Barrier removal in Sedgeunkedunk Stream: Sea lamprey recolonization and implications for Atlantic salmon habitat restoration

Sedgeunkedunk Stream, a 3^rd-order tributary to the Penobscot River, Maine historically supported several anadromous fish species including sea lamprey and endangered Atlantic salmon.  Several small dams constructed in the early 1800s reduced or eliminated spawning runs entirely.  As of late 2009, a small population of sea lamprey used the accessible portion of Sedgeunkedunk regularly for spawning and rearing.  Efforts to restore marine–freshwater connectivity in this system have included the construction of a rock-ramp fishway at RKM 6 in 2008 and the removal of a dam at RKM 1 in 2009.  The latter has opened up 5 km of lotic habitat.  We anticipate that semelparous sea lamprey will colonize newly accessible habitat and provide an influx of marine derived nutrients enhancing stream productivity.  Furthermore, we hypothesize that spawning sea lamprey may “condition” habitat to the benefit of juvenile Atlantic salmon via physical modification of substrate during nest construction.  Spawning lamprey were tracked in the system prior to dam removal in 2008, and collection of substrate and productivity metrics was initiated in 2009.  Comparing lamprey abundances, stream productivity and fine-scale habitat changes before and after dam removal, and with a reference stream will allow us to test our hypotheses.