CONNECTING RIVER MORPHOLOGY TO FISH HABITAT IN THE CONTEXT OF DAM REMOVAL: THE PENOBSCOT RIVER RESTORATION PROJECT

The recent removal of two large dams on the Penobscot River will not only change river morphology but has also made 14 kilometers of river available to anadromous fish. This river rehabilitation project restored 100% of the historic habitat for the endangered shortnose sturgeon (Acipenser brevirostrum). This species has been documented foraging and wintering in the Penobscot River. In other shortnose sturgeon rivers, freshwater reaches also provide habitat for spawning. Spawning habitat is typically characterized as having water depths of 1.2 to 10.4 m, water velocities from 0.4 to 1.8 m/s, and bottoms composed of cobble, gravel, boulder, and ledge. However, since monitoring began in 2007, sturgeon spawning has not been documented in the Penobscot. With the removal of the Great Works and Veazie dams in 2012 and 2013, access to potential spawning areas has increased. This study was conducted to determine the suitability of that newly available habitat for spawning. Prior to the dam removals, a two-dimensional hydrodynamic model was used to quantify the amount of suitable spawning habitat, based on water velocity and depth, in the reaches upstream of the dams. Since bottom substrate is another important variable influencing spawning habitat suitability, current work aims to incorporate bottom type into the previously developed model. Field collection of bottom substrate via pebble counts began in the summer of 2014 and will continue in 2015. To date, 27 transects were conducted on the east and west shore of the river between the old Veazie dam site and Orono, spanning approximately 9.4 river kilometers. Substrate data, along with side scan sonar and underwater video data, will be incorporated into the velocity and depth model to provide more detail about the distribution and abundance of suitable habitat for sturgeon spawning in the newly available reaches of river. Concurrent monitoring of fish movements using acoustic telemetry may allow us to verify spawning habitat, should the sturgeon choose to spawn in the Penobscot in spring 2015. The resulting maps of suitable habitat will allow for more efficient targeting of future restoration and monitoring efforts on the Penobscot River.