Atlantic Salmon Population Monitoring and Stock Assessment

Collaborative monitoring and conservation biology efforts by NOAA scientists provides information needed to  support to fisheries management and population conservation efforts for Atlantic salmon in the United States and internationally for:

• The federal Atlantic Salmon Management Plan, which complements state programs in coastal and inland waters
• Periodic analysis of species’ status under ESA as summarized in  Atlantic Salmon  5-year Review Summary and Evaluation 
• Meeting United States responsibilities as a signatory nation to the North Atlantic Salmon Conservation Organization 

Our assessment work provides managers information about Atlantic salmon population status, particularly relative abundance and trends.  These data are summarized in the US Atlantic Salmon Assessment Committee annual report and databases.

Monitoring

The U.S. Atlantic salmon populations are sometimes easy, and sometimes difficult, to monitor. They are relatively easy to monitor when they are in rivers. However, we need to study many rivers to understand and track the trends. Once juvenile salmon migrate from freshwater, they become a small fish in a very large ocean. They are more difficult to study given their vast marine range and the difficulty of collecting them there. Modern tools like telemetry (a way to remotely follow the movements of individual fish) allow us to monitor movement as never before.

Traps

Researchers use different methods for monitoring and counting Atlantic salmon. Our partners at the Maine Department of Marine Resources are key for much of this work. Traps, sometimes associated with a dam, are installed in some rivers. These traps capture adult salmon as they migrate up a river to spawn. As juvenile salmon migrate down river to the ocean, they can be captured by using a rotary screw trap. 

Manual River Surveys

For rivers without a trap, researchers sometimes snorkel the waters, counting the adults they see, or more often counting the nests they see from a canoe. 

Juvenile salmon can be sampled and counted using an electrofishing backpack which sends a small jolt of electricity through the water. This temporarily stuns encountered fish so they can be scooped up with a net, sampled, and returned alive to the river. 

Sampling in the Ocean

We capture salmon in the open ocean using surface trawl nets and gillnets. In coastal areas where salmon congregate to feed, such as off the coast of Greenland, local residents harvest them using gillnets. Scientists survey the catch to have access to them for sampling. We have even started collecting salmon in Greenland waters so that we can collect samples and tag and release these fish alive.

Data Synthesis and Reporting

Once all these datasets are assembled, the U.S. Atlantic Salmon Assessment Committee conducts the annual stock assessment to determine the status of the U.S. salmon population. This team of state and federal biologists is tasked with compiling and reporting data on the species throughout New England. Historically, the stock assessment focused on salmon data collected from all U.S. populations, from Connecticut to Maine. The U.S. stock assessment now focus on endangered Maine  populations as they are the only active recovery-scale programs. Our assessment efforts are aligned with the guidelines set forth for a viable salmon population, describing the abundance, growth, spatial distribution, and genetic diversity of the population of study.

Ageing Atlantic Salmon

Our image analysis laboratory supports projects that require a microscope and or a computer to analyze images. This is where we review the growth patterns preserved on scales collected from sampled Atlantic salmon to determine the age and origin of the fish.

Climate Vulnerability

While climate impacts have been ongoing since the Industrial Revolution, rates of change have accelerated. NOAA Fisheries has conducted detailed vulnerability assessments that evaluated both climate sensitivity and exposure of a number of marine species. 

Of the 82 species assessed in the Northeast, Atlantic salmon were the most highly vulnerable finfish in New England. Because of Atlantic salmon’s endangered status as well as exposure and sensitivity to climate stressors, NOAA convened a Climate Scenario Planning (pdf, 91 pgs) workshop. An expert team examined what could be done to better manage the species in the presence of a changing climate. This effort captured uncertainties and developed options that will meet management goals. Scientists use the resulting recommendations to accelerate research into identifying and maintaining resilient nursery areas, and to better understand the salmon’s future ecosystem.