Fish ladders across Long Island aim to aid alewives during spawning season
Alewives pool at the bottom of the construction site of a fish ladder through Woodhull Dam on the Little River in Riverhead in March 2022. Credit: Newsday/Steve Pfost
The alewife spawning season that begins this month across Long Island will be helped by several fish passages constructed over the past two years to provide the feeder fish access to spawning waters long barred by manmade dams.
Early results are in from one the newest so-called fish ladders installed just south of the Peconic River near Riverhead, and while encouraging, they are far below expectations, biologists said.
Alewife, also known as river herring, are a vital food source for fish, birds and mammals in Long Island waterways, where they traverse from saltwater ocean and bays to local creeks and rivers to spawn in freshwater lakes and ponds. They are a food source for everything from predator finfish to ospreys and whales, but they are off limits to local fishers.
After female alewives lay 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. Their offspring follow as juveniles in the fall.
The past decade has seen considerable efforts made across the Island to provide spawning alewives with new access to waterways that had been outside the fishes’ reach. These fish ladders, some costing more than $1 million, have been put in place from Rockville Centre to the East End in the past five years.
One closely watched passage is on a section of the Little River in Riverside just south of downtown Riverhead, where conservationist groups and government led the building of a fish passage completed in 2023 that allows river herring to swim up a stainless steel chute beside the Woodhull Dam.
The $1.2 million project allows the fish to make their way from the Peconic River in Riverhead, where there is another successful ladder at Grangebel Park, before reaching the Byron H. Young Fish Passage at Little River. There, those that make it across can spawn as far away as Wildwood Lake about a mile to the south, after more than a century of being prevented by the Woodhull Dam.
Last year was the first full year of that new fish ladder’s operation, and the results, logged by cameras reviewed by Suffolk County Community College biologists, indicated a slow start.
Camera data from 2024 showed that of the upward of 40,000 alewives that gathered in a roiling pool at the base of the dam, only 983 river herring made it through the fish ladder, according to Kellie McCartin, professor of marine biology at Suffolk County Community College.
"Ideally we would love more fish to go over," she said, "but considering last year was the first year, I’m very optimistic we’ll get a higher percentage coming across this year."
One of the ways to do that is to adjust the flow dynamics of water passing through the ladder.
"It was the first season and it's always a little trial-and-error to get fish to do something new," said Joyce Novak, executive director of the Peconic Estuary Partnership, which administered the program with funding from local, county, state and federal funds. "We're hopeful it will be better this year with some of the alterations they've made."
In comparison with the steel fish ladder in Riverside, a "nature-like" fish ladder created at Swan Lake in East Patchogue, also installed in 2022-23, uses stones in a creek-like eddy off the lake to encourage fish to cross over into spawning grounds. "Nature-like ladders do much better," said McCartin. Data for the Swan Lake passage wasn't available.
Nature-like fish ladders can’t always be built, given the dynamics of Little River and the pond that feeds it. The Riverside fish ladder is named for Byron Young, a retired state biologist who for years led an effort to physically transport the spawning alewives from the river to the pond, while measuring and counting them for research.
McCartin said the completion of the Byron Young ladder leaves only one other place along the Peconic River where alewives are prevented by dams from spawning — a site in Upper Mills Pond on the Peconic River in Rivherhead. There’s a plan awaiting approval to upgrade it, removing all manmade impediments on that river. Novak said the $2.2 million-plus proposal is "shovel ready," and she hopes state bond-act money can pay for the project, which is in a challenging location because of power lines in the area.
Peter Daniel, a Hofstra University professor who oversees a program to monitor tagged alewives through local waterways, said none of the fish tagged in his program came up the new ladder at the Woodhull Dam. Daniel's program uses special antenna that pick up the presence of tagged fish inside the ladder.
"We didn’t really have any tagged fish make it up the ladder," he said. One that made it partly up wound up going back down, he said. In 2023, 90 fish tagged as part of the program were identified in the pool below the dam, so Daniel knows fish want to make their way up to spawn.
Daniel said his researchers tried numerous ways to adjust the flow of the river through the ladder to make it suitable for the fish, "but it didn’t seem to have any effect."
Daniel said his group had not yet reviewed results of the new nature-like passage at Swan Lake, or one in Rockville Centre, but the results from the Grangebel Park ladder in Riverhead are clear. "Over 90% of the fish that attempt that ladder get up," he said.
A nature-like ladder had been contemplated for the Woodhull Dam site, Daniel noted, but "there were some physical constraints to the area that make it very difficult to produce a fish ladder. It’s a very narrow area of land. It just wasn’t feasible for a nature-like ladder."
The alewife spawning season that begins this month across Long Island will be helped by several fish passages constructed over the past two years to provide the feeder fish access to spawning waters long barred by manmade dams.
