Upstream Passage of Anadromous Species in the Lower Penobscot River, Maine; Assessing the Milford Fish Lift Using Dual Frequency Identification Sonar (DIDSON)

As part of the Penobscot River Restoration Project, Great Works (rkm 60) and Veazie (rkm 48) Dams were removed from the Penobscot River, ME, leaving Milford Dam (rkm 62) as the first impediment to fish upstream migration. Dam removal and fish passage improvements at Milford Dam are expected to increase habitat access for American shad, alewife, blueback herring, sea lamprey, and federally endangered Atlantic salmon. This anticipated increase in access is inextricably linked to successful passage at a newly constructed fish lift at Milford Dam.  Beginning in May of 2014, two DIDSON units will be placed inside the lift entrance to continuously monitor fish as they approach, enter, and are passed by the lift.  These acoustic cameras provide near video-quality sonar images that can be used to identify fish species and characterize fish behavior inside the fish lift entrance. One unit will observe how fish navigate a 180º turn in the entrance; the second will observe interactions with the movable V-shaped trap gate that leads to the lift hopper. The study will give insight into the behavior of multiple species attempting to enter the lift, and results can be used to optimize operation of the fishway.