Tidmarsh Herring Count Project

River Herring (Alewife and Blueback species) are anadromous (migratory) fish. 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.

Herring counts are a way to document 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.

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Getting Started

Thank you for volunteering to help us with this important work! Before you begin, please take the time to review the instruction guide and watch the training video. This document contains a detailed overview of the counting process, including how to successfully count while watching the live video feed and how to submit your data.

Conduct a Count

  • Be sure to print out the Count Data Sheet so you can record counts by hand while watching the video feed. 
  • Click the "play" button once you're ready to begin your 10-minute count session.


Report the Data

After you have completed a 10-minute count session, please submit your data via the online form.

Submit Your Count >

Educational Resources

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

Mass Division of Marine Fisheries (DMF)

Herring Alliance 
River Herring Factsheet

US Fish & Wildlife Service 
River Herring: Alewife & Blueback Herring

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