Movements of Prespawn Adult Atlantic Salmon Near Hydroelectric Dams in the Lower Penobscot River, Maine

Abstract

Acoustic telemetry was used to assess riverine behavior and passage success for prespawn male adult Atlantic salmon Salmo salar in the lower Penobscot River, Maine, in 2005 (n = 10) and 2006 (n = 25). Only 3 of 10 (30%) and 2 of 25 (8%) tagged Atlantic salmon successfully passed all three dams between the head of tide and presumed spawning habitat in 2005 and 2006, respectively. Migrants that failed to pass the second upstream dam frequently fell back into the estuary (3 of 4 in 2005; 17 of 23 in 2006), and few successfully reascended Veazie Dam at the head of tide. Fallback behavior was associated with temperatures exceeding 22°C and may reflect a strategy for coping with thermal stress and migratory delays. Atlantic salmon were also observed to actively seek out thermal refuge near one of the dams. Passage data were compared with results from previous telemetry studies that used Carlin tags and radio telemetry from 1987–1990 and 1992, and passive integrated transponder tags from 2002–2004. For all 10 years of study combined, median passage success was 64, 72, and 93% for the three dams. While 2006 may represent an uncommonly poor year for upstream passage at these dams, median cumulative passage past two of these dams was only 71% and ranged from 8% to 87% among years. Study results indicate that poor upstream passage severely limits migratory success in this system, particularly during periods of high discharge. Planned removal of two of these lower river dams is expected to improve migratory success for adult Atlantic salmon in the Penobscot River system.

What is “fallback”?: metrics needed to assess telemetry tag effects on anadromous fish behavior

“…Although ''fallback'' in the alosine literature is defined as unnatural downstream movement related to tag effect and handling, salmonid telemetry studies rarely link ''fallback'' to tag effects or handling (Bernard et al, 1999;Makinen et al 2000;Holbrook et al, 2009). Often the downstream movements of upstream migrating salmon are described as a purposeful behavior in response to the environment, obstacles, or a mechanism of homing .…”

“…Often the downstream movements of upstream migrating salmon are described as a purposeful behavior in response to the environment, obstacles, or a mechanism of homing . These complex behaviors include overshooting of natal systems (Naughton et al, 2006), exploratory movements (Keefer et al, 2008), seeking alternate routes, waiting for appropriate conditions (Thorstad et al, 2005;Holbrook et al, 2009), disorientation in certain hydraulic conditions (Naughton et al, 2006), being swept over dams (Matter & Sandford, 2003), or varying sensitivity in distinct migratory phases (Makinen et al, 2000;Jokikokko, 2002). Aberrant movement in salmonids has not been explicitly related to ''fallback'' or tag effect (Young et al, 2006); for example, when radio tags were used to examine the effect of catch-and-release on adult Atlantic salmon (Salmo salar), uncharacteristic up and downstream movements of radiotagged fish observed post-release were attributed to angling (Thorstad et al, 2003).…”

Seasonal residency and movement patterns of two co‐occurring catadromous percichthyids within a south‐eastern Australian river

“…Historically, M. novemaculeata were found in the Shoalhaven River and tributaries above Tallowa Dam, prior to its construction in 1976 (Bishop 1979). In the current study, acoustic telemetry and tagging technologies (Heupel et al 2006;Holbrook et al 2009) have been applied to both species, which has generated long-term data on their behaviour, including seasonal and annual trends in population movement, as well as interactions between species. Therefore, it is possible that the presence of the dam may have implications on the residency and movement of M. novemaculeata.…”

Upstream Movements of Atlantic Salmon in the Lower Penobscot River, Maine Following Two Dam Removals and Fish Passage Modifications

“…In the summers of 2012 and 2013, the Great Works and Veazie dams, respectively, were removed from the main stem of the Penobscot River (Figure 1). Upstream passage success for Atlantic Salmon at both dams was annually variable and often poor prior to removal (43-100% at Veazie Dam, 12-95% at Great Works Dam; Holbrook et al 2009), so the demolition of these two dams was anticipated to be a significant step in improving upstream passage for adult salmon in the system.…”

“…After the removal of the Great Works and Veazie dams, Milford Dam has become the downstream-most dam on the main stem of the Penobscot River, hence, the first barrier for upstream migrating anadromous fish. Passage success at Milford Dam through a Denil fishway was relatively high prior to the PRRP (>80%; Holbrook et al 2009), and delays were short compared with the other dams in the lower river (Shepard 1989;Holbrook et al 2009). In April of 2014, a new fish lift and handling facility designed to pass Atlantic Salmon, Sea Lamprey Petromyzon marinus, Alewives Alosa pseudoharengus and Blueback Herring A. aestivalis (collectively referred to as "river herring"), and American Shad A. sapidissima, was completed at Milford Dam.…”