Nashoba Brook, at the footbridge. Photo by Jennifer Lord Paluzzi

Column: Restoring migratory fish to Nashoba Brook 

By Alison Field-Juma  OARS Executive Director
February 2, 2024

The column “Wildlife, Safety Concerns at Warner’s Pond” by Friends of Warner’s Pond (11/10/23) requires correction regarding diadromous fish.  

OARS interviewed Ben German, Marine Habitat Resource Specialist with NOAA Fisheries’ Habitat and Ecosystem Services Division, to provide the facts. The full version is at 

What are diadromous fish? Diadromous (migratory) fish include both anadromous fish (live in the ocean and spawn in fresh water) and catadromous fish (the reverse). Anadromous fish include blueback herring, alewife, shad, and lamprey; catadromous fish include the American eel. Restoring self-sustaining populations of these five fish species is the goal, reestablishing an essential connection between the Gulf of Maine and our watershed. 

Why restore migratory fish? Migratory fish are a key piece of a resilient and diverse aquatic ecosystem. In fresh water, they are food for sport fish, otters, eagles, and other wildlife. They are critical to dispersal of endangered freshwater mussels which filter pollutants from river water. In salt water, migratory fish support the struggling commercial fisheries, recreational fishing, marine mammals, and the ecosystem. 

Is this watershed important? The Sudbury, Assabet and Concord is one of the closest spawning habitats for fish migrating from the Gulf of Maine up the Merrimack River. The fish deplete their energy reserves to reach suitable places to spawn. Fewer barriers and better access to spawning habitat lead to better reproductive success for migratory fish. Fish are more likely to survive and breed successfully if they have a closer habitat and fewer barriers. Rivers like the Concord and their connected streams, lakes, ponds, and wetlands are vitally important to the success of migratory fish. 

Why is Nashoba Brook so important? With the Talbot dam in Billerica removed (2024/25), there will be no impassable barriers between Nashoba Brook and the ocean. Opening the Concord River is like opening a highway, but if fish can’t reach spawning habitat (the residential neighborhoods), they will not produce sustainable populations. Alewife require quiet water to spawn and for their young to grow but there is very little quiet water accessible to alewife.  

Nashoba Brook is one of the first such tributaries that enters the river section opened by the Talbot dam removal. Simply removing the Talbot dam opens the possibility of sustainable migratory fish populations. A diversity of accessible habitats increases the likelihood of success. This is why removing Warner’s Pond dam is such a high priority for migratory fish restoration.