Atlantic Salmon

Common name: Atlantic Salmon, sea-run salmon, kelts, black salmon, “the leaper”, “king of fish”

 

Scientific name: Salmo salar 

 

Summary: The sea-run Atlantic Salmon used to be found in Maine’s rivers with great abundance. Unfortunately, the widespread construction of dams for milling and hydropower in the 1800s dramatically reduced their numbers alongside many other sea-run fish. For decades, dedicated groups have been working to bring Atlantic salmon back from the brink of extinction, and restore the legacy of “the leaper”. 

 

Classification: Atlantic salmon are members of the salmonid family, which also includes trout and char. 

 

Fun Fact: Landlocked salmon are the native 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. Originally, they were present only in West Grand Lake, Green Lake, Sebec Lake, and Sebago Lake. But beginning in the late 1860s, they were distributed throughout much of Maine, and today are found in more than 300 lakes.

 

Range: Atlantic salmon can be found on both sides of the Atlantic Ocean, including coastal rivers of northeastern North America, Iceland, Europe, and northwestern Russia. The species can be divided into three large groups (Baltic, European, and North American), which migrate through various portions of the North Atlantic Ocean. European and North American populations of Atlantic Salmon intermix during their at-sea stage, where they share similar summer feeding grounds off Greenland. The North American group historically ranged from northern Quebec southeast to Newfoundland and southwest to Long Island Sound. 

 

In the United States, Atlantic salmon were once native to almost every river north of the Hudson. Due to the effects of industrial and agricultural development (including habitat destruction, dams, and historic overfishing), most populations native to New England were eradicated. The present range of Atlantic salmon is much smaller, due to severely depleted populations. Currently, the only remaining wild populations of U.S. Atlantic salmon are found in rivers in central and eastern Maine, including the Dennys, East Machias, Machias, Pleasant,  Narraguagus, Cove Brook, Sheepscot, and Ducktrap rivers. These remaining populations comprise the Gulf of Maine distinct population segment (DPS), which was listed under the Endangered Species Act in 2000 and is genetically distinct from hatchery origin stock. 

 

Identification: Atlantic salmon have a spindle-like body shape—rounded, broad in the middle, and tapered at each end, and somewhat flattened toward the sides. The head is relatively small, about one-fifth of the body length, which may be up to 30 inches. The underside paired fins are prominent, especially on juveniles. Adult Atlantic salmon typically reach between 8 and 12 pounds, but may rarely reach upwards of 30 pounds.

 

Atlantic salmon change appearance throughout their life cycle to help them survive in different environments. While in freshwater, young Atlantic salmon have brown to bronze-colored bodies with dark vertical bars and red and black spots, which act as camouflage. These markings are colloquially known as “parr marks”. When young salmon migrate to the ocean, their parr marks disappear and they become silvery with nearly black backs and white bellies. When adults return to freshwater to spawn, they are very bright silver. After entering the river, they will again darken to a bronze color before spawning. After spawning, adults can darken further and are often referred to as black salmon. Once adults return to the ocean, they revert to their counter-shaded coloration dominated by silver.

 

Fun fact: Salmon scales are like tree rings, and can be used to identify how old a fish is, in addition to more complex metrics like how many years they spent in freshwater and saltwater, and how many times they have spawned. Scientists can also look at a salmon’s DNA using its scales, which can tell us things like if it has ever cross-bred with a farm raised fish.

 

Life history: Atlantic salmon have a complex life history and go through several stages that affect their behavior, appearance, and habitat needs. This complex anadromous life cycle involves transitioning between different environments, requiring significant physiological adaptations to survive in both freshwater and saltwater habitats. 

 

Atlantic salmon can have a lifespan of approximately 4-6 years. In Maine, they begin returning to their home rivers between March and November, with a peak migration during June and July. They spend a few months in cold, deep pools, and in the fall the females seek out gravelly areas with high levels of dissolved oxygen in which to build nests (redds) and lay their eggs. Larger salmon produce more eggs per pound of body weight, but on average she will lay around 7,500. Eggs incubate slowly due to the cold water temperatures, eventually hatching into alevin, with their yolk sac still attached. Alevins stay close to the redd for a few months hiding from predators in the spaces between gravel. During this stage they consume the yolk sac and grow in size. In the spring, once the yolk has been consumed, the alevin emerge from the redd and become fry. Fry develop spots on their sides for camouflage and begin to feed on their own. Only about 15 to 35 percent of eggs laid will survive to the fry stage.

 

As the water continues to warm, the fry grow into parr. Parr are typically 2-4 inches long and camouflaged with spots and vertical bars. The parr spend their time in freshwater nursery habitats, which are typically riffle areas with adequate cover, shallow water depth and moderate to fast water flow. They grow slowly for around 2 to 3 years until they are at least 6 inches long. Then, they start their out migration to the ocean– transforming into smolts and turning silver in the process. This physiological transformation is called smoltification and prepares the salmon for life in a saltwater marine environment. The cells in their gills must undergo chemical changes so they can tolerate saltwater, a process controlled by hormones and influenced by physical factors such as salinity, temperature, and light.

