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Part 2 of Atlantic Salmon Series: Myriad of Challenges to Survive at Sea

Spawning Salmon               

Alevin

  Fry and Parr

Smolt

Grilse

As anadromous1 fish, Atlantic salmon spend much of their lives at sea. However, survival rates for salmon born in U.S. rivers are low in the ocean. To help recover Atlantic salmon, we need to know more about the risks they face at sea.

We conduct research to study the travels of Atlantic salmon, and how changes in environmental conditions (such as water temperature and prey availability) and impacts of commercial fisheries outside of the U.S. may be affecting salmon recovery.  

Tagging Studies

In the 1960’s, scientists started tagging U.S. Atlantic salmon smolts (young salmon) with plastic identification tags.  Scientists and managers wanted to know if the fish being caught in commercial fisheries off the coast of West Greenland were actually fish that were migrating from U.S. waters. Between 1962 and 1996, more than 1.5 million salmon from New England rivers, primarily hatchery reared smolts, were tagged and released.

Some of the recovered tags came from fish caught in U.S. and Canadian waters while others came from fish caught at sea and off the coast of Greenland. Tagged fish were caught in nearshore gillnet fisheries for salmon and to a lesser extent in cod traps, mackerel traps and saltwater weirs. Some fish were even caught by recreational anglers, in fishway traps around dams and during research surveys. From this research, we also know that some U.S. origin fish are being caught in fisheries operating off of Labrador, Canada and St. Pierre et Miquelon (an island territory of France that lies just south of Newfoundland, Canada). However, more than half of the tags recovered came from Greenland.  While the U.S. near shore fisheries are no longer in operation, catch in distant water fisheries remains a concern for Atlantic salmon.

The Salmon’s Life Cycle

Atlantic salmon adults return from sea to spawn in their natal2 rivers in Maine in late autumn. Fertilized eggs are buried under 5 - 8 inches of gravel in "redds"3. Due to the Northeast's cold winters, eggs incubate slowly and do not hatch until March or April. Sac fry, or alevin, remain hidden in redds until they deplete their yolk sac reserves (mid-May).

They emerge as fry. Now at greater risk from predators, fry develop lateral "parr" markings as camouflage and enter the parr life stage.  Parr can remain in freshwater 1-3 years (typically 2 years) until they undergo a physiological transformation (smoltification) to develop a tolerance for saltwater.

Smolts migrate down river. Once they enter the ocean they are called postsmolts.  Postsmolts migrate up to Newfoundland and Labrador by mid-summer. Some of these fish migrate home to their natal river to spawn the following year as grilse, having spent one year at sea. Others continue their migration further north to Greenland. 

After feeding on capelin and other prey items along the Greenland coast, these fish begin the long migration home to spawn, having spent 2 winters at sea. 

 

Fishery Sampling Program

NOAA scientists collect a variety of biological samples from fish to help us understand where fish are born and how healthy they are. If we know where a fish is born, when it is tagged and recaptured, this information can help us piece together how far the fish travelled.

NOAA Fisheries staff oversee an annual sampling program for the Greenland fishery through the North Atlantic Salmon Conservation Organization. We work with scientists from resource agencies in Canada, Ireland, United Kingdom, and the Greenland Institute for Natural Resources to collect information and samples from the harvested Atlantic salmon.

Samplers are stationed in various communities throughout Greenland. They collect length and weight information on salmon harvested to gain information on the overall health and size of fish in the population subjected to the fishery; scale samples to determine their age; and tissue samples to determine where the fish came from (i.e. North America or Europe). This information is combined with data from all countries where salmon are harvested.  Scientists can then use these data to estimate Atlantic salmon population abundance in the ocean and provide recommendations to help better manage and control catch for from the Greenland fishery.  

Stronger International Management Sought

Armed with the collected scientific information, we are better able to make a case for stronger protections for salmon in various international fisheries. 

We use this and other information when we participate in ongoing discussions through the North Atlantic Salmon Conservation Organization and other international forums to encourage adoption of international and country-specific management measures.

Because Atlantic salmon can migrate long distances and face challenges along the way, all of this work is critical if we are to prevent Atlantic salmon extinction in U.S. waters. 

Status of Atlantic salmon in U.S.

Gulf of Maine Atlantic Salmon Distinct Population Segment

Endangered (U.S. Endangered Species Act)

  • The Penobscot River in Maine has the largest run of Atlantic salmon in the U.S.
  • On the Penobscot, 2013 was the third year in a row where fewer than 1,000 adult salmon returned annually to spawn.
  • In 2013, returning spawners were at the lowest level in 37 years.

In Part 3 of this series, we'll share the work being done with small dam owners to improve access to habitat on the many tributaries and streams that connect to the Penobscot River. Approximately 470 dams impair or block access to approximately 90 percent of freshwater habitat in the Penobscot watershed, which is needed to support Atlantic salmon spawning and rearing of juveniles.

1spends a portion of its life in freshwater and at-sea

2the river the fish was born in

3an area of disturbed gravel containing one or more nests

More information:

More on satellite tagging work by NOAA Fisheries scientists

Description of the Historic US Atlantic Salmon (Salmo salar L.) Tagging Programs and Subsequent Databases

The North Atlantic Salmon Conservation Organization

International Atlantic Salmon Research Board

U.S. Fish and Wildlife Service’s blog on Atlantic salmon