BOWFINS: Amiiformes

PHYSICAL CHARACTERISTICS

Bowfins have a long, curved dorsal (DOOR-suhl) fin, the one that runs along the top of the body. These fishes are called living fossils (FAH-suhls) because they have existed in the same form for more than one hundred million years. The skeleton is made up of both bone and cartilage (KAR-teh-lej), or tough, bendable supporting tissue. The tail fin is short and rounded. Bowfins have a large bony plate between their lower jawbones, and bony plates cover the skull.

GEOGRAPHIC RANGE

Bowfins live only in eastern North America.

HABITAT

Bowfins live in freshwater in lakes and slow-moving rivers that have a large amount of plant life.

DIET

Bowfins are predators (PREH-duh-ters) with huge appetites. Predators are animals that hunt and kill other animals for food.

BEHAVIOR AND REPRODUCTION

Bowfins are very strong. They can stand high temperatures and breathe air at the surface if necessary. They spawn, or release eggs, the female reproductive cells, in the springtime.

BOWFINS AND PEOPLE

Bowfins are not used for food or sport.

CONSERVATION STATUS

Bowfins are not threatened or endangered.

BOWFIN (Amia calva): SPECIES ACCOUNT

Physical characteristics: The long, curved dorsal fin of a bowfin has forty-two to fifty-three rays, or supporting rods, inside. Bowfins reach a length of about 35 inches (89 centimeters) but are usually shorter. The world-record bowfin weighed almost 22 pounds (10 kilograms), but the usual weight is 2 to 5 pounds (0.9 to 2.5 kilograms). Males are smaller than females. The long, thick body of bowfins is dark olive green on top, lighter on the sides, and cream to greenish yellow on the bottom. The tails of males have a dark spot rimmed in orange. Females also have a dark spot, but it is not rimmed in orange. Other names for bowfins are blackfish, cottonfish, cypress trout, freshwater dogfish, grindle, grinnell, marshfish, mudfish, scaled ling, and speckled cat.

Geographic range: Bowfins live only in eastern North America. Their range includes the Saint Lawrence River system, which extends from the eastern part of the United States and Canada to the Great Lakes, and the Mississippi River system, which extends from Minnesota to Texas and Florida.

Habitat: Bowfins live in swampy, sluggish water in warm lakes and rivers that have a great deal of plant life. Because they can breathe surface air, bowfins can live in water too polluted and stagnant, or still and stale, for other fishes.

Diet: Bowfins are greedy predators. Young bowfins feed on small animals such as insect adults and larvae (LAR-vee), or insects at a young stage of life before becoming adults, and plankton, or microscopic plants and animals drifting in the water. Once bowfins grow to a length more than about 4 inches (10 centimeters), they eat other fishes. Adults also eat crayfish, shrimp, insect adults and larvae, frogs, and plants. Bowfins are sluggish and clumsy and stalk prey, or animals used for food, by scent as much as by sight. Bowfins capture their prey with sudden gulps of water.

Behavior and reproduction: Bowfins have gills, special organs for obtaining oxygen from water, but they also use their swim bladder, or an internal sac usually used for controlling position in the water, for breathing surface air. Male bowfins move into shallow waters of lakes and rivers to prepare a round nest hidden by plants or under a log. Once a female, and sometimes more than one, is attracted into the nest, she lays as many as sixty-four thousand eggs in four or five batches. The male then fertilizes (FUR-teh-lye-sez) the eggs, or deposits sperm, which unites with the eggs to begin development. The young hatch in eight to ten days and use a sticky organ on the tip of the snout, or nose area, to attach themselves to plants or other objects on the bottom. After seven to nine days, the young form a tight, sphere-shaped school that is guarded by the male for several weeks. After the school breaks up, bowfins move back into deep water.

Bowfins and people: Bowfins are often considered pest fishes because they compete for food with sport fishes. People seeking other fishes sometimes catch bowfins, but they usually let them go because bowfin does not taste good. Bowfins are important predators in some regions, because they control populations of unwanted fishes and keep populations of game fishes from becoming too large, which would stunt the growth of the individual fishes.

Conservation status: Bowfins are not threatened or endangered. ∎

FOR MORE INFORMATION

Books:

Gilbert, Carter Rowell, and James D. Williams. National Audubon Society Field Guide to Fishes: North America. New York: Knopf, 2002.

Ricciuti, Edward R. Fish. Woodbridge, CT: Blackbirch, 1993.

Schultz, Ken. Ken Schultz's Field Guide to Freshwater Fish. New York: Wiley, 2004.

Web sites:

Paulson, Nicole, and Jay T. Hatch. "Bowfin Amia calva (Linnaeus, 1766)." Minnesota Department of Natural Resources' MinnAqua Aquatic Program. http://www.gen.umn.edu/research/fish/fishes/bowfin.html (accessed on September 2, 2004).