 

U.S. salmon leave Maine’s rivers as smolts in the spring and reach the seas off Newfoundland and Labrador by mid-summer. They spend their next 1-2 winters off the coast of Greenland, feeding on other fish and marine invertebrates and growing rapidly. However, before swimming back to their natal rivers to complete their spawning migration, the adults will stop eating altogether. Typically, an Atlantic salmon returning to U.S. waters will be 4 years old, having spent 2 years in freshwater and 2 years at sea. However, some salmon return after only one winter at sea, and are called grilse. Unlike the Pacific salmon species, Atlantic salmon do not necessarily die after spawning–a reproductive strategy known as iteroparity. These adults, called kelts or black salmon, return to the ocean to hopefully spawn again in future years–though repeat spawners are becoming increasingly rare.

 

Unfortunately, the reality is that only a tiny fraction of eggs live long enough to reproduce themselves. On average, only about 2 out of the roughly 7,500 eggs an adult female lays will live long enough to spawn as adults, which is another reason why repeat spawners are so valuable to the equation. 

 

Ecological importance: In many ways, salmon can be seen as indicators of overall ecosystem health. Salmon play an important role in many ecosystems, and are important for biodiversity. Due to their complex migratory lifecycle, salmon connect the food chains of freshwater and marine environments by bringing nutrients back and forth. They are a source of food for both marine and freshwater predators, and in turn prey upon a large variety of fish and invertebrates. The presence of salmon in a river can also indicate water quality and stream health, because they need specific conditions in order to thrive. The presence of cold refugia is especially important, because water that is too warm causes the fish to become so stressed they stop eating. 

 

Cultural importance: The hundreds of thousands of salmon that once filled Maine’s rivers each spring were an important source of food for indigenous tribes. After the arrival of European settlers, salmon became an important part of their diets as well. Alongside subsistence harvesting, Atlantic salmon have also supported social, cultural and economic relationships between communities for centuries. Throughout much of the 20th century, recreational anglers sought out opportunities to fish for salmon, coming from all over the state and country for a chance to catch a legendary fish. There’s a saying that goes “once you hook one, you’re hooked for life”. A handful of rivers in Maine, namely the Penobscot and Narraguagus, supported a salmon-centric tourism industry, which had its heyday between the 1950s and early 1980s. Watch the film “Salmon Country” to see footage of salmon fishing on the Narraguagus in the 50’s.

 

From 1912 to 1992, there was even a tradition known as the “Presidential Salmon”, where anglers competed annually to land the first (and largest) spring salmon and send it to the US President. The Presidential Salmon was born out of a Penobscot River competition when, in 1912, Karl Anderson sent his winning 22-pound salmon to President Taft. Even though salmon populations had been declining since the mid 1800s, the extent of their population decline wasn’t fully understood until later in the century. The tradition was finally suspended due to low salmon abundance in 1992, with President George H. W. Bush being the last president to receive a Penobscot river salmon.

 

Threats: Runs of Atlantic salmon are a scant fraction of their historic numbers, and the species was listed under the federal Endangered Species Act in 2000. They are currently unable to produce enough juveniles under natural conditions in the rivers to support their populations. 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. The main threats to the species are: 

 

Habitat degradation: Centuries of industrialization on New England rivers (e.g., paper and textile mills, deforestation of riparian areas and log drives) has resulted in the degradation of a lot of the fishes’ spawning and rearing habitat, effectively reducing the productive capacity of our rivers.

 

Barriers to migration: Barriers, such as dams and hydroelectric power plants, and poorly designed culverts at road crossings can delay or prevent juvenile salmon swimming downstream and adults swimming upstream. This can make it difficult or impossible for them to reach the habitats they need to survive.

 

Climate change: Fewer and fewer salmon survive their journey to and from the Northwest Atlantic, in part due to environmental stressors brought on by hotter, drier weather. Increasing water temperatures not only affect the fishes’ ability to find food, but also their ability to get sufficient oxygen, avoid disease, and compete with heat tolerant invasive predatory species like largemouth bass. 

 

Additional threats include interaction with escaped farmed fish that spread diseases, parasites, and dilute their genetics, continued harvest on declining populations, and pollution of our waterways, which impacts the fish both directly and indirectly.  

 

Conservation efforts: Dedicated individuals and organizations have been working for decades to bring Atlantic salmon back from the brink of extinction. Multiple restoration efforts by state and federal agencies, such as the Maine Department of Marine Resources, Bureau of Sea Run Fisheries and Habitat, and the National Marine Fisheries Service, build on a long history of salmon research and restoration. Wild fish are supported by a tremendous hatchery effort that stocks millions of juvenile salmon in Maine rivers every year. In addition to stocking, restoration efforts focus on improving habitat and water quality, and removing barriers to fish migration.

