American eel facts for kids
Quick facts for kids American eel |
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| Conservation status | |
| Scientific classification | |
| Genus: |
Anguilla
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| Species: |
rostrata
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| Range map | |
| Synonyms | |
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Leptocephalus grassii |
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The American eel (Anguilla rostrata) is a special type of fish found along the eastern coast of North America. These eels live in fresh water and estuaries, which are places where rivers meet the sea. But they leave these homes to travel to the Atlantic Ocean to lay their eggs.
American eels have a long, snake-like body. It's covered in a layer of mucus, which makes them look smooth and slippery. They actually have tiny scales, but they are hard to see. A long dorsal fin runs along their back and connects to a similar fin on their belly. They don't have pelvic fins, but they do have small pectoral fins near their head. Their color can change, from olive green or brown to yellowish-green and light gray on their belly. Eels from clear water are often lighter than those from darker rivers.
These eels hunt mostly at night. During the day, they hide in mud, sand, or gravel close to the shore. They eat small crustaceans, aquatic insects, and other small water creatures they can find.
American eels are important for fishing in some areas. People use them as bait to catch other fish like striped bass. In some places, people also eat them. Young eels, called glass eels, are sometimes caught for aquaculture, which is like farming fish. However, this is now limited in many areas to protect the eels.
Eels used to be very common in rivers. They were an important food source for aboriginal people. But building hydroelectric dams has blocked their journeys. This has caused eel numbers to drop in many rivers, like the St. Lawrence and Ottawa Rivers in Canada.
Contents
What's in a Name?
The American eel, Anguilla rostrata, was first described in 1817 by Lesueur. The word Anguilla is Latin for "eel." The word rostrata is a Latin word that can mean "beaked or curved" or "long nose."
Appearance and Features
American eels can grow to be about 4 feet (1.22 meters) long. They can weigh up to 16.5 pounds (7.5 kg). Female eels are usually larger than males. They also tend to be lighter in color, with smaller eyes and bigger fins.
Their body is long and looks like a snake. The fins on their back and belly connect to their small tail fin. They don't have fins on their underside, but they do have fins near their gills. They have a clear line along their side called a lateral line, which helps them sense things in the water. Their head is long and cone-shaped, with small, well-developed eyes. Their mouth is at the end of their snout, and their jaws are not very long. They have tiny teeth in several rows.
Their scales are very small and hard to see without a magnifying glass. They are not arranged in neat, overlapping rows like on many other fish. Instead, they are scattered in an irregular pattern. The first scales don't grow until much later in the eel's life, not right after they hatch.
Scientists can tell American eels apart from other eel species. They look at the total number of bones in their spine, the number of muscle segments, and the distance between their dorsal fin and their anus. These features stay the same from when they are tiny larvae to when they are grown-up eels.
Where They Live
Geographic Range
American eels live in many different places. You can find them in fresh water like streams and lakes, in estuaries, and in coastal ocean waters. Their natural home stretches along the eastern Atlantic Ocean coast. This includes areas from Venezuela all the way up to Greenland and Iceland. Inland, they can be found in the Great Lakes and the Mississippi River.
Sometimes, American eels have been found in places they don't naturally live. For example, they were seen in Lake Mead on the Colorado River. They were also put into Sacramento and San Francisco bays in California a long time ago. However, they didn't seem to survive in those places. They were also accidentally introduced or stocked in other states like Illinois and Ohio.
Natural Habitat
Eels like to live at the bottom of the water. They hide in burrows, tubes, or among plants and other shelters. You can find them in many different habitats. This includes streams, rivers, and lakes with muddy bottoms during their freshwater stage. They also live in ocean waters, coastal bays, and estuaries.
Eels can move between fresh, salt, and brackish (a mix of fresh and salt) water. They spend different amounts of time in each. In winter, when temperatures drop below 41°F (5°C), eels burrow into the mud. They become very inactive, almost like sleeping. However, they might still move around a little during this time. Eels can handle a wide range of temperatures. Young eels can even survive in temperatures as low as 30.6°F (-0.8°C).
