February 10, 2023 — Restoration of the critically endangered Atlantic salmon is an important issue in the rivers of Maine. Dams on Maine rivers have long been known to impact fish populations, but a new study led by the University of Maine quantifying the time and energy lost by Atlantic salmon stopped by dams indicate that the structures might have even more of an impact than once thought.
Atlantic salmon return to the rivers of Maine from the ocean every spring to make the long, arduous swim upstream to spawn in freshwater. When the fish are stopped by dams, they are stuck in warmer waters for longer than expected, which can deplete the fat they have stored up to power their journey. The stored energy isn’t just used for migration, but also producing gametes, developing secondary sexual traits and spawning.
“Salmon limit the food they eat in freshwater, so excess energy lost during their migration doesn’t get replaced,” says Sarah Rubenstein, who completed her masters of science in wildlife ecology at the University of Maine in 2021. “However, spawning takes a lot of energy, so the more energy reserves salmon have left after migrating and during spawning, the more likely they will be at successfully reproducing. This is particularly important here in Maine where Atlantic salmon populations have been on the decline since the 1800s.”