Amia calvaBeaverfish(Also: Blackfish; Bonnetmouth; Cottonfish; Cypress trout)

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Geographic Range

Bowfin are found as far north as the upper St. Lawrence River in Quebec and Ontario, and as far south as Southern Texas and Florida. They can be found from the east coast and west into South Dakota, Nebraska, Missouri, Kansas, and Central Oklahoma (Scott and Crossman, 1973). (Scott and Crossman, 1973)

Habitat

Bowfin live in backwater pools of rivers, lakes, and swamps. During times of high water, bowfin swim into river cutoffs and ther floodplain habitats. Often times they are trapped here when the water level decreases. Due to their ability to breath air they can survive in these drained ponds for relatively long periods of time. There have been reports of bowfin surviving for 21 days buried in the mud of a drained pond (Ross, 2001). Bowfin also inhabit ditches, pits and pools of slow streams. Theses streams are small projections of mainly the Mississippi (and subsidiaries), and the St. Lawrence River. Bowfin prefer generally clear water with large amounts of aquatic vegetation (Scott and Crossman, 1973). (Ross, 2001; Scott and Crossman, 1973)

  • Aquatic Biomes
  • lakes and ponds
  • rivers and streams

Physical Description

Amia calva are most easily recognized by two distingushing features. The first is a very large gular plate located on the ventral side of the head, between the mandibles. This plate is unique among fishes that live within the bowfin's geographic range (Trautman, 1957). The second distingushing feature is a very long dorsal fin. The fin has 46-50 soft rays and covers approximately 42.7-47.5% of total body length. Amia calva have paired pelvic fins located ventrally at mid-body. The anal fin is composed of 9-10 soft rays and is located ventrally at the midpoint of the dorsal fin. Bowfin have large, rounded pectoral fins composed of 16-19 soft rays and located relatively low on the body. The body itself is long and cylindrical in shape. Bowfin are laterally compressed, but have a body depth of 14.2-19.7% of total length. This gives the bowfin a long stout look. Bowfin are dark olive with lighter coloration on the sides and a cream colored belly. They typically have a vertical barred pattern on the sides, a horizontal barred pattern on the dorsal fin, and an irregular vertical barred pattern on the caudal fin. Adult males have a prominent black spot with a yellow to orange halo on the caudal fin. In females, the orange/yellow is absent (Scott and Crossman, 1973). (Scott and Crossman, 1973; Trautman, 1957)

  • Sexual Dimorphism
  • female larger
  • male more colorful
  • Range mass
    9750 (high) g
    343.61 (high) oz
  • Average mass
    900-1360 g
    oz
  • Range length
    109 (high) cm
    42.91 (high) in
  • Average length
    45-61 cm
    in

Development

Bowfin eggs hatch 8-10 days after fertilization, and are approximately 8 mm long at this time. The young are tadpole-like with a body deflected by a yolk sac (Ross, 2001). The hatchlings have an adhesive organ on the tip of their snout that attaches them to the nest. They remain in the nest for an additional 7-10 days. Over this period they grow from 8 mm to 10-13 mm and the yolk sac is absorbed into the body (Ross, 2001). The immature fish grow quickly. They reach 5-9 inches (12.5 to 22.5 cm) in length over a period of four to six months. Individuals reach sexual maturity after a period of 3-5 years, or when a certain length is reached (18 inches (45 cm) = male, 24 inches (60 cm) = female) (Scott and Crossman, 1973). (Ross, 2001; Scott and Crossman, 1973)

Reproduction

During mating (springtime) males and females alike move into spawning areas. These areas are shallow, vegetated waters in lakes or ponds. Females often lay eggs in several nests, and as a result, males often have eggs from more than one female in their nest (Scott and Crossman, 1973). (Scott and Crossman, 1973)

