Description
From Scott and Crossman (1973), Jester (1974), and Pflieger (1975): adult length 12-25 in (30.5-63.5 cm) or more; large individuals may reach 20-60 lbs (9.1-27.2 kg); two barbels on each side of upper jaw, posterior pair more conspicuous; relatively small, toothless mouth, with the upper jaw slightly protruding; throat teeth 1,1,3-3,1,1, with teeth in main row broad and molar-like; lateral line complete, with 35 to 38 scales; one long dorsal fin with 17-21 soft rays, and a stout saw-toothed spine in front of dorsal and anal fins; pectoral fins with 14-17 rays; pelvic fins thoracic, originating beneath origin of dorsal fin, 8 or 9 rays; 1 anal fin with 5 branched rays; scales cycloid, large, thick; 35-36 vertebrae; 21-27 gill rakers on first gill arch; color variable: back and sides olivaceous, gold, greenish-olive, reddish-brown, or blackish-red, silver or yellowish-white below; fins dusky, often with red on tail fin and yellow or orange on lower fins; peritoneum gray, often more or less speckled.
Habitat
Usually occurs in rivers, lakes, ponds, reservoirs, swamps, or low-salinity estuaries; usually in shallow water with abundant vegetation and little or no current; generally does not inhabit first-order, cold streams or deep lakes with little or no littoral zone. Tolerant of wide range in oxygen, salinity, turbidity, and bottom conditions. Fry, juveniles, and adults tolerate temperatures between 5 and 35 C; optimal growth occurs between 25 and 30 C (Edwards and Twomey 1982). Carp can live in water with turbidities in excess of 200 JTU and secchi disc visibilities less than 8 cm (3.2 in) (Jester 1974). A pH level greater than 10.5 or less than 5.0 is harmful (Edwards and Twomey 1982). Air gulping occurs when dissolved oxygen (DO) level is less than 0.5 mg/l; 6-7 mg/l DO is needed for optimum growth (Edwards and Twomey 1982). Some carp occur in areas with water currents as swift as 120 cm/sec, but much slower waters are preferred, such as less than 20 cm/sec in the Missouri River (Edwards and Twomey 1982).
Optimal river habitat is characterized by warm water (above 20 degrees C during the growing season, about mid-June through August), low gradient (above 1.5 m/km), shallow vegetated marshland available for spawning, at least 50% of the river area in pools or off-channel areas, adequate cover (logs, brush, etc.) in pools, and fertile conditions.
Optimal lake habitat has warm water (as defined above), at least 25% littoral area, aquatic or inundated vegetation for spawning, deeper waters for overwintering, and fertile conditions (Edwards and Twomey 1982). In winter, carp may occur in deeper water than used in summer. In Lake Winnebago, Wisconsin, adults spent the summer in 3-4 ft (0.9-1.2 m) of water and moved to 4-8 ft (1.2-2.4 m) in the winter (Otis and Weber 1982). Carp spent the winter in 5-7 m of water in Lake Mendota, Wisconsin (Johnson and Hasler 1977).
Usually, carp spawn in shallows and flooded areas in water depths of less than 0.5 m, but spawning has been observed in 1.8 m deep water (Edwards and Twomey 1982). Eggs are scattered and stick to submerged objects. Carp fry stay attached to the vegetation for about two days before dropping to the bottom, and they inhabit shallow (less than 2 m), warm sluggish water during their first summer (Edwards and Twomey 1982).
Ecology
Carp have well-defined home ranges in both summer and winter but do not use the same ranges from season to season or from year to year (Otis and Weber 1982). In Wisconsin, winter home ranges, were one-third the size of summer ranges, and most of the everyday activities occurred in an area encompassing about 45% of the home range (Otis and Weber 1982).
Extensive movements sometimes occur. In a mark-recapture study in Missouri, 51.3% of the carp were recaptured within 1 mile of their release site and 90% stayed within 25 miles, but one individual was recaptured over 200 miles away (Funk 1955). In a Wisconsin lake, most anchor-tagged carp were recaptured within 2 miles of their release site, but one carp moved 7.5 miles (12.1 km) in 18 days and one was recaptured 19.5 miles (31.4 km) away after 72 days (Otis and Weber 1982). A carp tagged near Columbia, Missouri, was recaptured 28 months later in South Dakota, a distance of 676 stream miles (1090 km) (Pflieger 1975).
Adult carp have few enemies except humans; some juveniles are prey for predatory fishes, birds, and mammals. Sometimes, in shallow lakes and ponds, large numbers are killed by severe winter conditions (Shields 1957, Jessen and Kuehn 1958, Threinen 1949). Large-scale destruction of eggs occurs when water levels drop after the major spring spawning period, exposing and desiccating millions of eggs (Shields 1957, Sigler 1958).
Reproduction
Spawning occurs in spring and summer. Optimal water temperature for spawning is 18-22 C, although spawning can occur at water temperatures of 16-26 C (Shields 1957, Sigler 1958, Swee and McCrimmon 1966, Jester 1974). In South Dakota, a combination of rapidly rising water levels that inundated spawning areas and water temperatures above 62 F (16.5 C) were the primary stimulants for spawning (Shields 1957). Carp spawn from April through early August in Wisconsin (Miller 1952), mid-May through early August in Ontario (Swee and McCrimmon 1966), and late March through early fall in Missouri (Pflieger 1975) and New Mexico (Jester 1974).
The spawning act begins by the segregation of carp into small groups of 4-20 individuals, led by a large female. With their backs and dorsal fins sticking above the water, the female broadcasts her eggs while swimming and splashing and several males release milt into the water. The sticky eggs adhere to plants, logs, and rocks and harden in 15-25 minutes. In Ontario, 90% of the eggs attached to vegetation were fertile (Swee and McCrimmon 1966). The average number of eggs per female in New Mexico is 47,134 (Jester 1974) and 902,942 in Ontario (Swee and McCrimmon 1966). There is a direct relationship between the number of eggs produced and the length (and age) of the female. Very large (19.1-23.3 lbs, 8.7-10.1 kg) and old (16-18 years) females can produce 1-2 million eggs (Swee and McCrimmon 1966, Jester 1974). Many females retain as much as 20% of their eggs for a second spawn, and males spawn with several females throughout the season (Swee and McCrimmon 1966).
The eggs hatch in 3-16 days, depending on the water temperature, and the newly hatched fry are approximately 3 mm long (Swee and McCrimmon 1966).
The age of sexual maturity varies with water temperature. Males become sexually mature at 2-3 years in Wisconsin, South Dakota, and New Mexico, and at 3-4 years in Ontario (Threinen 1949, Shields 1957, Swee and McCrimmon 1966, Jester 1974). Females mature approximately one year later.
In Elephant Butte Lake, New Mexico, carp had an average life span of 1.3 years (Jester 1974). The maximum lifespan for males appears to be 8-10 years and 16-18 years for females (Swee and McCrimmon 1966, Jester 1974).