Herring Monitoring

A spectacular migration occurs each spring in the Mystic River.

What are River Herring?

Two species of river herring migrate up the Mystic River from the ocean each spring: Alewife (Alosa psuedoharenous) and Blueback Herring (Alosa aestivalis). Both fish are anadromous: they spend most of their lives at sea and return to freshwater habitats to spawn, or lay eggs. River herring are an important part of the food web; healthy populations indicate a healthy ecosystem!

Why monitor River Herring?

Since the early 1900's the river herring population in the Mystic has drastically declined due to by-catch, habitat loss and degradation, water pollution, poaching, access to spawning habitat, and natural predators. They are now a threatened species. 

For years, a volunteer-run bucket brigade hoisted the fish over the dam- one year they moved over 17,000 fish! Thanks to the 2011 DCR Upper Mystic Lake Dam Rehabilitation project, a new fish ladder allows river herring to pass through the dam and into the lake. We want to know how many river herring are returning to the Mystic! 

What is the Herring Monitoring Program?

Over 90 volunteers help us count herring as they pass through the fish ladder at the DCR Mystic Lakes Dam. Counting occurs each spring (April - June) following the Massachusetts Division of Marine Fisheries (MA-DMF) protocol. The data collected is used to estimate the total herring run size in the Mystic River and is shared with the MA-DMF to help inform trends across the Commonwealth. YOU can be a citizen scientist and help collect valuable data about herring populations. MyRWA would like to thank the Massachusetts Division of Marine Fisheries. Massachusetts Department of Conservation and Recreation, Medford Boat Club and all of the monitors for supporting this program.

To find out more about this project email erica.wood@mysticriver.org. 

Herring Education Project

We're working with youth to raise awareness of this hidden migration! Launched in 2017, the Herring Education Project connects students and others to the remarkable river herring migration and the science behind it using technology, data gathering and analysis, curriculum, and field visits. We've worked with hundreds of students so far this year--bringing the Mystic River to classrooms through engaging, hands-on presentations, and inviting students to experience the migration in person at the Mystic Lakes Dam. 

YOU can also connect with the herring migration and help us count fish online! 

Herring Run Data

Herring Graph.JPG


2019: Estimated run size of 789,000

2018: Estimated run size of 589,924 +/1 74,087 herring.

2017: 91,997 herring counted resulting in an estimated run size of 630,098 +/- 60,599 herring.

2016: 62,562 herring were counted yielding an estimated run size of 448,060 +/- 48,113 herring.

2015: 57,617 herring were observed resulting in an estimated 477,827 +/- 40,674 herring run size.

2014: 31,063 herring were counted resulting in an estimated 239,059 +/- 37,288 herring run size.

2013: 23,635 herring were observed yielding an estimated run size of 193,125 +/- 24,250 herring.

2012: 21,052 herring were counted by citizen scientists. Using modeling software provided by the MA-DMF, the Mystic River herring run was estimated to be 198,932 +/- 18,062 herring. This was the first year of the Mystic River Herring Monitoring Program.

Eel Monitoring

MyRWA also monitors American Eel (Anguilla rostrata) passing through the Upper Mystic Lake Dam. Eels travel through the dam via a ramp to the right of the fish ladder and are counted by MyRWA staff and the the Massachusetts Division of Marine Fisheries.