Atlantic Salmon Ecosystems Research

We work to recover endangered U.S. Atlantic salmon populations and to conserve other native and sea-run fish and the ecosystems where these fish live.

New England/Mid-Atlantic

Graphic showing the life cycle of Atlantic salmon. Steps from egg to smolt are shown on a curved line superimposed over a dark shaded section of the graphic representing freshwater on land. The curve continues into a lighter shaded area that is the ocean, with steps along the way as the fish matures. Text boxes along the bottom half of the graphic provide more detail on threats to habitat and marine survival as well as predators. — Atlantic salmon begin their life cycle in rivers in Maine. Over several years they grow from eggs to fry to parr. After smolting, they travel through the Gulf of Maine into the North Atlantic as far as the coast of Greenland where they reach maturity before returning to Maine rivers to spawn. Credit: NOAA Fisheries

Recovering an Historic Population

Atlantic salmon have been listed under the Endangered Species Act since 2000. Our team studies what’s causing continued low numbers of U.S. Atlantic salmon to help managers develop plans to restore a sustainable population. Given their critically low numbers, NOAA Fisheries designated the remaining populations of U.S. Atlantic salmon as a Species in the Spotlight. Our work supports NOAA’s Atlantic Salmon Recovery Plan.

Atlantic salmon are diadromous, which means they spend part of their lives in freshwater and part in saltwater. They spawn in rivers, and juveniles spend the first 1 to 3 years of their life in Maine rivers. The juvenile salmon then migrate to the ocean for 1 to 3 years to feed, grow, and mature before returning to their home river to spawn.

Five silvery Atlantic salmon photographed from below are swimming in clear water just above some large rocks. — Atlantic salmon swimming upriver in Maine to spawn. Credit: Maine Department of Marine Resources/Casey Clark

Why Are Wild Atlantic Salmon Scarce?

Habitat destruction, dams, overfishing, and climate change contribute to low wild Atlantic salmon population levels. Historically, Atlantic salmon returned by the tens of thousands to most major rivers of New England. Now they only return in small numbers (fewer than 1,000 annually) to fewer than ten rivers in Maine.

Farm-Raised Atlantic Salmon Feed the Market

If Atlantic salmon are endangered, why can you buy them in local markets? The Atlantic salmon in the market are the same species as the endangered ones but are farmed from domesticated populations. Commercial aquaculture companies raise salmon in freshwater hatcheries on land. After the salmon smolt, the companies transfer them to either land-based saltwater tanks or to net pens in coastal waters.

Farmed salmon are bred for characteristics desirable in captivity but not for living in the wild. For example, farmed salmon are bred to grow very fast and can reach market size in less than 2 years, while wild salmon may take 3 to 6 years to reach a similar size.

A major challenge for NOAA is to support the growth of the U.S. aquaculture industry while also protecting our wild stocks. Negative consequences for wild stocks can arise from aquaculture production. For example, aquacultured salmon could escape into the wild and transfer genetic material, disease, or parasites to wild salmon. Finding solutions to these issues benefits both aquaculture and conservation.

Other Diadromous Fish We Study

Atlantic salmon are not the only fish in the Northeast and Mid-Atlantic that use both freshwater and ocean habitats. We also study these fish and the ecosystems they use, from headwater brooks to the North Atlantic. This project develops models and strategies for species that include:

River herring (alewife and blueback herring)
American shad
American eel
Sea lamprey
Rainbow smelt
Striped bass

Studying Atlantic Salmon to Promote their Recovery

An Ecosystem Approach

Atlantic salmon are part of a community of sea-run fish native to northeastern U.S. rivers. For populations to return to a sustainable level, managers believe it will take ecosystem recovery. They are focusing efforts on the habitat needs not only for salmon but multiple sea-run species.

Our work to recover Atlantic salmon and their habitat>

Population Management and Assessment

Atlantic salmon recovery is managed under U.S. laws and through international cooperation. To support these efforts, we conduct annual evaluations of abundance and freshwater distribution of salmon in Maine rivers as well as harvest in international waters. To do that, we need to gather data throughout the year on trends in the population and their environment.

How we monitor and assess Atlantic salmon populations >

Fish Passage and Dams

Given the critical importance of fish passage and river habitat, we also work to understand salmon success in moving through watersheds and dams. We study the upstream migration of adults to spawning and nursery areas and the downstream migration of juveniles to the ocean.

Atlantic salmon fish passage and dams>

Ocean Ecology and Atlantic Salmon

Salmon migrate out of U.S. waters, so we also study how conditions in the ocean that might affect growth and survival.

How we monitor fisheries and study Atlantic salmon ocean ecology>

International Atlantic Salmon Research

Our scientific support of international efforts ranges from studying ocean migration to sampling fisheries in Greenland to collaborating on stock assessments and management advice in international meetings.

Our international Atlantic salmon research and assessments>