Date of Award


Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)




Michael T. Kinnison

Second Committee Member

Joseph Zydlewski

Third Committee Member

John F. Kocik


Acoustic telemetry was used to evaluate passage success, survival and behavior of migrating Atlantic salmon (Salmo salar), at both the smolt and adult stages, through the Penobscot River and Estuary, Maine. Survival and behavior of migrating hatchery (n=493) and naturally-reared (n=133) smolts were evaluated in 2005 and 2006. Mortality, movement rates, and use of a secondary migration path (the Stillwater Branch) were quantified, and related to rearing, release history, and migratory condition (gill Na+,K+-ATPase activity and condition factor). River sections containing three mainstem dams (Howland, Milford and West Enfield dams) accounted for 43% and 60% of total losses for 2005 and 2006, respectively, though these sections accounted for only 16% and 6% of monitored reaches. Survivorships through individual sections with dams ranged from 95-100% and 71-100% in 2005 and 2006, respectively. Movement rates were significantly slower at dams compared to free-flowing reaches, and smolts arriving at dams during the day experienced longer delays than smolts arriving at night. Hatchery smolts released in April were not ready to migrate at time of release, but migrated earlier than wild smolts in both years. Gill Na+,K+-ATPase activity was positively associated with movement rate to the estuary in both years. Further, gill Na+,K+-ATPase activity for wild smolts was similar to hatchery smolts that were released 29-26 days earlier in 2005 and 2006, respectively. Hatchery smolts released in May showed similar freshwater survival compared to both wild smolts and hatchery smolts released in April, but behavior was more similar to wild smolts than earlier-released hatchery smolts. Use of the Stillwater Branch by individual release groups ranged from 0-26% and 0-19% in 2005 and 2006, respectively, and was positively related to discharge. Smolts released in the Pleasant River at Milo used the Stillwater Branch at a significantly lower rate than smolts released in the mainstem. These results indicate that fundamental differences exist between hatchery and naturally reared smolts, and may help mangers determine which rearing and release protocols best meet the goals of the restoration program. Acoustic telemetry was used to quantify riverine behavior and passage success for pre-spawn adult Atlantic salmon in the lower Penobscot River, Maine in 2005 (N=10) and 2006 (N=25). Passage success was extremely poor in both years. Only 38% (3/8) and 8% (2/25) of tagged salmon successfully passed the fourth upstream dam in 2005 and 2006, respectively. In 2005 and 2006, 100% (3/3) and 74% (17/23) of unsuccessful migrants fell back into the estuary and few successfully re-ascended. Water temperature in the mainstem exceeded 27°C in both years, and fallback behavior was common when temperatures exceeded 22°C. A small stream provided thermal refuge during morning hours only and was warmer than the mainstem during afternoon hours. Results from this pre-removal assessment indicate that insufficient upstream passage at dams in the lower Penobscot River can severely limit migratory success in this system. As part of the Penobscot River Restoration Project (PRRP), the planned removal of two dams (Great Works and Veazie dams) is expected to enhance passage through the mainstem corridor for salmon and other migratory fish. Results from this study suggest that removal of these lower river dams will improve migratory success for adult salmon. However, this study highlights the need to improve downstream passage for smolts at dams that will remain in place (Milford, Howland and West Enfield dams).