May 14, 2025 — If you have ever experienced an alewife migration, you know it is a true Maine experience that you must see to believe. As temperatures warm in Maine, alewives are beginning their remarkable migration into the Gulf of Maine. These small but mighty fish face new challenges as climate patterns shift.
“I love alewives, I think they are the most important fish in the sea and the river and the lake,” says Zach Whitener, Research Associate at the Gulf of Maine Research Institute. “When you see them scurrying up their brooks, they’ll swim on their side through half an inch of water. They are such determined to get where they want to go.”
Alewives join several species including blueback herring, American shad, and Atlantic salmon that migrate from ocean to freshwater. “These are anadromous fish, which means they live in the ocean as adults, but they spawn in freshwater,” Whitener explains. “In freshwater, the fish don’t have much competition as juveniles.”
After feeding in the ocean for three to four years, these fish return to their birthplace to spawn in the same lakes where they were hatched.
The Gulf of Maine serves as a “grocery store for most of the North Atlantic,” but climate change is creating complex challenges for migrating fish.