Maine river herring run tops 20 million, highest in decades

When Maine’s rivers swell each spring, a stunning silver surge returns to waterways that had been largely silent for generations. This year’s count — roughly 20 million river herring, commonly called alewives — marks a dramatic rebound that scientists, fishermen and tribal nations say is the result of long-term habitat work and changing fisheries management.

The comeback has drawn attention not only for its scale but for what it signals about restoring coastal rivers: where dams come down and fishways are built, nature can respond fast. The rebound on rivers like the Penobscot has become a focal point for conservationists and local communities celebrating an ecological revival and renewed cultural ties to a once-ubiquitous food source.

What triggered the rebound: dams, moratoriums and restoration projects

For centuries, millions of alewives ran from the Atlantic into Maine’s rivers to spawn, feeding people, wildlife and farmlands. But as rivers were dammed from the 18th century onward and commercial offshore harvesting intensified, populations plunged. By the late 20th century, inland catches had dropped from an average of about 3 million pounds to roughly 150,000 pounds annually.

A coordinated recovery began in the late 1990s. Key actions included:

• Large-scale dam removals and bypass construction to reopen historic spawning habitat.
• A federal and state moratorium on commercial offshore alewife fishing, implemented in the early 2010s, which reduced pressure on returning adults.
• Local restoration projects and community-led fish passage efforts, such as building fish ladders and channels around remaining barriers.

Those efforts accelerated through the 2000s and 2010s. Major river projects completed by 2016 unlocked miles of upstream habitat; combined with the fishing moratorium, they set the stage for the population surge now being documented.

Penobscot River: a case study in rapid recovery

The Penobscot River has emerged as a flagship example of what coordinated restoration can achieve. Removing two significant dams there has reopened long-blocked reaches, and biologists describe the resulting alewife run as one of the most impressive recoveries in recent memory.

Why the Penobscot matters

• It reconnects spawning and nursery habitat for multiple migratory species, including alewives and Atlantic salmon.
• Large adult returns create immediate ecological benefits for predators and nutrient cycles.
• The project demonstrates how public-private partnerships and long-term planning can deliver measurable conservation outcomes.

Rustin Taylor, executive director of the Alewife Harvesters of Maine, told Inside Climate News that some river systems have gone from near-total loss of fish runs to hosting what could be among the largest populations on the planet. That kind of turnaround underscores why river reconnection is being watched nationally.

Ecological and cultural ripples of the alewife return

Alewives are more than a local seafood commodity. They act as a nutrient conveyor, hauling ocean-derived energy upriver when they spawn, then transferring those nutrients into forest and freshwater food webs through predation and decomposition. The effect multiplies across species:

• Bears, otters, eagles and other predators feed on the runs.
• Forest soils benefit when nutrients move from fish into terrestrial systems.
• Smaller fish and invertebrates gain from increased food availability at multiple life stages.

For Indigenous communities, the return of river herring carries cultural meaning as well. The Passamaquoddy name for the species, siqonomeq, is often translated as “the fish that feeds all,” reflecting generations of reliance on these runs.

Numbers and milestones: how the recovery unfolded

The recovery timeline includes several turning points:

1. 18th–19th centuries: widespread dam construction reduces access to spawning grounds; coastal fisheries expand.
2. By 1994: dramatic declines recorded — inland landings fall to roughly 150,000 pounds.
3. 1999–2016: intensive river restoration and dam removal projects undertaken in Maine.
4. Early 2010s: moratoriums and stricter fisheries management reduce offshore pressure on alewives.
5. 2025: monitoring teams tally about 20 million alewives moving up Maine rivers.

These figures come from a combination of state counts, tribal monitoring and conservation organizations tracking runs at key weirs and counting stations. The increase is not uniform across all watersheds, but where barriers have been removed or fishways added, returns have been particularly strong.

How communities and managers are adapting to the comeback

With alewives returning in large numbers, communities are adjusting both culturally and economically. Traditional alewife festivals — once muted by scarce runs — are reviving as celebrations and educational opportunities. At the same time, managers are balancing restoration success with sustainable harvest planning and continued habitat protection.

Actions now underway or being considered include:

• Improved monitoring programs to track run size and spawning success.
• Targeted fishway projects for rivers that still have partial barriers.
• Community-based harvest rules that respect tribal and local practices while ensuring long-term population health.

Remaining challenges and why momentum matters

Even with recent gains, challenges remain. Some rivers still have dams without passage solutions, and offshore ecosystems face pressures from warming seas and changing prey dynamics. Continued investment in river reconnection, science-based fisheries management and habitat protection will be critical to sustaining the rebound.

Nevertheless, marine and freshwater managers point to the alewife story as evidence that thoughtful restoration can deliver rapid, measurable returns for wildlife, local economies and cultural traditions — when communities, tribes, and agencies work together.

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Michael Thompson

Michael Thompson is an experienced journalist covering U.S. and global news. With ten years on the front lines, he breaks down political and economic stories that matter. His precise writing and keen attention to detail help you grasp the real‑world impact of every event.