Fish Community Response to a Small-Stream Dam Removal in a Coastal Maine Tributary
Sedgeunkedunk Stream, a 3rd-order tributary to the Penobscot River, Maine historically supported several anadromous fishes including Atlantic salmon Salmo salar, alewife Alosa pseudoharengus, and sea lamprey Petromyzon marinus. However, two small dams constructed in the 1800s reduced or eliminated s...
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DigitalCommons@UMaine
2012
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| Online Access: | https://digitalcommons.library.umaine.edu/etd/1853 https://digitalcommons.library.umaine.edu/context/etd/article/2882/viewcontent/Fish_Community_Response_to_a_Small_Stream_Dam_Removal_in_a_Coast2.pdf |
| Summary: | Sedgeunkedunk Stream, a 3rd-order tributary to the Penobscot River, Maine historically supported several anadromous fishes including Atlantic salmon Salmo salar, alewife Alosa pseudoharengus, and sea lamprey Petromyzon marinus. However, two small dams constructed in the 1800s reduced or eliminated spawning runs entirely. In 2009, efforts to restore marine-freshwater connectivity in the system culminated with removal of the lowermost Mill Dam thus providing access to an additional 4.7 km of lotic habitat and unimpeded passage into the lentic habitat of Fields Pond. In anticipation of these barrier removals, we monitored stream fish assemblages in strategically-placed impact and reference sites with backpack electrofishing surveys twice yearly since 2007. Results as of August 2011 indicated that density, biomass and diversity of the resident fish assemblage increased at all impact sites upstream of the 2009 dam removal, and no distinct changes in these metrics occurred at unaffected reference sites. Additionally, we documented recolonization and successful reproduction of three anadromous species in previously inaccessible upstream reaches. Three age classes of juvenile Atlantic salmon including emergent young-of-the-year fry were observed approximately 2-km upstream of the former Mill Dam in 2011. Adult alewives were intercepted at upstream impact sites en route to previously inaccessible habitat in Fields Pond, and their progeny were observed exiting the system en route to the Atlantic Ocean during our late-summer sampling in 2011. Finally, sea lamprey larvae were encountered in previously inaccessible upstream reaches during electrofish surveys in 2011. Sea lampreys reliably utilized accessible downstream habitat prior to the 2009 dam removal, and were therefore chosen as a focal species to quantify recolonization. During spawning runs of 2008 through 2011 (pre- and post-dam removal), individuals were marked with PIT tags and their activity was tracked with daily recapture surveys. Open-population ... |
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