Hydroelectric power plants and the dams they place on rivers often threaten the survival of fish that live in the ocean but spawn in fresh water.
With the help of a unique setup on the Mohawk River, however, the New York Power Authority’s Crescent Hydroelectric Project is making strides toward protecting river herring, an important species that serves as food for bigger fish, including cod, that feed millions of people.
The authority recently sent a study to federal regulators detailing the success of an underwater sound system that scares herring away from the plant’s intake, leading to fewer fish being chewed up in the turbines that generate electricity.
Herring and alewife, collectively referred to as river herring, as well as salmon, smelt, shad, striped bass and sturgeon, are anadromous fish — fish that are born in fresh water, spend their lives in the ocean and return to fresh water to spawn. Their young grow in freshwater rivers, such as the Hudson and Mohawk, and then swim to the Atlantic Ocean to live out most of their lives.
Concerns over the health of herring are growing as quickly as their numbers are depleting, and there have been calls to protect them as endangered species. Some environmentalists, aware of the loss of spawning grounds due to dams on rivers, are calling for dams to be torn down.
A unique success
The Mohawk River is different. Here, the man-made structures actually provided a way for fish to get upstream.
Until 1918, when the latest version of the Erie Canal was opened, anadromous fish couldn’t get past the majestic Cohoes Falls. But the canal system’s flight of locks in Waterford sidesteps the 75-foot-high, 1,000-foot-wide falls, and herring started catching on not long after the bigger canal opened on the river.
Today, herring make an annual run up the Mohawk River through the locks, getting as far as Herkimer County. They’re now spawning on a freshwater river system they couldn’t access before the river was turned into a canal.
In recent years, declining populations of blueback herring forced a halt to fishing in Connecticut, North Carolina, Massachusetts and Virginia, and scientists have been studying various impacts on their survival for years.
The Atlantic States Marine Fisheries Commission four years ago ordered states along the Eastern Seaboard to monitor their populations, and scientists believe pollution, the lack of adequate spawning territory and accidental catch by commercial fishing operations are responsible for the rapid decline in their numbers — from 75 million pounds of herring taken by commercial fishermen in 1957 to less than 2 million in 2010.
Nearly 10,000 kilowatts of energy is created from the power of the Mohawk River’s flow into the NYPA’s Crescent hydroelectric plant’s turbines on the river between Albany and Saratoga counties. It’s the final power plant on the Mohawk before it meets the Hudson River, about 10 miles downstream of the authority’s Vischer Ferry hydroelectric plant opposite Lock 7 in Niskayuna.
Both were built in 1925 with two turbines and were expanded to hold four turbines each by 1993.
The NYPA began testing sound-based methods of scaring fish away from the intake at its Fitzpatrick nuclear power plant on Lake Ontario in the late 1980s.
In 2007, the Federal Energy Regulatory Commission, which granted a license to operate the Crescent hydroelectric project, ordered the authority to install a sound system on the river to help young blueback herring avoid the power plant’s turbines. Both the state Department of Environmental Conservation and U.S. Fish and Wildlife Service named blueback herring as species in need of protection.
The results were lackluster, according to NYPA meeting minutes, suggesting “the system may need to be adjusted to more effectively inhibit [juvenile blueback herring] from approaching” the project.
Flood had stalled effort
Efforts to improve the system and report to regulators had been stalled by flooding since 2010. But the work resumed and a report issued to the FERC this summer shows changes in the sound system have improved the migration of the young fish — keeping them out of the turbines and sending them towards the only passage down to the Hudson River — the state Canal Corp.’s flight of locks that meet the Hudson River in Waterford.
Normandeau Associates Inc., of Portsmouth, N.H., won contracts totaling about $850,000 to work on the project over the past six years, and the most recent results show re-aiming the sound system was beneficial. Scientists from the New Hampshire company targeted the prime time when the baby fish head to the sea — September and October — and found broadband sound projection, when aimed appropriately, saves fish.
The system, which uses waterproof speakers to blare sound underwater, was also deployed from May to July to help the blueback herring return to the sea after spawning.
Including engineering and permitting, the entire project cost about $2 million, according to information provided via email by NYPA spokeswomen Connie Cullen and Maura Balaban.
A similar sound system is also scaring fish away from the intake of the Vischer Ferry hydroelectric plant upstream, according to the authority-.
According to Normandeau’s report, a copy of which NYPA shared with The Daily Gazette, more than three-quarters of the young blueback herring made it past the power plant’s intake channel during 2012 testing.
76% survive gantlet
Scientists determined the numbers by measuring the amount of fish upstream of the power plant and the numbers downstream, and 76 percent of the fish spotted upstream of the plant made it through.
“This was significantly higher than expected,” scientists wrote in the report. “These results demonstrate significantly improved downstream passage at Crescent for the majority of out-migrating juvenile blueback herring.”
The authority has been working with industry organizations on developing and testing such systems, producing numerous scientific journal studies on the subject, according to the NYPA.
Federal and state regulations require state-chartered energy suppliers to pay attention to their impact on the environment.
“NYPA takes its role as environmental steward very seriously and recognizes it has a duty to minimize the potential impact of its operations on air, water, land, fish and wildlife,” Balaban said.
DEC Region 4 spokesman Rick Georgeson said in an email that the agency is “working with all hydro facilities, from Green Island to Little Falls, as part of their license requirements to determine the best way to safely pass herring through their projects, as they spawn and then migrate back to the ocean.”
Dam removals elsewhere
Researcher Karin E. Limburg said scientists with concerns about human impacts on the environment are calling for dams to be torn down. A professor at the SUNY College of Environmental Science and Forestry in Syracuse, Limburg has been studying herring migration for more than a decade.
In a study published in August in the scientific journal “Evolutionary Applications,” Limburg and others determined many systems aimed at helping fish get past power plants simply fail.
“We made a call for taking down dams,” Limburg said. “You can’t always assume that all dams are going to work or all fish passages are going to work. We showed how terribly performing dams are on three of the largest rivers in the East,” Limburg said.
She points to the success of tearing down the Edwards Dam on the Kennebec River in Maine in 1999. In that case, environmentalists purchased the dam and found other spots for electrical production, she said.
The dam blocked the lowest point of the river for more than a century, preventing salmon, shad, river herring and striped bass from getting upriver to spawn. When the dam came down, it opened up roughly 18 miles of river upstream, Limburg said.
Not long after it came down, Limburg said roughly 2 million alewife herring swam upstream.
“We look at that as an example of the possible,” she said.
For Limburg, the situation at the Crescent Hydroelectric Facility and the Mohawk River’s Erie Canal system are unusual in allowing fish to spawn and serving as a replacement for the hundreds of miles of rivers and streams cut off by dams.
The Mohawk, Limburg said, can be seen as one of few new refuges river herring can make use of as an alternative.
“I see them as exploiting a newly accessible place,” Limburg said.
Even with the locks, it’s unlikely herring didn’t make it back to the ocean this year: freshly fertilized eggs sitting on the river’s bottom don’t do well during situations like the deadly flash flooding that inundated the Montgomery County village of Fort Plain this year.
“The adults would’ve come in and gone out, but babies and eggs don’t handle high flow terribly well,” Limburg said.
According to the FERC, NYPA’s work to protect the herring isn’t finished. The U.S. Fish and Wildlife Service is calling for meetings with NYPA to talk about two additional ways of helping the fish.
One is getting an early warning system that can automatically open up the pathways atop the Crescent facility’s dams to let fish make it over the dam. The agency also wants to discuss reducing power generation when possible to maximize the number of fish making it through during their migration.