Around Town, Only in Medford

Lights, Camera … Herring! Join Mystic River Count Online


The Mystic River’s herring migration in May and June will be online 24 hours day under a new project led by the Arlington-based Mystic River Watershed Association.

A underwater camera with a motion sensor at the Upper Mystic Lake dam fish ladder in Medford is recording and uploading clips in real time to the new project website.

You can see — and even count — how many fish are migrating up the Mystic. That helps researchers track how the herring migration changes over time. It only takes a few seconds to help record the number.

Last year, about 448,060 river herring swam upstream past Everett, Somerville, Medford and Arlington to the Mystic Lakes — a seven-mile journey.

The fish come from the ocean into fresh water each spring when water temperatures reach 55 degrees.

Patrick Herron, executive director of the watershed association said this project aims to bring the migration greater visibility.

To learn more and to help document the herring migration, see

For more information, see

2015 report

In a June 2015 news story titled “Citizen scientists document dramatic increase herring at Mystic Lakes Dam,” YourArlington reported that commenters expressed fear on the Arlington Email List that river herring were dying in great numbers at the Mystic Lakes Dam.

Whether the number of dying herring seen at the time was greater than usual was not known, but the number of herring successfully using the fish ladder to spawn had then increased significantly.

Ask the Mystic River Watershed Association, which has been working with hundreds of volunteers.

Since 2012, the volunteers have counted river herring passing through the fish ladder at Mystic Lakes Dam to spawn in Upper Mystic Lake. In 2015, the citizen scientists were able to document that an estimated nearly half a million river herring swam through the fish ladder to spawn — a 100-percent increase over the counts in the previous three years, a news release from the watershed says.

River herring collectively refer to two species of herring, Blueback (Alosa aestivilis) and Alewife (Alosa pseudoharengus). These two species are “anadromous” fish; they live the majority of their lives in saltwater but lay eggs (spawn) in fresh water.

The billions of river herring eggs that are produced in Upper Mystic Lake will develop into juvenile herring within just a few days. These juveniles will stay in the fresh water for as long as four months, before swimming downstream to live in estuarine waters. The river herring that survive will reach an age to reproduce after three to four years and usually return to the same waters where they were born.

The Mystic River is one of 78 river herring runs in Massachusetts. River herring are an important component of ocean fisheries, and they need access to freshwater systems to survive. Over the past several decades, populations of river herring have dramatically declined.

The watershed association works each year to train a set of volunteers to perform visual counts at the fish ladder Mystic Lakes Dam. The volunteers agree to perform at least one 10-minute observation each week. Volunteers in the 2015 program performed 680 10-minute observations and counted 57,617 fish. The observations and counted fish are plugged into a sophisticated model developed by the Division of Marine Fisheries that yields the population estimate of 477,827 (plus or minus 40,674) for 2015.

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