An endangered species, Atlantic salmon are now being raised in hatcheries and outfitted with satellite tags to keep track of their migration patterns.
The Atlantic salmon is actually one species within the genus Salmo. There are seven different species of Pacific salmon, which belong to the genus Oncorhynchus.
Atlantic salmon generally don't live long after spawning but are capable of surviving and spawning again. Most Pacific salmon die shortly after spawning, with the exception of steelhead.
Atlantic salmon used to be found from Long Island Sound to New England, but those populations no longer exist in these rivers. Currently U.S. Atlantic salmon are only found in a handful of rivers in Maine.
Atlantic salmon go to sea to grow. The energy content and abundance of food in the ocean is much higher than in freshwater, so fish are able to grow very big, very quickly. This is important because larger fish are less likely to be eaten and the females have more eggs. A lot of eggs are needed to produce enough juveniles that will grow to maturity and return to spawn and sustain the population.
Young Atlantic salmon (called "smolts") migrate to sea every year in the spring. The “smolt run” in the Gulf of Maine begins in the middle of April and is over by the beginning of June. Due to regional climate impacts, the smolt run is starting earlier than in the past. The run begins later at northern latitudes.
Atlantic salmon smolt are usually 2-3 years old when they begin their migration in U.S. waters, but migrating smolt are often older at higher latitudes.
North American Atlantic salmon migrate in the spring from the rivers where they were born. They move into the Labrador Sea for their first summer, autumn, and winter. The following spring they move to the coastal waters of Labrador and the Canadian Arctic, West Greenland, and sometimes to the waters of East Greenland. After a second winter at sea, adults from many populations are large and mature enough to spawn, and they migrate back to freshwater areas to reproduce.
A landlocked Atlantic salmon is a freshwater form of the sea-run Atlantic salmon. They are genetically considered a subspecies of the sea-run Atlantic salmon. They reside in lakes, never making the marine migration. They generally do not grow as large as sea-run fish, averaging between 12 and 20 inches long.
In fresh water, young salmon mostly eat small insects such as mayflies, stoneflies, caddisflies, blackflies, and riffle beetles. Sometimes they eat small amphibians and fish.
When they're in the ocean, young and adult salmon eat a wide variety of prey, including:
Just before adults migrate to estuaries to begin the spawning migration, they stop eating altogether.
In freshwater, juveniles are eaten by a variety of fish (smallmouth bass, striped bass, Northern pike, slimy sculpin, etc.), birds (kingfisher, double-crested cormorant, mergansers, osprey, blue heron, snowy egret, etc.), and mammals (otter, mink, etc.).
In the ocean, Atlantic salmon are eaten by:
Atlantic salmon are also caught for consumption by humans in targeted aboriginal or traditional First Nations fisheries.
The largest Atlantic salmon was 105 pounds and 60 inches. However, depending on how long they are at sea, adults returning to the Gulf of Maine rivers typically weigh approximately 7-12 lbs and are 28-32 inches long after 2 years at sea.
The maximum recorded age was 13 years old, but most Atlantic salmon that survive to reproduce live 5 to 8 years (1-7 years in fresh water, 1-6 years in the marine environment).
Almost always. While some straying has been documented, most spawning salmon return to the river in which they were born and sometimes they even home to the very stream of their birth.
Generally from 2,500 to 7,000 depending on the size of the female (larger females have more eggs), or about 600-800 eggs per pound of body weight.
The Endangered Species Act (ESA) is a law passed in 1973 that provides for the protection and conservation of species that are at very high risk of going extinct. Atlantic salmon populations in the Gulf of Maine are listed as endangered under the ESA. This means that they are in danger of extinction throughout all or part of their range. Before construction of dams in the early 1830s, more than 100,000 Atlantic salmon returned to U.S. rivers each year; now adult returns are usually less than 1,000.
There are many reasons why U.S. Atlantic salmon population abundances are so low. There are three primary causes:
Salmon are raised in hatcheries to supplement natural production in rivers. U.S. Atlantic salmon are endangered and are currently unable to produce enough juveniles under natural conditions in the rivers to support their populations. Therefore, juveniles are raised in hatcheries to various stages (i.e., fry, fingerling, parr, and smolt) to enhance survival at early life stages. Then they are stocked in the rivers so that they can migrate to sea then return to spawn after a few years. Stocking helps maintain endangered populations so they don’t go extinct. This gives scientists and managers more time to figure out how to restore thriving populations to Gulf of Maine rivers again.
From 2010-2015, releases of hatchery-raised Atlantic salmon smolt to supplement natural production in the streams of the Gulf of Maine resulted in adult spawning returns of approximately 0.08-0.71%. This low return rate is the result of numerous factors including high mortality in the river from downstream passage barriers and low marine survival.
Fish passage is essential for adult salmon to be able to travel upriver to spawn and for salmon smolts to be able to travel down river to reach the sea. A fish ladder, or fishway, is often constructed to help salmon swim upstream around a dam or a natural barrier that might prevent or impede progress to spawning grounds. Downstream passage of migrating smolts and some post-spawned adults past barriers is sometimes provided by constructing a bypass structure or by allowing sufficient amounts of water to spill over a dam.
Before the decline of Atlantic salmon, anglers competed annually to land the largest spring salmon. The Presidential Salmon Tradition was born out of a Penobscot River competition when, in 1912, Karl Anderson sent his winning 22-pound salmon to President Taft. The tradition was suspended due to low salmon abundance in 1992. President George H. W. Bush was the last President to receive a Presidential salmon.
Thanks to Ruth Haas-Castro of the Atlantic Salmon Ecosystems Research Team for her input on this page.
Veteran intern Antonio Jones at an oyster farm in Drayton Harbor, Washington, checking traps for European Invasive Green Crab. Credit: Northwest Straits Commission
The Fishadelphia team. Credit: Dr. Talia Young.
