One Fish, Two Fish: This Year's Mystic Herring Count Goes Online

May 29, 2020

Barbara Moran

Herring migrate up the Mystic River to spawn. This year, the Mystic River Watershed Association is using an underwater camera to count the fish, instead of people on site. (Mystic River Watershed Association)

Last year, about 789,000 river herring swam up the Mystic River to to spawn. How do we know this? Because volunteers counted them.

And even though the coronavirus pandemic is limiting in-person counting this year, volunteers have a plan B.

"We're actually really relying on our underwater fish cam," says Erica Wood, communications and outreach manager for the Mystic River Watershed Association (MRWA), which organizes the annual count. "This year it's really going to be the dataset we use to find out how many fish migrated up the Mystic."

Usually, volunteers stand by the fish ladder at the Mystic Lakes Dam and count fish for ten minutes every hour, from 7 a.m. to 7 p.m., every day. The volunteers start counting in April when the herring start running, and stop in July when the fish are finished. They send the data to the state Division of Marine Fisheries, which plugs the numbers into a statistical model and estimates the population size.

But this year, MRWA officials decided it was too risky to post volunteers at the fish ladder on the Mystic Lakes Dam — too many gates and lockboxes to touch.

"We just didn't want to expose anyone to unnecessary germs," Wood says.

The group has used the underwater camera in the past, to see what the herring are doing at night, and to double-check the numbers that volunteers collect on the surface. This year the fish cam will provide the primary data.

The new method does have some advantages — now anyone can help count fish from the comfort of their couch. And the website also offers daily numbers, charts, and a "leaderboard," for the hyper-competitive and data-driven among us.

Wood says they’re hoping that close to a million herring make it up the Mystic this year. That's a big increase from the measly 200,000 counted in 2012, when the fish ladder in Mystic Lakes Dam was installed. She says the return of the river herring has helped restore the ecosystem, improving the habitat for bald eagles and black-crowned night-herons that feed on the fish. This year the success story seems on track to continue, even if we're just watching from home.