Anadromous Sea Lampreys Recolonize a Maine Coastal River Tributary after Dam Removal

Abstract

Sedgeunkedunk Stream, a third-order tributary to the Penobscot River, Maine, historically supported several anadromous fishes, including the 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 dam, thus providing access to an additional 4.6 km of lotic habitat. Because Sea Lampreys utilized accessible habitat prior to dam removal, they were chosen as a focal species with which to quantify recolonization. During spawning runs of 2008-2011 (before and after dam removal), individuals were marked with PIT tags and their activity was tracked with daily recapture surveys. Open-population mark-recapture models indicated a fourfold increase in the annual abundance of spawning-phase Sea Lampreys, with estimates rising from 59 ± 4 ( N ± SE) before dam removal (2008) to 223 ± 18 and 242 ± 16 after dam removal (2010 and 2011, respectively). Accompanying the marked increase in annual abundance was a greater than fourfold increase in nesting sites: the number of nests increased from 31 in 2008 to 128 and 131 in 2010 and 2011, respectively. During the initial recolonization event (i.e., in 2010), Sea Lampreys took 6 d to move past the former dam site and 9 d to expand into the furthest upstream reaches. Conversely, during the 2011 spawning run, Sea Lampreys took only 3 d to penetrate into the upstream reaches, thus suggesting a potential positive feedback in which larval recruitment into the system may have attracted adult spawners via conspecific pheromone cues. Although more research is needed to verify the migratory pheromone hypothesis, our study clearly demonstrates that small-stream dam removal in coastal river systems has the potential to enhance recovery of declining anadromous fish populations.

Dispersal and productivity of Chinook (Oncorhynchus tshawytscha) and coho (Oncorhynchus kisutch) salmon colonizing newly accessible habitat

“…Dams are ubiquitous across the landscape of the United States (Graf 1999), and there is an increasing awareness that removal of ageing dams and provision of fish passage provide special opportunities to conserve migratory fishes (Burdick and Hightower 2006;Catalano et al 2007;Hogg et al 2013;Pess et al 2014). In the US Pacific Northwest, dams and other structures have severely reduced the quantity and quality of spawning and rearing habitats accessible to Pacific salmon (Oncorhynchus spp.…”

Rivers in the Critical Zone

“…The cumulative effects of dam removal in the United States have largely been positive, with measurable increases in the populations of fish and other river organisms (Hogg et al, 2013). At the same time that dams are being removed or operated to allow environmental flow releases in the United States and Europe, substantial numbers of very large dams are being built in Asia, Africa, and Latin America (Wohl, 2011).…”

Sea LampreyPetromyzon marinusBiology and Management Across Their Native and Invasive Ranges: Promoting Conservation by Knowledge Transfer

“…These obstructions severely fragment their habitats and thus can strongly restrict the riverine habitats available 225 to spawning adults (Lucas et al, 2009), as well as impede the downstream movement of larvae/juveniles (Nunn and Cowx, 2012;Hogg et al, 2013). The blockage of migratory routes can thus significantly affect the lifetime fitness of P. marinus, impacting their population growth 230 and distribution, spawning success and recruitment, and affecting their vulnerability to fishing and predators (Andrade et al, 2007;Klamath River Expert Panel, 2010;Mateus et al, 2012).…”

“…These areas are frequently 285 modified and/or destroyed by various anthropogenic activities, including building of dams or weirs, sand extraction, channelization, dredging, dewatering as well as the management for other fish (Oliveira et al, 2004;Mateus et al, 2012;Hogg et al, 2013). For example, 290 dredging and channelization can directly impact larvae and ammocoetes by their removal, and indirectly by reducing the availability of nursery habitat (OSPAR Commission, 2009;Mateus et al, 2012).…”

“…The absence of a unidirectional current can disorient migratory adults or increase their passage time through bar-310 riers (Johnson et al, 2015). Finally, changing flow regimes can alter thermal regimes, potentially interfering with the timing and success of migration and spawning, as well as embryonic development and ammocoete survival and growth (Hogg et al, 2013).…”