Exploring the Threats of Dams and Ocean Conditions: In-River Movements and Ocean Growth of Atlantic Salmon (Salmo salar) from Maine's Rivers

• Main Author: Izzo, Lisa K
• Format: Text
• Language: unknown
• Published: DigitalCommons@UMaine 2016
• Subjects: Atlantic Salmon; fish passage; endangered species; telemetry; Penobscot River; age and growth; Natural Resources and Conservation; Terrestrial and Aquatic Ecology; Atlantic salmon; Salmo salar
• Online Access: https://digitalcommons.library.umaine.edu/etd/2479; https://digitalcommons.library.umaine.edu/cgi/viewcontent.cgi?article=3545&context=etd

Substantial declines of anadromous Atlantic Salmon Salmo salar have occurred throughout the range of the species, with many populations at the southern extent of the distribution being extirpated or endangered. While Maine is the last state in the country where adult Atlantic Salmon return to rivers each year to spawn, numbers have decreased dramatically in recent decades, with typically less than 2,000 spawners returning to all Maine's rivers combined. The complex life history of this species, which involves a juvenile freshwater phase followed by a marine phase that can last one to five years before returning to freshwater to spawn has exposed Atlantic Salmon to a series of threats that have contributed to their continued decline. These threats include, among others, dams and changing ocean conditions that can influence marine mortality. This thesis focuses on those two threats by using radio telemetry to assess upstream passage of adult salmon in the lower Penobscot River and scale analysis to interpret ocean growth patterns in relation to ocean conditions. The Penobscot River Restoration Project (PRRP), completed in 2016, involved an extensive plan of dam removal, increases in hydroelectric capacity, and fish passage modifications to increase habitat access for diadromous species. As part of the PRRP, Great Works (rkm 59) and Veazie (rkm 46) Dams were removed, making Milford Dam (rkm 61) the first impediment to federally endangered Atlantic Salmon and other diadromous species. In 2014 and 2015, a total of 73 adult salmon were radio-tagged to track their upstream movements through the Penobscot River to assess potential delays at 1) the dam remnants, 2) the confluence of the Stillwater Branch and the main stem of the Penobscot River below the impassable Orono Dam, and 3) the Milford Dam fish lift (installed in 2014). Movement rates through the dam remnants and the Stillwater confluence were comparable to open river reaches. Passage efficiency of the fish lift was high in both years (95 and 100%). However, ...