Responses of Migratory Fishes to Passage Restoration in the Mill River, Massachusetts

Studies of the effectiveness of dam removal, particularly within southern New England, are limited. To address this information gap, we tracked the response of migratory fishes to the removal of three dams on the Mill River, Taunton, Massachusetts.  Our objectives were to (1) assess which migratory fishes utilize habitats above the former dam sites, (2) describe run characteristics, including timing, peak, and relative abundance of observed migratory species and (3) compare the run characteristics of river herring (Alosa pseudoharengus and A. aestivalis) in the Mill to the nearby Nemasket River. The first dam, Hopewell Mills, was removed in summer 2012. We employed a video monitoring system above the former dam site in 2013 and 2014. We identified at least 13 different fishes including alewife, sea lamprey (Petromyzon marinus), and white sucker (Catastomus commersonii). Alewife were the most common species observed. Although the Mill River herring run was smaller than our reference site, we noted similarities in hourly timing. Our results demonstrate that the migratory fish community of the Mill River responded rapidly to the removal of the Hopewell Mills Dam. Further work will assess the response of river herring and sea lamprey to full restoration of the Mill River.