Eels move around during different seasons. In spring, they travel from fresh water to estuaries and coastal bays to feed. In the fall, young eels might return to fresh water to spend the winter. Older eels, called silver eels, will migrate south to the Sargasso Sea to lay their eggs. Eels are very good at moving around. They can even use small streams or move through wet grass to reach new places. Small eels can climb over barriers. However, things like pollution, dams, and turbines can make it harder for them to find good homes or can even kill them.
Life Cycle of the American Eel
The American eel has a very interesting and complex life cycle. It all begins far out in the Sargasso Sea. This is a special part of the Atlantic Ocean. Young eels then float with ocean currents. They eventually travel inland into streams, rivers, and lakes. This journey can take many years, with some eels traveling up to 3,700 miles (6,000 kilometers)! After reaching these freshwater homes, they eat and grow for about 10 to 25 years. Then, they migrate all the way back to the Sargasso Sea to lay their eggs and complete their life cycle.
Here are the different stages of their life:
- Eggs:
The eggs hatch within about a week in the Sargasso Sea. Female eels can lay between 500,000 and 4 million eggs. Very large eels can even lay up to 8.5 million eggs! The eggs are about 1.1 mm wide. The eggs are fertilized outside the body. Adult eels are thought to die after laying their eggs. No adult eels have ever been seen migrating back up rivers after spawning.
- Leptocephali:
This is the larval form of the eel. It looks very different from the adult eel. Leptocephali are clear, flat, and look like a leaf. They have a small, pointed head and large teeth. These tiny larvae are carried by ocean currents, like the Gulf Stream, towards the eastern coast of North America. This journey can take 7 to 12 months. They usually stay in the top 1,150 feet (350 meters) of the ocean. They grow about 0.008 to 0.015 inches (0.21 to 0.38 mm) each day.
- Glass Eel:
As the leptocephali get closer to the coast, they change into glass eels. These young eels are transparent and have the typical long, snake-like shape of an eel. The term "glass eel" refers to all stages from the end of the larval change until they get their full color. This change happens when they are about 2.2 to 2.6 inches (55 to 65 mm) long. They use the tides to help them move up estuaries. At this stage, they change from living in the open ocean to living on the bottom near the coast.
- Elvers:
Glass eels start to get their color as they move closer to shore. At this point, they are called elvers. This coloring happens when the young eels are in coastal waters. At this stage, it's still not possible to tell if they are male or female. The elver stage lasts about three to twelve months. Elvers that enter fresh water may spend a lot of this time swimming upstream. Their arrival is linked to warmer temperatures and lower water flow early in the migration season. Later, it's influenced by the tides.
- Yellow Eels:
This is the stage where the eels are sexually immature adults. They start to turn yellow with a creamy or yellowish belly. At this stage, they are still mostly active at night. Eels that stay in estuaries tend to complete their life cycle faster than those that travel into fresh water. However, eels in fresh water often live longer and grow much larger. Whether an eel becomes male or female depends a lot on its environment. Scientists think that if there are many eels in one place, more males will be produced.
- Silver Eels:
As the yellow eel gets ready to reproduce, it changes into a silver eel. This "silvering" change prepares the eel for its long journey back to the Sargasso Sea. The eel turns grayish with a white or cream belly. Their digestive system shrinks, their pectoral fins get bigger for better swimming, and their eyes get larger to see better in the ocean. Their skin gets thicker, and they store more fat for energy during their migration and spawning. Their reproductive organs also develop.
What Do Eels Eat?
Eels are active at night, so they do most of their eating then. They have a very good sense of smell and likely use it to find food. American eels are not picky eaters. They live in many different places, so their diet is very varied. They eat most aquatic animals that live in the same environment.
Leptocephali
Scientists don't know much about what tiny leptocephali eat. Some studies suggest they don't eat tiny animals called zooplankton. Instead, they might eat tiny bits of dead material in the ocean, like "marine snow" or waste from other creatures.
Glass Eels and Elvers
Early studies suggested that glass eels couldn't eat. However, later research found that elvers, which are a more developed stage, do eat. When scientists looked inside the stomachs of elvers caught migrating upstream, they found that they mainly ate insect larvae.
