Amia calva
Beaverfish
(Also: Blackfish; Bonnetmouth; Bowfin; Cottonfish; Cypress trout; Freshwater dogfish; Grindle; Grinnel; John A. Grindle; Lawyer; Marshfish; Scaled ling; Speckled cat; Western mudfish)

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)

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)

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)

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)

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)

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)

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)

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)

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)

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)

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)

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)

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)

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)

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)

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)