environment Number of fish up at Mianus River
GREENWICH — When Central Greenwich resident Bob Stanton first volunteered at the Mianus Fish Ladder this spring, it was still chilly and he saw no fish. On days like that, he said it was easy to feel a sense of failure.
Then, the recent retiree saw the number 16 on the fish counter at the ladder, and he thought that was significant.
Seven weeks later, the counter registered 6,000 fish.
“You drive over the Post Road every day and you have no idea what’s going on,” Stanton said. “But there are 40,000 fish that went up that ladder and into the Mianus Pond. That’s a lot of fish.”
More than 40,000 alewives and blueback herring ascended Greenwich’s Mianus River Fish Ladder during the 2018 season, the highest number registered there in four years, according to a report from the state.
“Greenwich is fairly lucky to have a fish ladder and a counter,” said Sarah Coccaro, conservation resource manager for the town’s Conservation Commission. “We actually know what’s going through the fishway and how many.”
Alewife numbers doubled to 32,961 at Mianus, but only modest increases were seen across the state. Mianus River was one of only two locations to register increases in blueback herring, counting 8,202 of the fish, Coccaro said.
This increase likely means conditions at sea are improving for these fish, which make the long trip from the Atlantic Ocean upstream to freshwater to lay eggs. Successful alewife and blueback herring runs in turn increase the populations of striped bass, tuna, osprey, herons, humpback whales, dolphins and sea turtles.
The fishway is located at the Mianus Pond Dam, just north of Post Road and adjacent to the River House Adult Day Center in Cos Cob. It is manned by volunteers, and Coccaro was surprised by the number that turned up this year. She had 15 to 18 volunteers, enough that she had to turn people away.
“I feel lucky to be able to work there and work with volunteers who are truly passionate,” she said.
Stanton, who retired two years ago, started volunteering this spring. At first, he worried it would require technical skills he didn’t have, but he soon found his responsibilities were within his and any other volunteer’s ability.
A volunteer’s typical visit lasts 30 to 60 minutes — the time it takes to record the water temperature and height, check the eel nets and record the numbers, and catch the fish in the resting pools along the ladder to measure their size and condition.
Stanton brought his 5-year-old grandson along on one trip.
“He was really excited when we caught a fish,” Stanton said. “He said when he grows up, he wants to be a fish-counter. I took that as being a positive experience for him.”
Stanton recommends volunteering to any person interested in nature and fish. For those who can’t, he suggested attending the fish ladder’s yearly open house in spring or just stopping for ice cream at Gofer and asking for a tour.
Among fishways, Mianus a good indicator of what’s happening in the Atlantic Ocean, said Steve Gephard, a fish biologist with the state Department of Energy and Environmental Protection.
“If the numbers at Mianus go up, hopefully that means all fish all over Long Island Sound are doing well,” he said. “There’s no guarantee in that. We don’t fully understand what goes on once they get to the ocean.”
The number of alewives that come through a fishway depends on two factors: how much habitat and freshwater there is upstream and the survival rate of alewives at sea. Alewives return to freshwater after three to four years in the ocean.
More alewives and blueback herring in the oceans means more humpback whales, pods of dolphins and large sea turtles in Long Island Sound because they have a consistent food supply, according to Coccaro.
“If we don’t have those fish ladders, they’re not going to want to stop in Long Island Sound,” she said. “Towns and states doing an amazing job cleaning up, but we need to make sure (those animals) have a food source.”
More alewives and blue herring also means more of their predators, the commercially fished striped bass and tuna, Gephard said. Osprey, heron and eagle populations also rely on alewife and blue herring runs for food.
Osprey arrive in Connecticut at the same time as alewives, so a healthy fish population ensures the birds can recover from migrating and raise their young, he said.
The recovery is only partial, however. Gephard said numbers are still far below what they were in the 1980s.
“It’s not like we’re back to the good old days, but we took step in right direction,” he said. Biologists don’t know how exactly many fish Mianus can support if ocean conditions continue to improve, Gephard said. In the past, fish runs could reach 98,000 — three times this year’s number.
The decline started in 1986. By 2002, it caused the state to end the fish harvest. The Mianus fishway was built in the ’90s, during the decline, and it didn’t have a fish counter until 2007.
The state has 3,000 to 4,000 dams of varying heights, which block fish from migrating from saltwater to freshwater.
DEEP has identified five derelict dams for removal this summer, including the Flock Process Dam in Norwalk, which could increase alewife runs on the Norwalk River. DEEP also plans to build a fishway at Dolan Pond, benefiting fish going up the Connecticut River.
Municipalities and conservation groups are doing all they can in freshwater — cleaning the water, taking down dams and expanding freshwater habitats, Gephard said.
Saltwater habitats require more attention. The population of alewives and blueback herring are impacted when off-shore fisheries accidentally haul them up while fishing for Atlantic herring and mackerel, he said.
“As a fisheries management community, we need to do all we can do to minimize bycatch,” Gephard said. “It’s OK that people can fish for herring and mackerel, but we need to find ways of reducing alewife and blueback herring that they catch at the same time.”