Eels and Morays: Anguilliformes
EELS AND MORAYS: Anguilliformes
Eels and morays have long, thin bodies. The color ranges from black or dark gray for eels and morays that live in the deep sea to rich colors and complex patterns in those that inhabit tropical reefs. The length ranges from about 4 inches (10 centimeters) to 13 feet (4 meters). Most eels and morays do not have scales, or thin, hard plates covering the skin. Eels and morays have as many as seven hundred vertebrae (ver-teh-BREE), the bones that make up the spinal column.
Eels and morays live all over the world.
Eels and morays live in streams, lakes, estuaries (EHS-chew-air-eez), deep-sea waters, and coral reefs. Some spend most of their lives in freshwater and then move to the sea to spawn, or produce and release eggs. Some live in open water, but most live in small openings in coral reefs and rocks or burrow in the soft bottom.
Eels and morays eat almost any animal available, from insects to fishes. Some eels and morays feed on dead animals that lie on the ocean bottom, including whales.
BEHAVIOR AND REPRODUCTION
Eels and morays migrate (MY-grayt), or move from one place to another, for spawning. They swim by means of wavy side-to-side movements of the body and fins. They also can swim backward, which allows them to retreat rapidly into their burrows when threatened.
Eels and morays use external fertilization (FUR-teh-lih-zay-shun), or the joining of egg and sperm outside the body to start development. The eggs hatch into long (2 to 4 inches, or 5 to 10 centimeters), flat, clear, filmy larvae (LAR-vee) with sharp, fanglike teeth. The larvae can be found at varying depths, from the surface of the ocean to 1,640 feet (500 meters). The larvae undergo metamorphosis (meh-tuh-MOR-pho-sus), the changes in form that some animals make to become adults, in the open ocean six months to three years after hatching. The colder the water, the longer is the larval stage. Young eels and morays, or elvers, use ocean currents to reach the habitat they will live in as adults. They then grow and mature for as long as ten years.
EELS, MORAYS, AND PEOPLE
Freshwater eels are valued as food. Some morays and conger eels are popular in public and home aquariums.
A KNOTTY SITUATION
Some eels tear apart prey by tying themselves into knots to obtain leverage against the prey. The eel grabs, often by the head, a fish that is too large to swallow whole. Then the eel turns its tail back toward its body and forms a series of loops that make a knot similar to a square knot or a figure-eight knot. The knotting continues until the heads of the eel and the prey are against the knotted eel's body. The eel then pulls its own head through the knot and, with it, a mouthful of food. This action usually rips the head off the prey fish. The eel then bites onto another section of the prey, and the process continues.
Eels and morays are not threatened or endangered.
Physical characteristics: American eels have snakelike bodies covered with thick slime. Males grow to 5 feet (1.5 meters) and females to 4 feet (1.2 meters). These eels weigh as much as 16 pounds (7 kilograms). American eels have 103 to 111 vertebrae.
Habitat: At sea American eels live in deep water. In freshwater they live in streams with constant flow.
Diet: The larvae of American eels eat plankton, which are microscopic plants and animals drifting in the water. Elvers eat water insects; small crustaceans (krus-TAY-shuns), or water-dwelling animals that have jointed legs and a hard shell but no backbone; and dead fish. Adults eat insects, crustaceans, clams, worms, fish, frogs, toads, and dead animals.
Behavior and reproduction: While in freshwater, American eels hide during the day. At night they swim near the bottom in search of food. Not much is known about reproduction among American eels. During autumn adults migrate to the western part of the Atlantic Ocean for spawning, which takes place in January. The females lay up to four million buoyant eggs, or eggs that can float on the water, and then die. After fertilizing (FUR-teh-lye-zing) the eggs, the males also die. The larvae drift toward coastal waters for as long as eighteen months. They then transform into elvers. American eels spend most of their lives, as long as twenty years, in freshwater before returning to the sea for spawning.
American eels and people: American eels are consumed as food.
Conservation status: American eels are not threatened or endangered. ∎
Physical characteristics: Green morays grow to 8 feet (2.4 meters) in length and weigh as much as 64 pounds (29 kilograms). Green morays are green to dark grayish green all over. The green color comes from the combination of yellow slime on dark blue skin.
Geographic range: Green morays live throughout the western and eastern Atlantic and the eastern Pacific Oceans.
Habitat: Green morays live at the bottom along rocky shorelines, in reefs, and among mangrove trees in waters shallower than about 98 feet (30 meters).
Diet: Green morays eat fishes and bottom-dwelling crustaceans.
Behavior and reproduction: Green morays attach themselves to coral or rocks or bury themselves in the bottom and allow the front half of their bodies to move with the current, keeping their mouths open to catch any food animal that comes near. Green morays are cleaned by small fishes. Little is known about reproduction among green morays except that they use external fertilization and have clear, fanged larvae.
Green morays and people: Green morays are consumed as food. Large ones can cause food poisoning, however.
Conservation status: Green morays are not threatened or endangered. ∎
Physical characteristics: Slender giant morays are the longest of the eels and morays, reaching 13 feet (4 meters). These morays are brownish gray on top and paler on the bottom.
Geographic range: Slender giant morays live in the western Pacific and Indian Oceans.
Habitat: Slender giant morays live on the muddy bottoms of coastal waters, including bays and rivers.
Diet: Slender giant morays eat crustaceans and fishes.
Behavior and reproduction: The most interesting habit of slender giant morays is that they stand straight up and down from their burrows with the head beneath the surface, rising and falling with the tide. Almost nothing is known about their reproduction.
Slender giant morays and people: Slender giant moray is a food fish.
Conservation status: Slender giant morays are not threatened or endangered. ∎
FOR MORE INFORMATION
Schultz, Ken. Ken Schultz's Field Guide to Freshwater Fish. New York: Wiley, 2004.
Schultz, Ken. Ken Schultz's Field Guide to Saltwater Fish. New York: Wiley, 2004.
"American Eel." Chesapeake Bay Program. http://www.chesapeakebay.net/info/american_eel.cfm (accessed on September 14, 2004).
"Fish in Focus: Green Moray Gymnothorax prasinus (Richardson, 1848)." Australian Museum Fish Site. http://www.amonline.net.au/fishes/students/focus/gymno.htm (accessed on September 14, 2004).