Early results are in from one the newest so-called fish ladders installed just south of the Peconic River near Riverhead, and while encouraging, they are far below expectations, biologists said.
Alewife, also known as river herring, are a vital food source for fish, birds and mammals in Long Island waterways, where they traverse from saltwater ocean and bays to local creeks and rivers to spawn in freshwater lakes and ponds. They are a food source for everything from predator finfish to ospreys and whales, but they are off limits to local fishers.
After female alewives lay 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. Their offspring follow as juveniles in the fall.
The past decade has seen considerable efforts made across the Island to provide spawning alewives with new access to waterways that had been outside the fishes’ reach. These fish ladders, some costing more than $1 million, have been put in place from Rockville Centre to the East End in the past five years.
One closely watched passage is on a section of the Little River in Riverside just south of downtown Riverhead, where conservationist groups and government led the building of a fish passage completed in 2023 that allows river herring to swim up a stainless steel chute beside the Woodhull Dam.
The $1.2 million project allows the fish to make their way from the Peconic River in Riverhead, where there is another successful ladder at Grangebel Park, before reaching the Byron H. Young Fish Passage at Little River. There, those that make it across can spawn as far away as Wildwood Lake about a mile to the south, after more than a century of being prevented by the Woodhull Dam.
Last year was the first full year of that new fish ladder’s operation, and the results, logged by cameras reviewed by Suffolk County Community College biologists, indicated a slow start.
Camera data from 2024 showed that of the upward of 40,000 alewives that gathered in a roiling pool at the base of the dam, only 983 river herring made it through the fish ladder, according to Kellie McCartin, professor of marine biology at Suffolk County Community College.
"Ideally we would love more fish to go over," she said, "but considering last year was the first year, I’m very optimistic we’ll get a higher percentage coming across this year."
One of the ways to do that is to adjust the flow dynamics of water passing through the ladder.
"It was the first season and it's always a little trial-and-error to get fish to do something new," said Joyce Novak, executive director of the Peconic Estuary Partnership, which administered the program with funding from local, county, state and federal funds. "We're hopeful it will be better this year with some of the alterations they've made."
In comparison with the steel fish ladder in Riverside, a "nature-like" fish ladder created at Swan Lake in East Patchogue, also installed in 2022-23, uses stones in a creek-like eddy off the lake to encourage fish to cross over into spawning grounds. "Nature-like ladders do much better," said McCartin. Data for the Swan Lake passage wasn't available.
Nature-like fish ladders can’t always be built, given the dynamics of Little River and the pond that feeds it. The Riverside fish ladder is named for Byron Young, a retired state biologist who for years led an effort to physically transport the spawning alewives from the river to the pond, while measuring and counting them for research.
McCartin said the completion of the Byron Young ladder leaves only one other place along the Peconic River where alewives are prevented by dams from spawning — a site in Upper Mills Pond on the Peconic River in Rivherhead. There’s a plan awaiting approval to upgrade it, removing all manmade impediments on that river. Novak said the $2.2 million-plus proposal is "shovel ready," and she hopes state bond-act money can pay for the project, which is in a challenging location because of power lines in the area.
Peter Daniel, a Hofstra University professor who oversees a program to monitor tagged alewives through local waterways, said none of the fish tagged in his program came up the new ladder at the Woodhull Dam. Daniel's program uses special antenna that pick up the presence of tagged fish inside the ladder.
"We didn’t really have any tagged fish make it up the ladder," he said. One that made it partly up wound up going back down, he said. In 2023, 90 fish tagged as part of the program were identified in the pool below the dam, so Daniel knows fish want to make their way up to spawn.
Daniel said his researchers tried numerous ways to adjust the flow of the river through the ladder to make it suitable for the fish, "but it didn’t seem to have any effect."
Daniel said his group had not yet reviewed results of the new nature-like passage at Swan Lake, or one in Rockville Centre, but the results from the Grangebel Park ladder in Riverhead are clear. "Over 90% of the fish that attempt that ladder get up," he said.
A nature-like ladder had been contemplated for the Woodhull Dam site, Daniel noted, but "there were some physical constraints to the area that make it very difficult to produce a fish ladder. It’s a very narrow area of land. It just wasn’t feasible for a nature-like ladder."
Mark Harrington, a Newsday reporter since 1999, covers energy, wineries, Indian affairs and fisheries.
NewsdayTV celebrates Women's History Month From a civil rights pioneer to history being made at the SCPD, NewsdayTV is celebrating Women's History Month with a look at changemakers and trailblazers with ties to LI.
NewsdayTV celebrates Women's History Month From a civil rights pioneer to history being made at the SCPD, NewsdayTV is celebrating Women's History Month with a look at changemakers and trailblazers with ties to LI.