Green Lake National Fish Hatchery
Northeast Region
Rt. 190
One Hatchery Way
Ellsworth, ME 04605
(207) 667-9531
Fax: (207) 667-5559

Atlantic Salmon - Salmo salar

Atlantic salmon. Credit: USFWS
Biologist holding Atlantic salmon. Credit: USFWS

Salmon Lifespan

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Maine's seven protected rivers. Credit: USFWS
Map of Maine's seven protected rivers. Credit: USFWS

The National Marine Fisheries service (NMFS) and the United States Fish and Wildlife Service (USFWS) determined that the Atlantic salmon populations are, as a group, reproductively isolated and discrete. A single Distinct Population Segment (DPS) composed of seven river populations of Atlantic salmon was originally proposed for listing as threatened on September 29, 1995 (an eighth river has since been added). The Services named these seven rivers the “Gulf of Maine DPS”. The Dennys river in East Machias (one of the rivers of the Gulf of Maine DPS), along with the Penobscot, the Union, the St. Croix, the Merrimack and the Saco rivers are stocked annually by the Green Lake National Fish Hatchery with Atlantic salmon smolts and parr. Atlantic salmon were officially listed as Endangered on November 17, 2000.

The decline of the Atlantic salmon

Although there is no definitive answer for the decline of Atlantic salmon, scientists have speculated on several logical ­ essentially environmental ­ reasons for decline such as river-water use, watershed land use, air-borne contaminants and human and environmental factors at sea.

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Other factors have contributed as well such as forest management practices (stream siltation, tree removal which causes loss of shade and increased water temperatures); and other agricultural activities associated with water usage and withdrawals from these rivers. 

In addressing these particular issues, the USFWS partnering with agencies, private organizations and landowners developed the Fish Passage Program, to reconnect aquatic species to historical habitats, and restore natural flows and fish migrations. Additionally, the United States (in partnership with the North Atlantic Salmon Conservation Organization “NASCO"), developed the Fishery Management Plan - effectively prohibiting the possession of Atlantic salmon in the Exclusive Economic Zone (meaning, from the state boundary to the 200-mile limit at sea). The NASCO also negotiated quotas for the protection of Atlantic salmon stocks harvested in marine commercial fisheries.  The state of Maine currently has closed all rivers in the state to fishing for Atlantic salmon.

Biologist performing genetic testing on salmon. Credit: USFWS
Photo of biologist performing genetic testing on salmon. Credit: USFWS
Atlantic Salmon Commission staff assisting Green Lake NFH staff pick eggs. Credit: USFWS
Atlantic Salmon Commission staff assisting Green Lake NFH staff pick eggs. Credit: USFWS

Beyond the environmental factors affecting the decline of the Atlantic salmon there are commercial issues as well. Aquaculture facilities are raising strains of Atlantic salmon in net pens only 20km from the mouths of five DPS rivers. The escape of farmed salmon into the rivers and the possibility of their inter-breeding with native wild salmon threaten the genetic integrity of Atlantic salmon. Also, consider the increased vulnerability of the wild stocks to the diseases the aquacultured salmon may carry. To safeguard the native salmon from potential diseases carried by aquacultured salmon, barriers have been placed in some of the river systems which allow for the monitoring of Atlantic salmon before they enter these rivers.

Green Lake National Fish Hatchery’s part in the recovery, restoration and rehabilitation of Atlantic salmon

Keith Boyer, USFWS Green Lake NFH, holding adult Atlantic salmon. Credit: USFWS
Keith Boyer, USFWS Green Lake NFH, holding adult Atlantic salmon. Credit: USFWS

The 1991-1995 cooperative agreement between the USFWS and the Maine Atlantic Sea Run Salmon Commission for Atlantic salmon management delicately defined the difference between “restoration” and “rehabilitation” of the Atlantic salmon in fisheries program management. Although both programs shared the goal of re-establishing self-sustaining Atlantic salmon populations to the rivers by examining habitat and enhancing natural reproductive opportunity, each had it’s own focus and role. The hatcheries role was to utilize the genetic material that was as similar as possible to the river itself ­ to grow disease-free, genetically-sound Atlantic salmon that would successfully make the transition from the hatchery environment to the wild. To accomplish this, broodstock are maintained from each of the natal rivers and spawned at the hatcheries ­ preserving the genetic diversity of each river. The eggs, fry, parr, and smolts are monitored ­ tagged at the appropriate time to enable tracking of genetics and to evaluate hatchery releases.

Spawning an Atlantic salmon. Credit: USFWS
Spawning an Atlantic salmon. Credit: USFWS

Not only does the USFWS Fisheries program restore Atlantic salmon to rivers where the salmon populations have been lost, but they also work to rehabilitate rivers where the genetic legacy still exists but is waning. Careful stocking of Atlantic salmon reared from river-specific wild stocks helps to boost the numbers of returning salmon and preserves this genetic legacy. Recovery is the process where the Service will attempt to save these populations from extinction. A detailed Recovery Plan is being drafted under the Endangered Species Act to protect and conserve Atlantic salmon because it is on the brink of extinction. The Plan identifies a series of strategies ­ the sole goal is to ensure the species can complete its life cycle ad infinitum and ultimately be removed from the Endangered Species list.

Bringing the Atlantic salmon back to the rivers

Green Lake annually stocks 650,000+ yearling smolts (8” fish) and 350,000+ fall parr (3-5” fish). These fish are released in Atlantic salmon restoration/recovery rivers of the Gulf of Maine. Specifically, fish are released into the Penobscot River basin (ME), St. Croix River basin (ME), Merrimack River basin (MA-NH), Saco River basin (ME-NH), and the Dennys River basin (ME). In Maine’s rivers, salmon take two years to reach the smolt stage, at which time they’re ready to migrate to sea. The recovery and restoration of the Dennys river salmon population as well as the restoration of five other rivers begins at the Green Lake National Fish Hatchery.

A higher percentage of the fish obtain smolt size in one year’s time than is possible in the wild. The controlled environment at the Hatchery assures that each spring large numbers of Atlantic salmon begin the migration to the ocean.

Bringing Atlantic salmon back to the Penobscot River has been the major restoration effort in Maine, and the most successful in New England. Three out of every four Atlantic salmon returning to US waters came from the Green Lake Hatchery.


  • In 2002, Green Lake staff reared and stocked 655,000 yearling Atlantic salmon smolts and 429,000 Atlantic salmon parr throughout the Gulf of Maine Ecosystem.
  • In 2002, 82,000 Dennys River Atlantic salmon were distributed as part of the recovery efforts for the endangered population.
  • In 2002 hatchery staff, in partnership with National Marine Fisheries Service (NMFS), tagged 232,000 Atlantic salmon smolts using a visible elastomer implant an additional 134,000 fall parr were marked via a fin clip.
  • All fish reared at the Hatchery are genetically marked to evaluate hatchery populations.

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Last updated: February 22, 2016
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