Author Archives: Lauri Munroe-Hultman

Nature returns: When dams come down, fish come back

This story was originally published on our new Medium blog platform

This year’s severe storms underscore the power of nature and the vulnerability of our coasts. While nature can destroy, it can also defend. Supported by federal funding for Hurricane Sandy recovery, we’re working with partners to restore and strengthen natural systems that provide not only habitat for wildlife, but also protection against rising seas and storm surge. This is the first in a series of stories highlighting results of our ongoing efforts to build a stronger coast.

“What did the fish say when it hit the wall? Dam!”

Whether you laughed or groaned, this joke captures the conundrum faced by migratory fish ever since European settlers harnessed the power of the Northeast’s rivers to make everything from flour to textiles to paper.

Migratory fish like alewife travel up rivers and streams to spawn. Credit: Chesapeake Bay Program/Will Parson

Fish like alewife and blueback herring (collectively called river herring), American shad, and American eel split their time between freshwater and saltwater habitats. They’ve been shut out of their spawning and nursery grounds in many waterways for centuries, whether by dams or other barriers. Bad news not only for them — river herring are under review for potential Endangered Species Act protection— but for big ocean species like cod and tuna who prey on them.

Following Hurricane Sandy in 2012, the U.S. Fish and Wildlife Service received more than $100 million to improve the health of coastal habitats to benefit wildlife and people. Since then, we’ve worked with partners to remove 12 dams and improve passage at two other sites, re-opening more than 100 miles of river to migratory fish.

With obstacles gone, the fish are returning to their old ways across the Northeast, often at the first opportunity.

Where West Britannia Dam once stood in Taunton, Mass., the Mill River is returning to its natural state. Credit: USFWS/Eric Derleth


In 2005, the rain-swollen Mill River threatened to breach Whittenton Pond Dam and flood downtown Taunton, a half-mile away. The incident made national headlines and spurred an effort to remove the river’s aging and unsafe dams, which kept migratory fish from reaching spawning grounds in Lake Sabbatia and its tributaries.

We worked with others to remove the dam in 2013 — and the river’s final barrier, West Britannia Dam, in January 2018.

Last spring, an underwater camera monitored by the Massachusetts Division of Marine Fisheries captured a river herring using the fish ladder at Lake Sabbatia — the first to enter the lake in 200 years. Before spawning season was done, at least 1,200 herring swam through.

A few sea lampreys passed through the ladder, probably the first to do so since the dams were built. Although lampreys are a problem in the Great Lakes watershed, where they are an invasive species that out-competes native fish, they are a boon to rivers and streams along the East Coast.

More than 1,300 young-of-the-year American eels made the journey to Lake Sabbatia, as well — more than any previous year. Eels reproduce in the ocean and mature in rivers and streams — the opposite of river herring, shad, and sea lampreys.

The nature-like fishway that replaced Bradford Dam allows fish and paddlers to pass. Credit: USFWS/Suzanne Paton

Connecticut/Rhode Island

The Pawcatuck River runs from Worden Pond in Rhode Island, west to the Connecticut border, and south into Little Narragansett Bay. Since 2010, we’ve worked with partners to remove four dams and update two fish ladders on the river.

White Rock Dam was taken down in 2015 and improvements were made to the fish ladder at Potter Hill Dam in 2016. Surveys in 2017 found river herring and shad above the White Rock site, which was once all but impassable. The fish count at Potter Hill was the highest in 15 years.

Last winter, Bradford Dam was replaced with a nature-like fishway, clearing nearly all of the river’s 34 miles to migratory fish.

Hyde Pond Dam held back Whitford Brook, a tributary of the Mystic River, for some 350 years before its removal in 2015. This year, more than 1,200 alewives were trapped upstream of the former dam.

Where Pond Lily Dam once held water, the banks of the West River now support plants. Credit: Connecticut Fund for the Environment/Save the Sound

In 2016, the dam blocking the West River on the Pond Lily Nature Preserve in New Haven, Conn., was taken down. The next spring, several alewives were seen above the former dam site. This year, 33 alewives were collected above the restored area.

Removal of Norton Mill Pond Dam in 2016 opened 17 miles of the Jeremy River to migratory fish. The following year, 127 sea lamprey nests were found above the former dam site; in 2018, there were 165.

New Jersey

In 2016, Hughesville Dam on the Musconetcong River was removed. A tributary of the Delaware River, “the Musky,” is a National Wild and Scenic River.

The next spring, the New Jersey Division of Fish and Wildlife confirmed an American shad upstream of the former dam site — possibly the first to make it that far since the dam was built in 1889.

Service biologist Katie Conrad holds an alewife during fish monitoring at Wreck Pond. Credit: USFWS

Wreck Pond was once connected to the ocean by a natural inlet that allowed fish to pass between the water bodies. After the inlet was replaced with a narrow pipe in the 1930s, the health of the pond deteriorated, and river herring struggled to enter the pond, the gateway to spawning grounds upstream.

Hurricane Sandy overwhelmed the existing entry to the pond, cutting a new inlet and flooding nearby homes. In 2016, partners installed a large box culvert next to the existing pipe to improve fish passage and reduce flooding.

