Alewife Brook: A Spawning Pathway in Danger

Updated: Jun 26

The Alewife Brook flows from Chebacco Lake into the Essex River and the North Atlantic Ocean. The brook is a vital path for river herring, as it provides more than 200 potential acres of spawning habitat for a fish species known as the Alewife. Alewives spend the majority of their lifetime in the ocean; however, they spawn in freshwater lakes. Thus, they are classified as an anadromous fish species (NOAA).


The Alewife Brook is one of the few river herring runs that has not been obstructed by any man-made dams, making it an ideal home for Alewives. However, passage through this brook is becoming increasingly challenging due to multiple factors such as beaver-made dams, low water levels, and increased siltation, which makes it difficult for the fish to follow a clear path. Additionally, sewage systems have disposed of some waste in the brook, which– along with many other factors has led to eutrophication (increased nutrient buildup) and algal blooms blocking this pathway. These conditions are also detrimental to aquatic life and other residents of the watershed, with dirty waters and restricted movement.


Unfortunately, the Alewife population has suffered the impacts of this blockage. Their numbers and presence in Alewife Brook have decreased significantly. The Mass Division of Marine Fisheries has estimated a decline from 43,000 to 4,800 from 2016 to 2020. This has disrupted the ecosystem in the Chebacco Lake Watershed, as the fish offer several benefits, mainly serving as a crucial part of other species’ diets. Alewives are a “healthier prey item for fish-eating birds than resident freshwater fish because they have not accrued these toxins in their bodies”. The importance of their presence is reflected by the mere fact that the brook is named Alewife Brook!


Seaside Sustainability and other groups will begin efforts to restore the health of Alewife Brook in the coming weeks. Reducing plant blockage and future growth will be the primary concern addressed in these efforts, as the group hopes to open up this vital path for river herring. The work Seaside Sustainability and all of those involved in the project is vital toward the survival and protection of this essential spawning ground and watershed ecosystem.


To find out more about Seaside Sustainability’s efforts in restoring the Alewife Brook and Chebacco Lake, click here. Discover the rich background of the ecosystem in our blog on the History of the Chebacco Lake Watershed.

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