 

The Gulf of Maine Distinct Population Segment (DPS) of Atlantic Salmon is one of nine “Species in the Spotlight” selected to receive targeted efforts to halt declines and stabilize populations, through a program launched in 2015 by the National Marine Fisheries Service (NOAA Fisheries). This designation includes a recovery plan, which was most recently updated for the years 2021-2025. The key actions identified in this plan are to reconnect the Gulf of Maine with headwater streams by removing or retrofitting dams, improve the ability of freshwater habitats to produce fish capable of entering the marine environment, and to understand factors that contribute to decreased marine survival and mitigate them. 

 

Within the Gulf of Maine DPS are three Salmon Habitat Recovery Units (SHRUs), including the (Merrymeeting Bay, Penobscot Bay and Downeast Coastal SHRUs. Each of these local units has to meet certain recovery criteria before a down-listing or delisting decision can be made.

 

Habitat restoration: In 2016, the Penobscot River Restoration Project was completed, vastly improving access for Atlantic salmon and other sea-run fish to nearly 2,000 miles of their historic River. The project included removing the two lowermost dams (the Great Works dam in 2012 and the Veazie Dam in 2013), while adding a natural, stream-like bypass to the Howland Dam. To counteract the loss of those dams to produce hydropower, production was increased at upriver dams. Downeast Salmon Federation has also participated in dam removals in the Pleasant and East Machias rivers in the last few decades, and is currently helping organize the removal of the Nash-Stillwater dam, the last remaining barrier on the lower Narraguagus River. 

 

Stocking: Salmon have been stocked in Maine at least since the Craig Brook Hatchery in East Orland was designated a National Fish Hatchery in 1889. Juveniles are raised in hatcheries to various stages (i.e., fry, parr, and smolt) to supplement natural production in rivers and 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. Unfortunately, returns are still very low, with estimates ranging between 0.08-0.71%. 

 

Youth programs: Students across the region can participate in raising salmon through a citizen science and learning program called Fish Friends. This program, sponsored by the Atlantic Salmon Federation, allows classrooms to receive around 200 eyed eggs. Over the course of the late winter and early spring, students get to watch them grow into alevin and later, fry. Once the survivors reach the fry stage, the students are able to help release them into their natal river, with the hope that some will survive to adulthood. 

 

Fishery: There is currently no U.S. fishery for wild atlantic salmon, because the species is protected under the Endangered Species Act. However, there are still small recreational fisheries in Canada and Europe. Additionally, fishing is allowed in the US for landlocked salmon, the freshwater form of Salmo salar native to a handful of Maine lakes and stocked in many other lakes, rivers, and streams.

 

However, there is a long history of salmon fishing on both sides of the Atlantic. In Maine, indigenous tribes relied on salmon runs for food, as did European settlers after their arrival in North America. In 1880 alone, fishermen using weirs and gillnets caught more than 10,000 salmon in the Penobscot River, according to Ed Baum’s 1997 book “Maine Atlantic Salmon: A National Treasure.” Populations began to decline soon thereafter, but the commercial fishery in the Penobscot remained open until 1948. Fly fishing became popular in Maine rivers in the mid- to late-1800s. Anglers typically took hundreds of salmon in any year, but landings spiked around 1980. Between 1980 and 1986, anglers reported catching and keeping nearly 5,800 salmon in Maine rivers, according to Baum. The salmon fishery became catch-and-release only in 1995 and was closed altogether in 1999.

 

However, by far the biggest toll on Atlantic salmon populations was through commercial fishing at sea, off the coast of Greenland where the fish congregate in the winters. Commercial fishermen caught an estimated 1 million adult salmon off the coast of West Greenland annually in the 1970s plus an estimated 400,000 salmon off the coast of Canada.

 

Canada ended all commercial salmon fishing, except subsistence fishing for native tribes, in the 1990s. And after years of negotiations, commercial fishing off the coast of West Greenland was banned in 2002.

 

The North Atlantic Salmon Conservation Organization (NASCO) is an international body originally formed in 1984 to develop management measures for the distant-water fisheries at West Greenland and the Faroe Islands. This included the creation of a large protected zone free of targeted fisheries for Atlantic salmon in most areas beyond 12 nautical miles from the coasts. Further regulatory measures agreed by NASCO have greatly reduced the catch of salmon in the distant-water fisheries at West Greenland and around the Faroe Islands. There has been no commercial harvest by the Faroe Islands since the early 1990s and the Greenland fishery is currently an internal-use fishery.

 

Sources:

 

https://www.fisheries.noaa.gov/national/outreach-and-education/fun-facts-about-amazing-atlantic-salmon

https://www.fisheries.noaa.gov/species/atlantic-salmon

https://www.fws.gov/species/atlantic-salmon-salmo-salar

https://www.asf.ca/about-atlantic-salmon/

https://seagrant.umaine.edu/maine-seafood-guide/salmon/

https://www.nrcm.org/nrcm-creature-feature/atlantic-salmon/

https://nasco.int/atlantic-salmon/state-of-salmon/

https://www.maine.gov/dmr/fisheries/sea-run-fisheries/programs-and-projects/salmon-for-Maine-rivers

https://www.nrcm.org/news/200-years-of-troubled-waters-for-atlantic-salmon/