Tidmarsh Herring Count Project

Volunteers counting herring in a restored cold-stream at Tidmarsh Wildlife Sanctuary
Tidmarsh Wildlife Sanctuary

Why Count Fish?


River Herring are anadromous (migratory) fish that consist of two species—Alewife (Alosa pseudoharengus) and Blueback Herring (Alosa aestivalis). They live in the ocean for most of their lives, but each spring the adults (3+ years) swim up rivers to spawn. At Tidmarsh Wildlife Sanctuary, these species enter Beaver Dam Brook where the Alewife spawn in upstream spawning grounds (in this case, Fresh Pond) and the Blueback, who arrive somewhat later, spawn in the riverine system. Typically the juvenile fish spend only a few months in this freshwater system and the return to the estuaries and, eventually, to the ocean to live as adults.

Brook Trout (Salvelinus fontinalis) is Massachusetts's only native trout species, and they require clear, cold, well-oxygenated water year-round. They are threatened by development, pollution, and climate change impacts that alter and remove suitable habitat. Mass Audubon and many community partners recently restored a section of cold-water stream that runs through the sanctuary, and we are hopeful that these conservation efforts will help bring back the trout population that once resided in this area.

Fish counts provide invaluable data to conservation efforts. The Tidmarsh Herring Count Project is focused on documenting the number of fish that make it up Beaver Dam Brook en route to Fresh Pond or to elsewhere in the riverine system to spawn. This count provides the sanctuary with important data about the post-restoration return of nature to Tidmarsh.


How to Participate


Thank you for your interest in volunteering to help with this important work! 

We are currently at capacity for 2021 Herring Count volunteers. However, if you'd still like to participate, we encourage you to add yourself to the Herring Count Volunteer Waitlist.

Join the waitlist >

The project's counting season typically runs from April–May. During this period, volunteers take on a recurring shift each week where they complete a 10-minute count at each of Tidmarsh's two streams.


Educational Resources


If you are interested in standards-aligned curriculum—including remote learning options and field trips—please contact us.

MA Division of Marine Fisheries

US Fish & Wildlife Service

Other Resources


Project Partners


This project is made possible through a partnership of the following organizations:

  • Mass Audubon's Tidmarsh Wildlife Sanctuary
  • Living Observatory
  • Mass Bays
  • North & South Rivers Watershed Association (NSRWA)
  • Responsive Environments Group at the MIT Media Lab
  • TerraCorps