In Fall 2017, young-of-the-year alewife on their way to the Atlantic were netted near the culvert — a clear sign that adults were making it to the spawning grounds upstream. This year, more than 150 were found — a 30-fold increase over any other year.

Perks for people, too

Removing barriers to fish benefits people, as well. A 2011 Service study found that every mile of river opened can contribute more than $500,000 annually in social and economic benefits once fish populations are at their full productivity.

Free-flowing rivers make the coast stronger in the face of future storms. They carry sediment downstream, where it nourishes coastal marshes and beaches that provide a natural defense to rising seas and storm surge. During Hurricane Sandy, coastal wetlands prevented $625 million in flood damages. In many cases, the risk of local flooding above a former dam is also reduced.

Canoeists enjoy the free-flowing Pawcatuck River. Credit: Wood-Pawcatuck Watershed Association

And then there’s the fun part — more opportunities for recreation like fishing and paddling. The American shad already returning to the Musky and Pawcatuck are prized by anglers for their feistiness. Experienced paddlers are able to “run” the nature-like fishways on the Pawcatuck instead of portaging around the old dams, making their passage almost as easy as that of migrating fish.

Stay tuned….

This is just the beginning. Three Sandy-funded dam removals happened last summer, and two new projects were funded this fall.

In the coming years, the National Fish and Wildlife Foundation will oversee nearly $3 million of ecological monitoring at nine sites where dams were removed. The work includes tracking fish with radio-telemetry as they move through waters once off-limits.

One thing is already clear, though — given a chance, rivers will rebound, fish will return, and people will benefit. That’s what we call a stronger coast.

A Sweet Solution to a Sticky Problem

When you’re a biologist at a site named for a legendary environmentalist, you feel a responsibility to do your job with the planet in mind.

Just ask Dr. Susan Adamowicz, Land Management Research and Demonstration Area biologist for the Northeast Region of the Fish and Wildlife Service. Stationed at Rachel Carson National Wildlife Refuge in Maine, she is tasked with finding innovative ways to manage wildlife habitat and takes inspiration from the renowned author.

In 1962’s Silent Spring, Carson, who also worked for the Service, sounded the alarm about pesticides that imperiled wildlife and people alike. She knew that many of the synthetic chemicals used to control unwanted plants and insects were dangerous to more than their targets.

For a healthy environment, Adamowicz seeks other solutions … and hopes she has found one with the help of a University of New Hampshire researcher.

A “Consummate Invasive Species”

Phragmites australis, or common reed, is an aggressive, nonnative marsh grass that pushes out native wetland plants. You’ve probably noticed its tall (up to 18 feet!), feathery, golden stalks in your neighborhood or along the freeway.

Phragmites is plentiful in the high salt marsh of the Great Marsh, the largest continuous stretch of salt marsh in New England. Three thousand acres of the 20,000-acre marsh in eastern Massachusetts lie within Parker River National Wildlife Refuge.

Phragmites changes the structure of the salt marsh, filling natural channels and tidal pools where waterbirds, fish, and invertebrates find food and safety. Many wildlife species find its dense patches impassable, and in the fall, when the stalks die back, stands of the plant turn to tinderboxes primed for wildfire, putting nearby homes and businesses at risk.

Biologists have long searched for effective ways to control Phragmites. It’s a determined adversary, however. Like those birthday candles that re-ignite, just when it seems defeated, it springs back to life.

According to Adamowicz, “Phragmites is the consummate invasive species. If you cut it or burn it, it comes back. If you can flood it for six months, that might kill it, but flooding is not always feasible.”

Phragmites grows along a marsh at Sachuest Point National Wildlife Refuge in Rhode Island. (Credit: Tom Sturm, USFWS)

While restoring natural tidal flow to coastal marshes is the preferred way to fight Phragmites,  replacing culverts, filling ditches, and improving drainage can take a long time. Treating it directly is necessary to keep it in check in the meantime.

Sadly, there’s been no good way to do that. Herbicides work in certain locations but pose a risk to native vegetation and groundwater — certainly not a solution Rachel Carson would embrace.

So Adamowicz teamed up with Dr. David Burdick, research associate professor and interim director of the Jackson Estuarine Laboratory at the University of New Hampshire, to explore innovative ways to control Phragmites. One of the methods they tested was sweet and simple.

Turning the Tables

Burdick had a hunch that sugar, the same kind you put in your coffee, might be Phragmites’ Kryptonite.

Dr. David Burdick takes notes at Parker River National Wildlife Refuge. (Credit: Gregg Moore, UNH)

Each summer, rising air temperatures and increased plant growth stimulate bacteria in salt marsh soils to convert organic matter and oxygen into carbon dioxide, water, and energy — a process called aerobic (“with air”) respiration. The activity quickly uses up soil oxygen, forcing other groups of bacteria to make energy using anaerobic (“without air”) respiration.

One by-product of anaerobic respiration is hydrogen sulfide gas, a potent toxin for plants as well as people. At typical levels, the gas is not deadly to most native plants, but it can be toxic to Phragmites.

