The bank beside the spillway at Little River descends steeply enough that pond water pouring into a pool below the dam drowns out the sound of cars passing on the roadway. This time of year, bare branches above the pool are stationed with osprey scanning the roiling waters for signs of alewives that crowd too near the surface. In a flash, an osprey will leap from a branch, fold in its wide wings and plunge into the water, seizing on a seasonal traffic jam created decades ago by men.

Here and at dozens of rivers and streams across Long Island, dams and spillways erected for harvesting cranberries and ice, milling lumber and grain and other forgotten industries have impeded alewives and other fish from reaching historical freshwater spawning grounds, some for more than a century.

But conservationists have been working to undo those old restraints, collaborating with federal, state and local governments, academia and scientists, to build fish passages that bridge the historical dead-ends to freshwater spawning grounds. In doing so, they hope, the work will increase populations of fish vital to so much other wildlife, from osprey to whales. They may even give a boost to river otters now returning to these waters. 

River herring “are such a foundational part of the food chain,” said Emily Hall, conservation policy advocate at Seatuck Environmental Association, which has cataloged dams and coordinated work to undo them across the region. “If you increase these alewife populations, you’re basically going to be contributing to a tremendous chain of events for the entire ecological system.” 

Clearing the path

The annual migration of alewives up Little River, a tributary of the Peconic River, south of downtown Riverhead and across from the Suffolk County Center, is taking place as usual this year, but with a difference. By late May, if all goes as planned, the Woodhull Dam and its spillway that have held back the alewives for more than a century will be supplemented by a fish passage to allow river herring, as alewives are also called, to make their way to 95 acres of spawning grounds upriver without the aid of humans.

Another spillway started last year is already in place in Rockville Centre; a third is largely complete at the south end of Swan Lake in East Patchogue, where newly diverted water from the lake enters a curving passage that meets a canal under Montauk Highway.

Conservation groups and government agencies that make up the Long Island Diadromous Fish Work Group have already completed at least 10 fish passage projects around Long Island, said Victoria O’Neill, the state Department of Environmental Conservation’s Long Island Sound Study Habitat Restoration and Stewardship coordinator. But many more need to be addressed.

“Hundreds of relic dams can be found around Long Island on most freshwater tributaries,” she said. “Dam removal and fish passage construction allow fish to return to these native systems to spawn or live out the entirety of their lives.” 

The $1.2 million project at Little River has been a long time in coming, and one that has experienced delays tied to COVID-19 supply constraints and material price hikes — upward of 40%, says one official. No matter, say fisheries experts, like retired state biologist Byron Young, who have advocated for this passage for years — and in the interim done what they can to help propagate the species by cast-netting and hand hauling thousands of alewives over the dam each year, while measuring and classifying the fish for research. Young’s dedication to the alewife project at Little River is expected to be recognized with a resolution before the Suffolk Legislature next month to name that newest passage the Byron H. Young Fish Passage at Woodhull Dam. Work on the project could catch the end of the alewife spawning season, say people familiar with the project.

Islandwide effort

Completion of the project will mean that river herring and others, such as the American eel, will be able to make their way up an incline on their own, through a series of resting pools and into waters as far as a mile away, to Wildwood Lake.

It’s part of a bigger plan to open access to more than 300 acres of spawning ground across Long Island, undoing the effects of dams and spillways in waters from Rockville Centre to Southampton, allowing river herring to return to natural spawning grounds after decades of blocked access. Woodhull Dam, which includes a land bridge across Little River, was originally put in place to help those who harvested cranberries in nearby waterways.

Just a half mile upriver, a project completed more than a decade ago created a fish ladder on the Peconic at Grangebel Park, where biologists from the state DEC, The Peconic Estuary Partnership, Suffolk County Community College and Hofstra University have for years counted the spring passage of alewives using underwater cameras.

Tagging some of the fish has given researchers surprising new insights into alewives’ movements, including the finding that some fish travel frequently upriver and back out the ladder. It’s a discovery that has altered fish counts from upward of 60,000 alewives to a more realistic 20,000 in 2020, they say.

