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Do Not Disturb Migrating Sea Lamprey!

sea lamprey nesting

It’s that time of the year again when we witness the migration of hundreds of thousands of migratory fish moving up the Connecticut River and its tributaries to spawn. Amongst them are the native sea lamprey.  

Sea lampreys return to our freshwater systems to spawn, or reproduce, after spending a few years in the ocean, as parasitic fish. Upon reaching freshwater systems, the lampreys stop feeding with only one goal in mind, finding suitable habitat to build their nests and lay their eggs. Lampreys will not seek to prey on humans or other organisms during their migration. After spawning, the lampreys die, leaving behind a nutrient rich carcass, providing numerous ecological benefits. In turn, larval lampreys burrow in sandy substrate and filter feed in the river, acting as cleaners like mussels. They will reside in the river for 5 years, developing into juvenile lampreys and moving to the ocean for their adult years. They are native to the Connecticut River, and we work to protect and restore their population and habitats.  

A separate population of sea lamprey are found in Lake Champlain and the Great Lakes, and are managed as a nuisance, or invasive, species. The two separate populations are managed differently and it’s important that the public understands this difference and does not interfere with their migration on the Connecticut River.  

As of May 30, 2024, close to 50,000 sea lampreys have made it over the Holyoke dam, compared to 22,000 total in 2023. They will be more noticeable below barriers, such as dams and culverts, and around rocky riverbeds. We ask that you please do not disturb them.  

Sea lampreys are managed by the Connecticut River Migratory Fish Restoration Cooperative, comprised of fisheries experts from state agencies from CT, MA, VT and NH, as well as federal agencies and representatives from the public.  

Learn more at   


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