The size and shape of characins (CARE-uh-suhns) vary widely. Some species are quite small, and one is quite large. Most characins are silvery, but some are brightly colored. Most characins have an adipose (AE-dih-POS) fin, a short fin between the dorsal (DOOR-suhl) fin, which is the fin along the midline of the back, and the tail fin. The anal (AY-nuhl) fin, the fin along the midline of the belly, may be short or long, with as many as forty-five rays. Characins have a set of bones that connect the swim bladder, an internal sac used to control position in the water, with the inner ear.
Characins inhabit all types of freshwater, including weedy river edges, still ponds, rushing streams, and even underground caves.
Most characins eat fish. Some eat invertebrates (in-VER-teh-brehts), or animals that lack a backbone. Some eat only plants, fruits, and seeds. Some eat plankton, very small microscopic (MY-kro-SKA-pihk) plants and animals drifting in the water. Some feed on waste material, mud, and algae (AL-jee), tiny plantlike growths that live in water and have no true roots, stems, or leaves. Some eat the scales or pieces of fins of other fishes.
BEHAVIOR AND REPRODUCTION
Some characins form schools when they are young but become solitary (SA-le-TER-ee) and travel alone as adults. Some travel in large groups during all life stages. When injured by a predator (PREH-duh-ter), or an animal that hunts and kills other animals for food, characins release a substance that warns others in the school to escape. Most characins scatter their eggs into the water and do not tend the eggs or the young, but some build nests.
CHARACINS AND PEOPLE
Many characins are popular aquarium fishes. Others are important as food. Some are popular for sport fishing.
Piranhas in groups of twenty to thirty wait in plants to ambush prey. They attack the prey in a feeding frenzy intensified by the presence of blood in the water. Piranhas are not likely to attack humans unless the person is bleeding or in water near groups of prey animals.
The World Conservation Union (IUCN) lists one characin as Endangered, or facing a very high risk of extinction in the wild in the near future.
Physical characteristics: Giant tigerfish are the largest characins, reaching a length of 4 feet, 4 inches (1.3 meters) and a weight of 110 pounds (50 kilograms). The fully scaled body is pointed at the ends and has a high dorsal fin. The body is silvery, and the back is darker gray. The fins are often orange or red, and the fish may become brightly colored during the breeding season. The teeth are sharp, and the upper teeth interlock with the lower teeth.
Geographic range: Giant tigerfish live in Africa.
Habitat: Giant tigerfish live in large rivers and near the shores of lakes.
Diet: Adult giant tigerfish are fierce predators that consume a variety of smaller fish. The larvae (LAR-vee), the early stage that must change form before becoming an adult, eat animal plankton, but they quickly move to larger prey as they grow.
Behavior and reproduction: Giant tigerfish gather with other giant tigerfish of similar size. Small fish make large groups, and large fish make small groups. In the summer these fish migrate (MY-grayt) or move in rivers to find a place to spawn or release their eggs along the shores of lakes or the flooded banks of large rivers. Females scatter hundreds of thousands of eggs into plants, where they hatch. The adults give no parental care.
Giant tigerfish and people: Giant tigerfish attract fishermen from around the world. They also are used for food by people who live in their geographic range.
Conservation status: Giant tigerfish are not threatened or endangered. ∎
Physical characteristics: Red-bellied piranhas have an average length of 6 to 8 inches (15 to 20 centimeters) but can grow to 12 inches (30 centimeters). The belly, the throat, the pectoral (PECKter-uhl) fins, or the front pair, the pelvic fins, or the rear pair, and the anal fins are bright red. The sides are often pale brown to slightly olive, and the back is bluish gray to brownish. The powerful jaws have sharp, triangular, interlocking teeth.
Geographic range: Red-bellied piranhas live in South America.
Habitat: Red-bellied piranhas live in creeks and ponds. They prefer areas with dense plant life.
Diet: Red-bellied piranhas eat other fishes but also scavenge for food and eat insects, snails, worms, and plants.
Behavior and reproduction: Red-bellied piranhas look for food mainly at dusk and dawn. After a courtship display involving swimming in circles, the female deposits layers of eggs on plants in the water, and the male fertilizes them. The male guards the egg masses and fans them with his fins until the eggs hatch in nine or ten days.
Red-bellied piranhas and people: Red-bellied piranhas are kept as aquarium fish. This activity is illegal in some parts of the United States to prevent irresponsible hobbyists from releasing the piranhas into the wild, where they can multiply and prey on native fishes. People who live along the rivers inhabited by red-bellied piranhas catch and eat them.
Conservation status: Red-bellied piranhas are not threatened or endangered. ∎
Physical characteristics: River hatchetfish are about 1 to 2 inches (3.8 centimeters) long. The deep body is very narrow from side to side. The belly looks like a semicircle from the side, and the chest muscles are large. The pectoral fins are long and high on the body near the head. These fish are yellow to silver with a dark stripe running along the length of the body. The fins are clear.
Geographic range: River hatchetfish live in South America.
Habitat: River hatchetfish live near the surface of slow water in creeks and swamps.
Diet: River hatchetfish eat worms, crustaceans (krus-TAY-shuns), or water-dwelling animals that have jointed legs and a hard shell but no backbone, and insects on the surface of the water but also capture flying insects.
Behavior and reproduction: River hatchetfish live in groups near the surface of the water. They can be aggressive or calm. To avoid predators and capture insect prey, these fish swim very fast to rise out of the water, then fly above the surface using their long pectoral fins. River hatchetfish spawn after a lengthy courtship. The female scatters eggs in the water or onto floating plants, and the male fertilizes them. The eggs then fall to the bottom or onto plants.
River hatchetfish and people: River hatchetfish are common in aquariums.
Conservation status: River hatchetfish are not threatened or endangered. ∎
FOR MORE INFORMATION
Berra, T. M. Freshwater Fish Distribution. San Diego: Academic Press, 2001.
"Characiformes." All Science Fair Projects. http://www.all-science-fair-projects.com/science_fair_projects_encyclopedia/Characiformes. (accessed on September 25, 2004).
Weldon, Ryan. "Piranha." WhoZoo. http://www.whozoo.org/Anlife99/ryanweld/piranhaindexfinal.htm (accessed on September 25, 2004).