Bowfin mate once a year during the springtime. In the south, spawning can occur in late April, but in most cases it occurs in late May and early June. The male bowfin prepares a nest in shallow, vegetated waters. The nest is simply a clearing in the vegetation made by biting off roots. A slight depression is made so the eggs won’t be swept away. A female lies on the bottom of the nest while the male circles her. They lie side by side and flap their fins. The female releases her eggs and the male releases his milt (sperm). More than one female can lay her eggs in a male’s nest, and females often lay eggs in several nests. It is common that there are eggs in different developmental stages in a single nest. The male guards his nest very aggressivly. There are often as many as three times more males than females in a spawning ground, which can lead to conflict (Scott Crossman, 1973). (Scott and Crossman, 1973)

  • Breeding interval
    Bowfin breed once yearly
  • Breeding season
    Late April-Early June
  • Average time to hatching
    8-10 days
  • Average age at sexual or reproductive maturity (female)
    3-5 years
  • Average age at sexual or reproductive maturity (female)
    Sex: female
    1551 days
    AnAge
  • Average age at sexual or reproductive maturity (male)
    3-5 years
  • Average age at sexual or reproductive maturity (male)
    Sex: male
    1460 days
    AnAge

The male takes care of all the parental investment duties. After fertilization the male guards the nest and keeps the eggs supplied with fresh water by moving his pectoral fins. Males may be so aggressive they will attack inanimate objects such as sticks, and have been known to leap out of the water toward invaders on the waters edge near the nest (Ross, 2001). When the hatchlings begin to swim the male guards them as well. The juveniles swim in schools guarded by the male until they reach four inches in length. At this time the young bowfin begin the solitary behavior of adults (Richmond, 1997). (Richmond, 1997; Ross, 2001)

  • Parental Investment
  • pre-hatching/birth
    • provisioning
      • male
    • protecting
      • male
  • pre-weaning/fledging
    • protecting
      • male
  • pre-independence
    • protecting
      • male

Lifespan/Longevity

Bowfin do not normally live longer than 12 years in the wild. Average age varies depending on specific area, but is normally 10-12 years. Ages up to 30 years have been reported for bowfin in captivity (Ross, 2001). (Ross, 2001)

Behavior

Amia calva are a very aggressive predatory species. They are solitary and spend most of their time searching for prey. Bowfin stay in deeper waters during the day, and move into shallower waters at night (Scott and Crossman, 1973). (Scott and Crossman, 1973)

Communication and Perception

Bowfin have been described by Scott and Crossman (1973) as “…a slow, clumsy, stalking predator that uses scent as much as sight…” (Scott and Crossman, 1973)

Food Habits

Amia calva is a non-specific predator. This can be seen by the variety of foods they consume. Though they eat most anything, the largest percent of their food is made up of insects, fishes, crustaceans, and amphibians. Some common examples include frogs, bass, other bowfin, dragonflies, sunfish, crayfish, etc (“Bowfin”, 1995). Bowfin use their forward movement and suction to catch their prey. Bowfin take approximately .075 seconds to open and close their mouth, and it is this quick motion that creates the suction bowfin rely on for food (Ross, 2001). ("Bowfin", 1995; Ross, 2001)

  • Animal Foods
  • amphibians
  • reptiles
  • fish
  • carrion
  • insects
  • mollusks
  • aquatic crustaceans

Predation

Adult bowfin are rarely eaten by other organisms. In studies of bowfin diet, other bowfin were found in the stomach contents (Scott and Crossman, 1973). Another study showed that in Florida, bowfin were a source of food for alligators (Delany, Linda, and Moore, 1999). (Delany, et al., 1999; Scott and Crossman, 1973)

Ecosystem Roles

Amia calva are voracious predators. Bowfin are very near the top of the food chain in most of the ecosystems they inhabit, and as a result they eat most everything else. In areas in which bowfin are relatively abundant, they make a significant impact on the populations of their prey fish (Ross, 2001). (Ross, 2001)

