There and Back Again: Can River Herring Reassume Their Traditional Ecological Role after Near Local Extinction?

Ecological extinction is the reduction of a species to such low levels that it no longer fills its evolved ecological roles. Prior to the removal of Edwards Dam on the Kennebec River, river herring were likely at such low abundances that they were ecologically extinct. The restoration efforts on the Kennebec River, Maine, including dam removal, resulted in the largest extant native run in the United States of over 2 million fish. A multi-disciplinary team of ecologists, geologists, economists and social-scientists set out to test whether alewife had reoccupied their assumed roles after 20 yrs of active restoration. Circa 2010 we found evidence that river herring played a reduced ecological role in the Kennebec’s freshwater and marine aquatic food webs. Response of predators, especially birds but also freshwater and marine fish, was measurable but limited in temporal duration. There was limited evidence of penetration by marine derived nutrients into the freshwater food web. River herring served an important iconic role. NGOs united behind river herring as a symbol of future ecological recovery. Residents were willing to invest modestly in restoration, although few were steeped in restoration issues. More time may be necessary for river herring to fully reoccupy ecological roles.