Burdick thought increasing bacterial respiration, and therefore hydrogen sulfide levels, could kill the invasive.

“Because Phragmites is a master at getting oxygen to its roots for its own respiration, we could use this strength to kill it,” he mused. “By elevating soil hydrogen sulfide levels, we might stimulate the plant to oxidize the gas into a strong acid that it may not be able to tolerate.”

While he couldn’t control air temperatures, he could increase fuel for the bacteria — using glucose in the form of table sugar.

Pour Some Sugar on It

Burdick and his team first tested their idea in the greenhouse. They soaked Phragmites plants with bay water for three hours every two weeks to mimic the flooding that high-marsh plants get during the extra-high “spring” tides that come with the full and new moons each month.

Some plants (the control) received only the bay water; others got water with table sugar; still others water with extra salt; and the remaining, water with sugar and salt.

In the greenhouse study, plants receiving sugar or sugar-plus-salt (right, top and bottom) showed clear signs of distress within weeks of treatment. (Credit: Gregg Moore, UNH)

Both the sugar and sugar-and-salt treatments showed signs of stress within weeks and eventually died. Only the plants that received plain bay water or bay water with added salt lived.

The sugar-treated plants had very high soil acidity, possibly caused by sulfuric acid, the product of hydrogen sulfide oxidation. This supported Burdick’s theory.

Next, Burdick and Adamowicz headed to Parker River Refuge to set up a field study in the northern part of the Great Marsh. The research was supported by federal funds for Hurricane Sandy recovery and resilience projects.

Following the greenhouse trial, Burdick and his team tested the treatments in the Great Marsh at Parker River National Wildlife Refuge. (Credit: Gregg Moore, UNH)

They isolated individual Phragmites plants and applied the same treatments as in the greenhouse. Sugar and salt were put on the plants every two weeks, after the spring tides flooded the marsh.

The plants that got sugar had far greater mortality than the other treatments, even with uncontrollable environmental factors, such as rain — a clear sign that sugar is not sweet to Phragmites.

Refining the Technique

Adamowicz is pleased with the study results so far and eager to set up more field trials. She’s exploring ways to treat Phragmites with sugar and salt more efficiently and broadly, perhaps using a backpack sprayer to apply corn syrup at more-frequent intervals than every two weeks.

“This is another tool in our toolbox, and it’s nontoxic to wildlife, which is very desirable,” she said. “The more complicated response to Phragmites is ecosystem restoration, but in the meantime, we need a fast-acting tool to help native plants come back and buy time.”

If Rachel Carson were alive today, she would certainly approve of this environmentally sound method — and just might be thinking, “Sweet!”

Of Herring and Humans

(Credit: Chesapeake Bay Program)

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Update 4/19/18: For the first time in 200 years, a river herring has made it to Lake Sabbatia.

A river herring is captured by a remote camera at the Lake Sabbatia fish ladder in April 2018. Credit: MA Division of Marine Fisheries

If you’d been following the national news in October 2005, you might have heard about the Whittenton Dam crisis. After days of rain, the obsolete dam on the Mill River threatened to fail and flood homes and businesses in downtown Taunton, Mass.

Eventually, the rain stopped and the danger passed, but the crisis cost more than $1.5 million. The event highlighted the dangers of aging, unmaintained dams, and it spurred change.

“The near-failure of Whittenton Dam in 2005 really brought home the risk of aging dams for New Englanders,” notes Cathy Bozek, the U.S. Fish and Wildlife Service’s fish passage coordinator for the Northeast. “The event led to improved dam safety regulations in Massachusetts and, eventually, a funding source for removing or repairing dams in the state.”

In Taunton, the crisis energized a nascent effort to restore the Mill River by removing unsafe and obsolete dams, thus opening 30 miles of stream and 400 acres of lakes and ponds to migratory fish, including river herring.

Once so abundant their spring migrations turned rivers silver, herring populations had plummeted due to overfishing and dams that blocked the way to their spawning grounds. The decline affected myriad marine animals that prey on the species and prompted a statewide ban on harvesting river herring.

42-TNC Dam Removal Tauton_MG_5872

Construction workers excavate the site at West Britannia. (Credit: Lauren Owens Lambert)

In January 2018, the Service and its partners, including the Commonwealth of Massachusetts and The Nature Conservancy, removed the West Britannia Dam. The work was supported by funding for Hurricane Sandy recovery and resilience.

With the dam gone, river herring can now swim from Narragansett Bay all the way to their historical spawning grounds above Lake Sabbatia, and Taunton residents can breathe easy knowing that events like the Whittenton Dam crisis are in the past.

It’s a new day for humans and herring.

Read the whole story here.

Since 2009, the Service and partners have removed or replaced more than 507 barriers to fish passage from Maine to West Virginia, reconnecting more than 4,020 miles of rivers and streams and 19,300 acres of wetlands. While some of this work has been supported by federal funding for Hurricane Sandy recovery, partners across the Northeast have matched the Service’s contribution at nearly 5 to 1, contributing $56.1 million to the Service’s $12.5 million to restore aquatic connectivity for wildlife and protect communities.