According to the Maine Department of Marine Resources, an estimated 1,325 Atlantic salmon passed through the fishways at the Milford and Orono dams in 2022 on their way upstream. In 2021 only 561 salmon were counted, while 2020 saw 1,440 fish pass upstream.

Atlantic salmon have been protected under the federal Endangered Species Act since 2000. The Penobscot once hosted an estimated 100,000 wild salmon before dams, logging, and pollution nearly extirpated the species from the river.

The numbers of river herring moving upstream in the Penobscot also increased in 2022. DMR estimates that 2,052,837 blueback herring and alewives passed through the dams at Milford and Orono—an increase of approximately 300,000 fish over 2021 and the most since the department started counting them in 2014.