Economic Importance for Humans: Positive

Though bowfin are not a "game fish", many anglers enjoy catching this animal. They are not sought after for their meat due to its pasty consistency, but are exciting to catch do to their aggressive behavior and strong bodies (Scott and Crossman, 1973). Bowfin eggs have been marketed fairly successfully as a less expensive caviar under the name "Choupiquet Royal" (Ross, 2001). (Ross, 2001; Scott and Crossman, 1973)

  • Positive Impacts
  • food

Economic Importance for Humans: Negative

Amia calva are voracious eaters and can have a negative impact on game fish in the area. Since the majority of a bowfin’s diet is composed of other fish such as bass and bluegill, they can have negative effects on the populations of these animals (Scott and Crossman, 1973). (Scott and Crossman, 1973)

Conservation Status

Though Amia calva is not listed as threatened or endangered it is considered a candidate species that could achieve the threatened or endangered level. The main methods to stop A. calva from reaching this level are to develop, maintain, and protect wetlands, as well as controlling sedimentation. ("Bowfin", 1995)

Other Comments

C. Linnaeus first described Amia calva in 1766 (Eschmeyer, 2004). They are the only species left in the family Amiidae as all the other genera are long extinct (Scott and Crossman, 1973). Bowfin are primitive air-breathing fish that often go to the surface to gulp air. They have a highly vascularized lung that extends the length of the body cavity. The gills are also modified so that they will not collapse when exposed to air. Their gill lamellae are fused so the tips are always held apart, preventing collapse when not supported by water (Ross, 2001). (Eschmeyer, 2004; Ross, 2001; Scott and Crossman, 1973)

Contributors

Adam Emerson (author), University of Michigan-Ann Arbor, William Fink (editor, instructor), University of Michigan-Ann Arbor.

Renee Sherman Mulcrone (editor).

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

carrion

flesh of dead animals.

chemical

uses smells or other chemicals to communicate

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

external fertilization

fertilization takes place outside the female's body

fertilization

union of egg and spermatozoan

food

A substance that provides both nutrients and energy to a living thing.

freshwater

mainly lives in water that is not salty.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

insectivore

An animal that eats mainly insects or spiders.

keystone species

a species whose presence or absence strongly affects populations of other species in that area such that the extirpation of the keystone species in an area will result in the ultimate extirpation of many more species in that area (Example: sea otter).

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

piscivore

an animal that mainly eats fish

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

visual

uses sight to communicate

References

Pennsylvania Game Commission. Bowfin. PA010009. NA: Species Information Library. 1995. Accessed October 20, 2004 at http://biblioline.nisc.com.proxy.lib.umich.edu/scripts/login.dll?BiblioLine&dbname=QSIL.

Ashley, K., R. Rachels. 1999. Food Habits of Bowfin in the Black and Lumber Rivers, North Carolina. Conference of Southeastern Associattion of Fish and Wildlife Agencies, 1: 50-60. Accessed October 25, 2004 at http://md1.csa.com/htbin/ids65/procskel.cgi.

Delany, M., S. Linda, C. Moore. 1999. Diet and Condition of American Alligators in 4 Florida Lakes. Conference of the Southeastern Association of Fish and Wildlife Agencies, 1: 375-389. Accessed October 25, 2004 at http://ca1.csa.com.proxy.lib.umich.edu/htbin/ids65/procskel.cgi.

Eschmeyer, W. 2004. "Amia Calva" (On-line). Fishbase. Accessed October 25, 2004 at http://www.fishbase.org/Summary/SpeciesSummary.cfm?ID=2600&genusname=Amia&speciesname=calva.

Richmond, A. 1997. "Bowfin or Dog Fish" (On-line). Accessed October 25, 2004 at http://www.bio.umass.edu/biology/conn.river/bowfin.html.

Ross, S. 2001. Inland Fishes of Mississippi. Mississippi: University Press of Mississippi.

Scott, W., E. Crossman. 1973. Freshwater Fishes of Canada. Canada: Bryandt Press Limited.

Trautman, M. 1957. The fishes of Ohio. Baltimore, Maryland: The Ohio State University Press.