American eel

Physical Description and Identification

The American eel possesses a long, slender, snake-like body covered in a thick layer of mucus, which gives it a naked and slimy appearance despite the presence of minute, embedded scales. Its dorsal and anal fins are continuous with a rudimentary tail fin, and it lacks pelvic fins entirely. Coloration is variable, ranging from olive green or brown on the back to a greenish-yellow on the sides, with a light gray or white belly. Individuals from clear water tend to be lighter than those from dark, tannic streams. Females are generally larger than males and have a lighter colour, smaller eyes, and higher fins. The scales are not arranged in overlapping rows but are irregularly distributed, sometimes resembling parquet flooring, and lie at right angles to each other. Unlike other bony fish, these scales develop long after the larval stage.

Distribution and Habitat in Canada

The American eel has a broad geographic range across eastern North America. In Canada, it is found in virtually any freshwater body, estuary, or coastal marine water connected to the Atlantic Ocean. Its range extends from the Atlantic coastline up the St. Lawrence River, into the Great Lakes, and inland through tributaries as far as Algonquin Park in Ontario. The species is highly adaptable and can be found in diverse habitats including streams, rivers, muddy or silt-bottomed lakes, coastal bays, and estuaries. Eels are bottom dwellers that hide during the day in burrows, under snags, or within masses of aquatic plants. They are remarkably mobile and can even climb small vertical barriers or move through wet grasses to access new habitats. During winter, eels burrow into mud and enter a state of torpor when water temperatures fall below 5 degrees Celsius, though they may occasionally remain active.

The Extraordinary Life Cycle

The life cycle of the American eel is a complex and lengthy journey defined by a semelparous and panmictic reproduction, meaning all individuals spawn once and then die, mixing in a single population in the Sargasso Sea. Adults make a final spawning migration from continental waters to the Sargasso Sea, where females can release up to 4 million, and sometimes as many as 8.5 million, buoyant eggs before perishing. The eggs hatch within a week into transparent, leaf-shaped larvae called leptocephali, which drift on ocean currents for 7 to 12 months before reaching the North American coast. Upon entering continental shelf waters, they metamorphose into transparent 'glass eels,' which then become pigmented 'elvers' as they move into estuaries and freshwater systems. The elver stage lasts three to twelve months and their movement inland is influenced by water temperature, flow, and tidal cycles. In freshwater, they develop into 'yellow eels,' a sexually immature stage where they feed and grow for 10 to 25 years. When they reach maturity, they undergo a 'silvering' metamorphosis, transforming into 'silver eels' with enlarged eyes and fins, a degenerated gut, and a greyish colour before migrating back to the Sargasso Sea to spawn.

Diet, Predation and Ecological Role

American eels are nocturnal, opportunistic benthic omnivores with a keen sense of smell. Their diet is extremely diverse and adapts to seasonal changes and local availability. They consume a wide variety of aquatic organisms including worms, insect larvae, crustaceans like crabs and crayfish, molluscs, small fish, fish eggs, frogs, and even plant matter or dead animal material. Studies show that smaller eels feed predominantly on aquatic insect larvae, while larger eels consume more fish and crayfish. A specific gastric study found that macroinvertebrates, especially insects like stoneflies, were eaten by 99 percent of feeding eels examined. As a top predator, the American eel helps control populations of other species. It also serves as a food source for many predators. Elvers and small yellow eels are prey for largemouth bass and striped bass, while larger eels are eaten by other fish, bald eagles, gulls, and other fish-eating birds. In a notable relationship, American eels constitute the entire diet of adult rainbow snakes, which are sometimes called eel moccasins.

Historic and Current Fishery

American eels were once an abundant species and a culturally and economically significant fishery for Indigenous peoples and later commercial operations. In Ontario, during the 1980s and early 1990s, it was one of the top three commercial species by value, with the Lake Ontario harvest valued at $600,000 and accounting for nearly half the value of the lake's total commercial fish harvest at its peak. However, commercial catches have plummeted from approximately 223,000 kilograms in the early 1980s to just 11,000 kg by 2002. In response to the severe decline, Ontario cancelled its commercial fishing quota in 2004 and closed the sport fishery. While the species remains part of a lucrative, and sometimes illegal, fishery in parts of Canada, management measures now include strict seasonal limits. For example, a bulletin specifies an open season from December 13, 2026, to February 16, 2027, for spearing only, with a minimum size limit of 20 cm. The primary market for American eel landings from the United States is the European Union.

Conservation Status and Primary Threats

The American eel is considered at very high risk of extinction in the wild by the International Union for Conservation of Nature and was assessed as Threatened by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) in 2012. In Ontario, populations have declined by more than 99%, and the vast numbers once present in the St. Lawrence and Ottawa Rivers have dwindled. The construction of hydroelectric dams is a primary threat, blocking migrations and causing local extirpations. The Ontario Ministry of Natural Resources estimates that 40 percent of mature eels are killed trying to pass through turbines. Other significant threats include past overfishing, habitat degradation, and pollution. Eels are sensitive to low dissolved oxygen levels often found below dams, and they bioaccumulate contaminants like heavy metals, dioxins, and PCBs in their fat tissues. While the U.S. Fish and Wildlife Service has twice determined that Endangered Species Act protection is not warranted, the species was under consideration for protection under Canada's Species at Risk Act as of August 2023. On December 2, 2025, the Government of Canada decided not to list the species, citing that the population's abundance across the country has remained stable over the past two decades.

