hundreds of miles of spawning habitat, and a 2012 moratorium on offshore alewife fishing eased the pressure from the other direction [1]. The fish did the rest.
In 2025, more than 20 million river herring ran up Maine's rivers - the highest count in decades [1]. A collapse that took most of a century to bottom out has, in a single generation of restoration work, reversed into one of the clearest fisheries comebacks in the country.
The alewives are not the only ones that benefit. River herring are a keystone forage fish: their spring runs feed ospreys and bald eagles, striped bass and cod, otters and seals, and they carry ocean nutrients far up into freshwater systems that had gone hungry for them. Bring the fish back, and a whole food web comes back with them.
None of it required a new technology or a grand plan - just the removal of walls that should not have been there, and the patience to let a river remember what it used to do. Twenty million fish is what that looks like when it works [1].
