American eel

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The American eel is a snake-like fish living along the Atlantic coast of North America. The color of these eels depends on their habitat and their stage in life. Individuals living in muddier waters are normally darker than those living in clear water. Adults are usually brown or olive green with yellow sides and a light underside. The young American eels, depending on their stage in life, can be clear, gray, or yellow. The dorsal and anal fins of these fish form one continual fin along the fish’s back. As with all other fish, the American eel has scales, but their scales are so small that their skin feels very smooth. American eels also have mucous covering their skin making them very difficult to hold. These fish have very small eyes and their jaw extends past these eyes. In general, eels are nocturnal.

Size

Female American eels are much larger than males. While the males grow up to two feet (60 cm) long, the females sometimes reach up to five feet (152 cm) in length! Females weigh up to 16.5 pounds (7.5 kg), while the weight for males is not known.

Diet

American eels are opportunistic predators, meaning they will eat almost any animal that they can. Such prey include fish, crayfish, snails, insects, and frogs. Some American eels may even eat carrion.

Habitat

American eels live in both freshwater and marine habitats depending on their stage of life. Most of the time is spent in freshwater where streams, rivers, and lakes are home to American eels. Some of these fish also live in estuaries, places where fresh and salt water meet. Because American eels are nocturnal and most other animals in their habitat are diurnal, these animals need a place to hide during the day to avoid being eaten. Hiding places include beside logs and rocks, in deep pools, among vegetation, and under mud or sand.

Threats

In recent years, the American eel population has been declining. One of the main threats to these fish is dams blocking their migration path. Even if obstacles do not block the eel from getting to its destination, they may cause the animal stress, making it more susceptible to predators. The main predators of these animals include catfish and predatory birds. Pollution is also a form of death for some American eels. A parasite called the Asian swimbladder nematode is known to infect the swim bladders of American eels, making it harder for them to migrate. American eels are commercially fished, and while most people would not find an eel appetizing, Europeans consider it somewhat of a delicacy. Seaweed harvest in the Atlantic ocean may affect these animals’ spawning habits.

Status and conservation

The IUCN has not assessed the status of the American eel, but this fish is protected in the Ontario Endangered Species Act. In 2004, a petition was filed to the United States Fish and Wildlife Service to list this animal as an endangered species. As of 2015, the petition is still under review.

Regulations are being enforced to restrict fishing gear in order to help protect american eels. Other activities to protect these animals include making paths around dams in order to allow the eels to move freely.

Mating, eggs, and young

American eels are catadromous, meaning they live mostly in freshwater but migrate to saltwater to breed. They are the only catadromous fish in North America. American eel spawning occurs in the fall, and large females can release up to 30 million eggs! These eggs are then fertilized by the males. After hatching, the transparent young float around in the Atlantic ocean currents for around one year before they reach the coast. Once the young eels reach the length of about 2.5 inches (6.5 cm), they transform into their first juvenile phase. A few weeks after entering fresh water, the young eels enter their next phase and are called elvers. During this stage they eat a lot more than in the first one and therefore grow a lot faster. Elvers are greenish-brown in color. Females migrate far inland, but males normally stay close to the meeting place of salt and fresh water. In the wild, these animals can live up to 50 years, while in captivity one individual lived for 86 years!

Overcoming obstacles

Waterfalls and dams would pose an almost impossible challenge for most migrating fish, but American eels have two ways of sometimes getting around these obstacles. First of all, if the obstructive surface is damp and textured, these eels (especially the elvers) can climb over the obstacle even if it is vertical! If this trick does not work, the eels can sometimes swim out of the water and wriggle around the obstacle. Most fish would suffocate doing this, but american eels can absorb oxygen through their skin as well as through their gills.

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Sources:

Photo credits:

  • American eel – Cliff
  • Mystery animal – Brian.gratwicke

One Response

  1. Charis Dwire
    Charis Dwire at |

    Could it be a fire-bellied toad?

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