Ongoing Recovery and Management Efforts

Conservation efforts for the American eel in Canada address several critical areas, with a major focus on reducing mortality at hydroelectric dams. Work is underway to improve fish passage on the St. Lawrence River and other waterways through the installation of eel ladders and similar structures. Scientists are researching innovative solutions, such as LED lights designed to guide eels away from dangerous turbine intakes. Advocacy groups, including the Canadian Wildlife Federation and Ontario Nature, emphasize the urgent need for the government to formally protect the eel's habitat, which has not been done despite its endangered status in Ontario. Community engagement and Indigenous-led initiatives, such as the Kiawerón:ko (American Eel) Symposium in Cornwall, Ontario, contribute to public awareness and collaborative management. In 2010, Greenpeace International added the American eel to its seafood red list to discourage consumption. Ongoing regulation of fisheries and habitat restoration in inland watersheds are considered necessary for the species' long-term recovery.

Interaction with Humans and Parks

The American eel features in public education and recreational activities within Canadian parks, highlighting its ecological importance. For instance, Liberty State Park hosted a free family-friendly event in May 2026 to explore the fascinating world of the American eel in the Hudson River context. Within national parks like Kouchibouguac, specific fishing regulations apply to protect aquatic life, including a daily catch limit of 10 fish during open seasons for all species. The estuaries in Kouchibouguac National Park host many fish and invertebrate species, including the American eel. The dramatic decline of the eel has made it a focal point for conservation messaging, with organizations using its story to illustrate the impacts of habitat loss and fragmentation. The species' unique biology and perilous status continue to make it a subject of scientific study and public interest across its range.

Questions about American eel

Where are American eels found in Canada?

American eels are found in a wide range of freshwater and coastal habitats across eastern Canada. They inhabit virtually any body of water connected to the Atlantic Ocean, including streams, rivers, lakes, estuaries, and coastal marine waters. Their range extends from the Atlantic coast up the St. Lawrence River into the Great Lakes, and inland through tributary systems as far as Algonquin Park in Ontario. They have also been historically present in the Ottawa River watershed. Non indigenous occurrences have been recorded in the past in places like Lake Mead, but these populations did not establish.

Why are American eel populations declining?

American eel populations have experienced severe declines, estimated at over 99% in parts of Ontario, due to several interconnected threats. The most significant cause of mortality is hydroelectric dams, which block migration routes and kill many eels in turbines. Past overfishing, both commercial and illegal, has also contributed greatly to the decline. Additional threats include habitat degradation, pollution, and the bioaccumulation of toxic contaminants like chlordane and polychlorinated biphenyls in their tissues, which reduces their health and reproductive success. The species is also very sensitive to low dissolved oxygen levels commonly found below dams.

Where do American eels spawn?

All American eels spawn in the Sargasso Sea, a region of the North Atlantic Ocean. This is where their life cycle begins and ends. After spending 10 to 25 years growing in continental freshwater habitats, mature eels undergo a final transformation and migrate thousands of kilometres back to this specific area to spawn. The females release millions of eggs there before dying, and the resulting larvae then drift on ocean currents back toward North American coasts. The discovery of the spawning location was detailed by scientist Marie Poland Fish in 1926.

Is it legal to fish for American eel in Canada?

Fishing regulations for American eel are strict and vary by province due to conservation concerns. In Ontario, the commercial fishery quota was cancelled in 2004 and the sport fishery is closed. In some jurisdictions, highly regulated seasons exist, such as a spearing-only season from December 13, 2026, to February 16, 2027, with a daily catch limit and a minimum size restriction of 20 cm. It is crucial to check current local regulations, as rules are subject to change to protect the species. Violations of fishing regulations in national parks can lead to prosecution under the Canada National Parks Act.

What is being done to help American eels recover?

Recovery efforts focus on reducing mortality at hydroelectric dams by constructing eel ladders and other passage facilities to allow safe upstream and downstream migration. Research into deterrents, like LED lights to guide eels away from turbines, is ongoing. Conservation organizations advocate for stronger government action, including the legal protection of eel habitat. There are also community and Indigenous-led educational initiatives, such as the Kiawerón:ko Symposium, aimed at raising awareness and promoting collaborative stewardship of the species. The government of Canada continues to monitor the population, having decided against a Species at Risk Act listing in late 2025.

Are American eels protected under Canadian law?

The American eel was assessed as Threatened by COSEWIC in 2012 and was under consideration for listing under the federal Species at Risk Act. However, on December 2, 2025, the Government of Canada decided not to add the American eel to the legal registry, concluding that the population's abundance across Canada has remained stable over the previous two decades. The species remains endangered under Ontario's provincial Endangered Species Act, though its critical habitat has not yet been formally protected by regulation. The U.S. Fish and Wildlife Service has also twice declined to list the species under the Endangered Species Act.

Sources: Wikipedia and current public reporting, checked by the Your Space Hamilton desk. Last updated 2026-10-22.