Yellow Eels
Yellow eels are mostly active at night and eat things from the bottom of the water. Their diet includes fish, clams, snails, crabs, insect larvae, insects from the water surface, worms, frogs, and even plants. Eels prefer small prey that they can easily catch. What they eat changes with their size. Smaller eels (less than 16 inches or 40 cm) in streams mostly eat aquatic insect larvae. Larger eels eat more fish and crayfish. Eels also change their diet with the seasons and what's available around them. They eat less or stop eating in winter. They also stop eating when they are getting ready to migrate to spawn.
Who Eats Eels?
Not much information has been published about what animals eat eels. It's known that young elvers and small yellow eels are eaten by fish like largemouth bass and striped bass. However, eels are not a main part of these predators' diets. Leptocephali, glass eels, elvers, and small yellow eels are probably eaten by various fish that hunt other fish. Older eels are also known to eat younger glass eels. Other animals that eat eels include other types of eels, bald eagles, gulls, and other birds that eat fish.
Eels and Fishing
Most of the yellow and silver eels caught in the US are sold to countries in Europe.
In the 1970s, about 125,418 kg of eels were caught each year in the North Atlantic. This was worth about $84,000. In 1977, Maine, New Hampshire, and Massachusetts caught a lot of eels. Maine caught about 79,700 kg, New Hampshire caught 2,700 kg, and Massachusetts caught 143,300 kg. These catches were worth a lot of money.
In the 1980s and early 1990s, the American eel was one of the top three most valuable fish for fishing in Ontario, Canada. At its best, the eel catch was worth $600,000. In some years, eels made up almost half of the total value of all commercial fish caught in Lake Ontario. However, the amount of American eels caught has dropped a lot. It went from about 223,000 kg in the early 1980s to only 11,000 kg in 2002.
Protecting the American Eel
The International Union for the Conservation of Nature says that the American eel is at a very high risk of disappearing from the wild.
The number of American eels and the amount caught by fishing have dropped a lot. This has raised concerns about the future of this species. For example, the number of young eels in the Lake Ontario area fell from 935,000 in 1985 to about 8,000 in 1993. By 2001, the number was almost zero. Fast declines were also seen in Virginia and in parts of Canada.
Because their life cycle is so complex, eels face many threats. Some threats are specific to certain stages of their life. Since they travel to the ocean to lay eggs, they need to be able to swim downstream freely. They also need many different types of habitats to grow and mature.
The number of male and female eels can also be affected. This is because males and females often use different habitats. Problems in certain areas can greatly impact how many males or females there are.
Even though American eels can live in many temperatures and salt levels, they are very sensitive to low oxygen levels. These low levels are often found below dams. Pollution from heavy metals, dioxins, and other chemicals can build up in the eels' fat. This can make them sick and reduce their ability to reproduce. This is a big problem because eels have a lot of fat.
Building dams and other water facilities reduces the number and variety of homes for eels. Digging in rivers can affect their migration, how they are spread out, and what food is available. Too much fishing, especially catching too many young eels, can also harm local populations.
Other natural threats include competition with new species like the flathead catfish and blue catfish. Diseases, parasites, and changes in ocean currents can also affect them. These changes can alter how larvae are carried and how young eels migrate back to fresh water.
Conservation Efforts
The U.S. Fish and Wildlife Service has looked at the American eel's status twice, in 2007 and 2015. Both times, they decided that the eel did not need protection under the Endangered Species Act.
In Canada, the province of Ontario stopped commercial fishing for eels in 2004. Fishing for eels as a sport has also been closed. Efforts have been made to help eels pass hydroelectric dams on the St. Lawrence River.
Sustainable Eating
In 2010, Greenpeace International added the American eel to its "seafood red list." This list includes fish that are often sold in stores but are at a very high risk of being caught in ways that are not good for the environment or the species.
- Froese, Rainer, and Daniel Pauly, eds. (2005). "Anguilla rostrata" in FishBase. 10 2005 version.
See also
In Spanish: Anguila americana para niños
