Transport, Dam Passage, and Size Selection of Adult Atlantic Salmon in the Penobscot River, Maine

Abstract

Prior to 2012, returning adult Atlantic Salmon Salmo salar had to pass through fishways at three dams in the lower section of the Penobscot River, Maine: Veazie Dam (river kilometer [rkm] 48; removed in 2013), Great Works Dam (rkm 60; removed in 2012), and Milford Dam (rkm 62). To facilitate better passage through the lower river, a fish transport program was implemented in 2010 and 2011. Fish were captured at Veazie Dam and were either transported by truck above Milford Dam (TRKD group) or released into the head pond above Veazie Dam (run-of-the-river [ROR] group). To assess the efficacy of transport, we used PIT telemetry to compare the performance and passage of TRKD and ROR fish based on their (1) success in reaching one of the three dams upstream of Milford Dam, (2) time taken to reach an upstream dam (transit time), and (3) success in passing that upstream dam. In both years, the percentage of fish detected at upstream dams was higher for the TRKD group (82.4% in 2010; 78.6% in 2011) than for the ROR group (41.3% in 2010; 22.4% in 2011). In addition, median transit time was faster for TRKD fish (7 d in 2010; 5 d in 2011) than for ROR fish (23 d in 2010; 25 d in 2011). However, passage success through the upstream dams did not differ between the two release groups. Our analysis also revealed a strong, negative size-selective force on dam passage: larger fish were consistently less likely to successfully pass dams than smaller fish. Finally, environmental conditions also influenced passage success. Our analysis shows that the transport of adult Atlantic Salmon can be an effective means by which to increase migration success in systems where upstream passage is poor.

Received May 27, 2014; accepted September 17, 2015

ACKNOWLEDGMENTS

This work was part of a larger monitoring program administered by the Penobscot River Restoration Trust and was funded in part by an American Recovery and Reinvestment Act cooperative agreement with the National Oceanic and Atmospheric Administration (NOAA) Restoration Center. Additional financial support was provided by the University of Maine and the U.S. Geological Survey's Maine Cooperative Fish and Wildlife Research Unit. We thank the MDMR, NOAA Fisheries, and U.S. Fish and Wildlife Service for providing technical expertise. We are grateful to the Penobscot River Restoration Trust, Black Bear Hydro, Brookfield Power, True Textiles, and the Town of Dover-Foxcroft for allowing and facilitating access to the dams. Mention of trade names or commercial products does not imply endorsement by the U.S. Government. This work was conducted under Institutional Animal Care and Use Committee Protocol A2011-06-05 (University of Maine).