Home / Environment / River Herring Return: Dam Removal Opens Patapsco River
River Herring Return: Dam Removal Opens Patapsco River
3 Nov
Summary
- River herring are returning to Maryland's Patapsco River habitat.
- The Bloede Dam removal in 2018 reopened fish passage.
- Environmental DNA and two adult fish confirm the return.
Signs of river herring returning to Maryland's Patapsco River have been detected by scientists, following the removal of the Bloede Dam in 2018. This dam had been a long-standing barrier to fish migrating upstream from the Chesapeake Bay for over a century. The $9.3 million project, a collaboration involving NOAA and other organizations, aimed to restore vital fish habitats.
Using environmental DNA (eDNA) analysis, researchers found a significant increase in the likelihood of detecting river herring eDNA upstream of the former dam site. Within three years of the dam's removal, the chance of finding alewife eDNA rose to 5 percent, and blueback herring eDNA to 13 percent, compared to zero before. In 2021, biologists confirmed the return by spotting one adult alewife and one blueback herring.
While these findings are encouraging, representing an early win for habitat restoration, scientists emphasize that it's not yet proof of population recovery. The study noted no increase in egg numbers or detection of tagged fish upstream. Continued long-term monitoring is crucial to fully assess the impact on river herring populations. This restoration effort extends beyond the Bloede Dam, with previous projects opening over 65 miles of habitat for various fish species and eels.
