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The herring are running, all the more so as dams are razed

There’s solid evidence that our rivers are slowly becoming more usable for both fish and for people.

Ice clings to plants and rocks  along the gushing Herring Brook at the Herring Run on Barker Street in Pembroke.
Ice clings to plants and rocks along the gushing Herring Brook at the Herring Run on Barker Street in Pembroke.John Tlumacki/Globe Staff/file

If only this were a normal spring, fans of rivers and fish would have festivities galore to choose from: a celebration of Plymouth’s 400th anniversary and its Town Brook and herring, which sustained Natives and Pilgrims alike. Also, Earth Day’s 50th anniversary, World Fish Migration Day, and the annual herring-run celebrations that enliven so many New England towns.

Alas, it’s not a normal spring, not for humans, at least, with most events on hold. However, for river herring, there’s anticipation of a better spring, better, certainly, than in 2006, when herring counts reached a dismal low. For there’s solid evidence that our rivers are slowly becoming more usable for both fish and people.

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The age-old cry “the herring are running!” is all about how, as early as late March, millions of silvery alewives and bluebacks, collectively known as river herring, begin migrating from ocean depths to their coastal river, instinct pushing them upstream to the very pond they were born in, to spawn and raise young, before they return to sea late summer.

“It is an unending source of pleasure to watch them on their upward course,” a Cape Codder wrote in 1918. They “pass along like an invading army and nothing short of an impassable obstruction daunts them.”

But even by 1918, the fish’s upriver migration was badly blocked — by dams. Massachusetts today has over 3,000 dams, one of the earliest erected on Plymouth’s Town Brook in 1636 and most of the rest built in the 1800s and 1900s for powering riverside mills.

Relief for the fish came in 2006, when the state prohibited the harvest of river herring, and since then dam removals, new and repaired fish ladders, and other restoration efforts are further helping migratory fish to bounce back — in some rivers, from a trickle to a torrent.

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“What we’re seeing is that the count data is improving — that is, stabilizing or increasing, but not declining. So that’s good news,” said Bradford Chase, a biologist with the Massachusetts Division of Marine Fisheries. To be sure, there are far less river herring than there were 400 years ago. And they remain particularly vulnerable to habitat degradation, warming waters, and at-sea fishing.

During the herring count at the Upper Mill Pond ladder in Pembroke in 2013, herring gather after making their way to the top of the ladder.
During the herring count at the Upper Mill Pond ladder in Pembroke in 2013, herring gather after making their way to the top of the ladder. Debee Tlumacki for the Boston Globe/file

Yet, as obstacles fall away, the herring in some rivers are either reaching their ancestral spawning grounds for the first time in over 200 years, or at least ascending higher in their natal river than in a very long time. These upper reaches often provide them with more spawning and nursing habitat than when they were stuck in lower reaches.

For years, David Gould, who directs Plymouth’s Department of Environmental Affairs, was troubled by the backup of herring he witnessed every spring on Town Brook. The short river had seven dams, a near shutout for fish trying to reach the headwaters of Billington Sea.

“The only reason they were getting up there — we used to truck them up. It was pretty sad,” recounted Gould, who, 20 years ago, with the town’s blessing, and state and federal funds, began a major river overhaul. Six dams eventually came down, and today the fully restored river is a popular centerpiece for a thriving herring run and lovely park that attracts a variety of species, from kingfisher to otter to people.

While it’s difficult to spy fish “running” in deeper rivers, Town Brook’s shallower depths, its fish ladder and new eel ramp at historic Jenny Grist Mill make for excellent viewing.

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“Adults say, ‘Ick!’ when they see the eels, but kids are enthralled,” noted Gould.

At Mystic River, a long ancient fish passage that parallels Route 93 for a ways — some days, the fish are probably moving faster than the cars — the addition of a well-designed fish ladder between the upper and lower Mystic Lakes has made all the difference.

“The really cool thing is, we did this natural experiment and it worked. We allowed them to go past the dam for the first time in 150 years, and now they hop up the ladder and fly into the upper lake,” noted Andrew Hrycyna, a scientist with the Mystic River Watershed Association.

The Mystic once had so many herring, legend had it you could cross the river on their backs. With the upper habitat reopened to them, their numbers are exploding, up from 200,000 in 2012 to an estimated 780,000 last spring. In addition to the cool sight of them leaping up the new ladder, an underwater “fish cam” allows volunteers to participate in a virtual crowd-sourcing fish count from home. (A good activity for social distancing!)

The Mystic once had so many herring, legend had it you could cross the river on their backs.
The Mystic once had so many herring, legend had it you could cross the river on their backs. Patrick Herron

Herring Brook in Pembroke, Back River in Weymouth, Herring River in Harwich, the Monument in Bournedale, and the Nemasket in Middleborough. Migratory fish in these and other rivers are benefiting from large and small “tweaks” by the Division of Marine Fisheries and towns working in concert, said Chase, and from the “good-old-fashioned stewardship” of town herring wardens.

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The Oliver Mills Dam and its stunning park is a perfect place to picnic and also watch herring skipping up a natural rock fishway, on their run up the Nemasket. The river historically has been a “king” among herring runs, largely because its headwaters are composed of the state’s largest ponds, amounting to a colossal spawning ground. (These same ponds are the water supply for New Bedford and Taunton.)

On a chilly March day, Brendan Annett, who manages restoration projects for the Buzzards Bay Coalition, stood beside the Weweantic River in Wareham, where the Horseshoe Mill Dam was dismantled this winter, and talked about a growing trend. Since most dams no longer serve a purpose and are expensive to maintain, towns are opting to remove them and free up a river’s natural flow in the process.

Plans are afoot to turn the river and magnificent forest of white pine and red maple into a destination for hikers and kayakers. At the coalition’s first such project, the Acushnet Sawmill Reserve, completed in 2015, a dam’s removal led to rewilding a former polluted saw mill into a gem of a herring run with an easily observable fishway. Today it’s a magnet for birds and birdwatchers.

As for removing the dam on the Weweantic, “we thought a lot about how it could benefit many fish species,” said Annett — white perch, sea lamprey, American eel, and rainbow smelt, as well as herring. Also, the dam gone, the river can adapt to climate change “with saltmarsh grasses free to spread inland in response to rising sea levels.”

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“Rivers are long linear ecosystems, and dams chop them into tiny pieces and cause blockages, in just the way that cholesterol blocks the natural circulation of blood,” said Beth Lambert, director of the state’s Division of Ecological Restoration. The need for dam removal will grow, she believes, “as the magnitude and frequency of large storms increase and the structures continue to age.”

Ann Parson can be reached at parson-a@outlook.com.