Tagging the humble herring on the Pawcatuck River
The Providence Journal
By Alex Kuffner
Journal Staff Writer
Posted Apr 24, 2018 at 9:15 PM
Updated Apr 24, 2018 at 10:46 PM
Researchers begin to track the fish to measure the success of decades-long project to clear a path to spawning grounds in Worden Pond
HOPKINTON, R.I. — Annie Ragan pried open the mouth of an alewife herring and used a notched tube to insert a radio transmitter down its gullet.
The University of Rhode Island graduate student eased the pea-sized device into the fish’s stomach and gave a gentle tug on the thin wire antenna protruding from its mouth like an errant strand of hair. It was lodged in place and wouldn’t be going anywhere.
The process, which took just a few seconds to complete, didn’t look pleasant for the little, silvery fish, but it’s a tried-and-true tagging technique that shouldn’t interfere with feeding or otherwise cause the creature harm.
“We haven’t had anyone regurgitate it yet,” said Suzanne Paton, senior biologist with the U.S. Fish and Wildlife Service.
That’s a good thing because the transmitters will help determine whether decades of work and millions of dollars spent to restore fish passage along the Pawcatuck River have succeeded in opening up the 34-mile-long waterway to spawning alewife and blueback herring, as well as shad and trout, all species that play a critical role in the natural world.
The hope is that, after the removal of three of the river’s major dams and the construction or improvement of fish ladders on the three others, migrating fish will be able to swim up the full length of the river from its mouth at Little Narragansett Bay in Westerly to historical spawning grounds in Worden Pond in South Kingstown.
The final piece of the puzzle was completed this past winter after the Bradford Dam was taken down and replaced by a new fish-friendly riverbed made up of rows of boulders that slow the current down to ease passage upstream.
The migration that just got underway over the past few weeks is the first one in more than a century in which fish should have unfettered access to the entire river. Paton and the other members of the research team from URI, the state Department of Environmental Management and the U.S. Geological Survey will be tracking them along the way.
“The main question is whether they get all the way up the river so they’re reaching the ideal habitat,” she said. “Hopefully, they just cruise right up to Worden Pond.”
But for some fish that were trying to get past Potter Hill Dam in Ashaway on Monday morning it wouldn’t be such an easy cruise. They would go on a detour.
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The waters were thick with alewife, the only species migrating this early in the year. After making it through a gauntlet of cormorants and seagulls that were dive-bombing the churning waters below the dam, the fish were met by the researchers.
Waiting above the resting pool set in a turn in the dam’s fish ladder, they scooped out netfuls of fish and transferred them to an oxygenated holding tank.
One by one, they checked the sex of each fish and then measured it. Then they inserted one of two types of transmitter.
The majority got PIT tags, passive integrated transponders, that were not much bigger than a grain of rice and were slipped into a small incision on their bellies. PIT tags can last years, providing information on a fish’s movements over many spawning seasons, but they have a weak signal and can only transfer data when a fish swims within a few feet of an antenna fixed in place.
A smaller group got more expensive radio transmitters that have enough power for only a few months but will send out a strong signal that can be picked up over greater distances. If a fish goes missing, the researchers can go out in a boat with a hand-held antenna to find it and pinpoint its position.
The team worked fast to get the radio tags in place. URI graduate student Seaver Anderson dabbed glycerine on a transmitter to help it slide down the fish’s esophagus. Doctorate student Emma Lundberg held the fish firmly against a measuring board and Ragan slipped the transmitter in with a practiced hand.
“The less time out of the water, the better,” Anderson said.
Most of the fish were dumped back in the river above the dam, swimming on as their instinct demanded. But, to ensure the study has data from all parts of the river, some were trucked upstream while the less fortunate were taken all the way back down the river to see how well they navigate through its lowest reaches.
“They drew the short straw,” Paton said of the latter group.
In all, the researchers will tag 200 river herring this year and 100 shad, which are expected to start migrating in May. They will tag the same numbers next year as well.
The $300,000 study is being funded entirely through federal money allocated after superstorm Sandy in 2012, which caused extensive flooding throughout the Pawcatuck watershed. The recovery funds were also used to take down the White Rock Dam and the Bradford Dam, both in Westerly. Removal of the dams not only restored wildlife habitat, it should also mitigate flooding in future storms.
The Pawcatuck has a long history of industrial use. At one point, as many as 10 dams stretched across the river to power mills built upon its banks. The dams fell out of use as an energy source, but they remained as obstacles to herring and shad, which aren’t strong swimmers and can’t jump the way salmon do.
Some of the dams washed out, but in recent years, a host of public and private agencies have worked to raze them or build alternative passageways for fish. The groups include the Nature Conservancy, the DEM, Fish and Wildlife and the Wood Pawcatuck Watershed Association.
To help restore fish runs, there’s a moratorium on fishing for river herring and shad in Rhode Island. Additionally, in the Pawcatuck, the DEM has worked to lend a hand by netting herring in the lower portions of the river and transporting them up to Worden Pond so that their young will become imprinted and return there year after year. The agency also brings in shad from the Connecticut River in Massachusetts to expand the native population in the river.
“They really jump-started the run once the dams came out,” Paton said.
It’s easy to overlook the humble herring. Although it’s a sleek and slender fish, it’s small and lacks much color.
But it’s an invaluable link in the food chain, serving as prey for bigger fish like striped bass and bluefish as well as wading birds, raptors and seabirds. A thriving herring run in the Pawcatuck can only help the commercial and recreational fishing industries and have positive effects throughout the ecosystem.
“They’re a foundational species,” Lundberg said. “They’re so important to the system.”
Herring are born in freshwater ponds and lakes, and then swim out to sea, where they spend years growing to adulthood before returning to their birthplace to spawn. The fish swimming upriver now will head back to the open ocean in the late summer and early fall.
Lundberg studies human impacts on river systems but she’s only started learning more about herring through the tagging project.
“They’re way more charismatic,” she said. “I didn’t know I’d love river herring as much as I do.”
—akuffner@providencejournal.com
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