Climate Chronicles: Is the herrings run spring's true starting line?

Each spring along Maine’s rivers, shimmering schools of herring surge upstream. For many locals, that annual run feels like the real beginning of the season.

Today’s Climate Chronicles question comes from Brian:

Locals often recognize the herring migration as an unofficial sign of spring, why is that, and is there any truth to it?

Let’s first discuss how herrings migrate.

What are herring runs? (WGME)

Herring—a broad term that includes alewives and blueback herring, are born in freshwater but spend most of their lives growing in the ocean.

Each spring, they migrate from saltwater back into rivers and lakes to spawn.

This migration typically occurs between May 15 and June 15 in Maine, depending on water temperatures and river flow, but can begin as early as April in southern New England.

Herring migration is an important part of our ecosystem, providing food to Osprey and Bald Eagles this time of year.

Maine Herring Runs (WGME).

Herring runs can be found all along Maine’s coastline, in rivers connected to freshwater ponds and lakes.

There are also many observation sites along these streams, where Mainers can watch herring make their way through fish ladders.

For a list of events in Maine and New England, click here.

Fish ladders are installed along many herring runs where dams or natural drops would otherwise block their path upstream.

These structures create a series of small steps or pools, allowing the fish to gradually work their way past obstacles and continue toward their spawning grounds.

Herring travel in large, tightly packed schools, so when they reach these ladders, they often bunch together, creating an impressive, almost nonstop stream of fish pushing upstream.

Is herring migration the unofficial start to spring? (WMGE)

But is herring migration the unofficial start to spring?

It depends on what you look at. In many ways, yes. Herring migration lines up with several classic signs of spring.

Herring begin their migration once ice clears from inland waters, allowing rivers and streams to flow more freely with snowmelt.

They also rely on water temperature. When ocean temperatures climb into the mid-40s, it signals that it’s time to begin their run upstream.

Other classic signs of spring (WGME).

All in all, there is truth to herring migration being an unofficial start to spring.

Other classic signs of the season include nature waking up, early shoots and blooms emerging, and trees beginning to bud.

Wildlife returning is another big signal, from birds becoming more active to the sound of spring peepers filling the night.

All are classic signs of spring ramping up, which includes herring runs.