Volunteer River Herring Monitoring at Beaver Dam Brook and Manomet Brook

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. In April and May, the adult herring enter the streams along the Massachusetts coast, including Beaver Dam Brook where the alewife swim up to Fresh Pond and the blueback herring, who arrive somewhat later, spawn in the riverine system. Once they spawn, the adults head back to the ocean. Once the eggs hatch, the juveniles will spend a few months in the freshwater habitat before they too head to the ocean to live as adults.

Brook Trout (Salvelinus fontinalis) are 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. Manomet Brook and Foothills Preserve restorations provide potentially suitable cold-water habitat.

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. The counts are reported to the Massachusetts Department of Marine Fisheries and become part of the Massachusetts state count. The project also contributes important information to research about the return of biodiversity to the Tidmarsh Headwaters and Manomet Brook restoration projects. The annual count typically occurs throughout April and May.

The Tidmarsh Herring Count is a collaboration between Mass Audubon, Living Observatory, and the Town of Plymouth. The lead scientist on the project is Dr. Sara Grady, Mass Audubon Senior Coastal Ecologist.

This group of over 20 herring sped under the Beaver Dam Brook bridge on May 7, 2017.


Recent Updates

First Fish Seen On May 1st!

By Sara P. Grady on May 2, 2025
Some fish have arrived! So far, five river herring have been seen at Bridge #2. Right now, that was the only sighting, but there's still the whole month to go as well. The lowest year to date (2018) had 16 herring sighted by May 2nd and a total of 38 by May 31st, so hopefully this year can exceed that and perhaps rival previous, higher years. It is exciting that there are river herring traveling through the system - keep collecting that data so we can have a valid population estimate at the end of the season. Happy May!

2025 Herring Counts Begin Tuesday April 1st!

By Kimberly Snyder on March 25, 2025
That time of year is here again! Herring count trainings are scheduled for our new and returning volunteers!

Contributors

Sara P. Grady
Robert Vincent
Glorianna Davenport
Kimberly Snyder
researcher

Institutions

Mass Audubon
Living Observatory