“We found there’s a fairly high rate of passage up and down the passage during the spawning season,” said Peter Daniel, a Hofstra professor who works with students to tag and monitor fish here and on other Long Island waterways. Tagging involves inserting a rice-size electronic transmitter in the fish to track its movements through the Grangebel Park passage, which is equipped with special antennas. Around 15% to 20% of the fish tagged and released in the previous year return through the ladder the following year, he said.

Two antennas allow the researchers to determine in which direction the fish are going. The fish stay as long as two months in the rivers, streams and spawning grounds, Daniel said. The work has led researchers to hypothesize that the river herring not only spawn here, but stay in the estuary, to feed as well. “We used to think that, like salmon, they didn’t eat, just spawned,” he said.

After spawning, laying 50,000 to 150,000 eggs each, adult alewives eventually move back out to the bay and the sea, as much as 100 miles out, by May’s end at the latest.

‘A good habitat’

The Peconic Estuary Partnership has been an important facilitator of the Woodhull Dam fish passage, which is being funded by grants from Suffolk County, the state DEC, the Town of Southampton and the U.S. Fish and Wildlife Service. But its biggest advocate has been Young, the retired DEC biologist who returned to the site on a recent day in March to discuss the importance of the work. Now 77, Young was quick to traverse the steep bank to net out a few alewives.

For more than a decade, he’s come here with his cast net and a ever-changing group of students to catch, measure and move upward of a thousand fish above the spillway they cannot traverse on their own. In the clear green water that spills out over the dam, some alewives can be seen attempting to jump the waters. Some may be those that have been hauled over by Young and his team. Others have a natural instinct to return here after hatching, going out to sea and returning to the freshwater of the river.

Suffolk County Community College Professor Kellie McCartin, whose dissertation was about the locally spawning alewives and their migration behavior, has involved her students in the counting and measuring of river herring. She estimates that some 22,000 fish swam through the Grangebel passage in 2021. “It shows there’s a really strong connectivity” to the spawning grounds, she said. “This is not really a barrier to activity.”

She and her students know that fish moved manually to the upper part of the Peconic River travel to spawning grounds to the south. “We’ve seen juveniles in Wildwood Lake. We know they are reproducing up there,” she said. “It’s good habitat. You can see they’re schooling in large numbers.” Juvenile alewives usually leave the lake and travel downriver and are out to sea by the fall, she said, usually by October.

The work of increasing spawning ground for alewives is important not just to increase local populations. McCartin said coastwide, alewives saw an overall decline last year, for reasons fisheries managers and biologists still haven’t figured out.

“These fish do extraordinary things and change behavior year to year,” she said. “We need to better understand them.”

Continuing work

Enrico Nardone, executive director of Seatuck Environmental, said while the work creating passages around human-made dams has been important, and a success in places that use more natural passages, work still needs to be done to study the success of other engineered fishways, like one a the Carmans River in Brookhaven.

“I think the jury is still out on whether it’s been successful from an ecological perspective,” he said of the metal-box structured fish ladders. “We’re trying to study it now,” because the number of fish moving through it “should be growing. It’s been there since 2008. We should see more fish coming back into the river.”

McCartin, whose dissertation included study of the passage at Carmans River, agreed. “We estimated extremely low percentages of alewives were using that ladder,” she said, “which is troubling. There needs to an alternative passage or no dam.”

Nothing, Nardone agreed, is as effective at helping the fish as complete dam removal. “We have to get past this legacy of dams,” he said.

Neighbors who live on the eastern side of Woodhull Dam welcome the work to increase fish passage, though not all are convinced it will work. One who lives at the edge of the land crossing, who would give his name only as Bob, said he believes there are barriers upriver, including another dam at Cranberry Bog, that could inhibit passage to Wildwood Lake. “They’re not going to make it,” he said

But Young, the retired DEC biologist, dismissed it, saying there are other streams and waterways that have allowed the fish to make it to the lake.

Kathleen Galvin, another neighbor, said the recent activity, with cranes, earth movers and giant pumps, has made the normally tranquil section of the river something of a nuisance in recent months, but she supports the work.

“It’s an eyesore,” she said. “I hope they put back the trees,” after work exposed new levels of light from the Riverhead County Center across the road. She’s lived here 20 years, she said, and has seen everything from turtles and snakes to fox and all manner of birds, most notably the osprey.