Montana Field Guide

Common carp are easily recognized by the two barbels or "whiskers" on each side of the mouth, golden-brown coloration and the "saw-toothed" hardened ray in the front of the dorsal and anal fins. The introduction of carp into North America from Asia is considered to be one of the greatest mistakes in the history of American fisheries management by biologists who have documented the widespread loss of native fish and habitat to this aggressive intruder. Carp are a popular food fish in Eurasia, so they were introduced into North America to serve the same function. However, they are not desirable to North American consumers because they are bony, often have an unpalatable taste and because there are more attractive alternatives. There is some commercial fishing for carp, and they can be processed so that the problems with the fine bones between their muscles are eliminated. Carp are also despised because they compete with more desirable sport fishes, muddy the water by their bottom feeding, and reduce the available food for waterfowl by eating submerged plants. They are extremely hardy omnivores, which means that they eat almost anything. Carp can attain a weight of 40 pounds in productive waters. In Montana, carp are widespread in our eastern drainages. They attain their greatest numbers in lakes and reservoirs.

Overall bronze with a dark brown to olive green back and yellowish underside. Some individuals, called mirror carp, have enlarged scales scattered over the body with bare patches in between. Leather carp are scaleless. 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.

May migrate into tributary streams in the summers to spawn.

Primarily lakes and reservoirs, where it seeks moderately warm water and shallows. Also rivers, where it prefers pools and backwaters. Congregates in areas of organic enrichment, such as sewage outfalls. Tolerates turbid water and low dissolved oxygen; avoids cold and swift, rocky streams. (Holton 2003) Spawns in shallow weedy areas (Brown 1971).

An omnivorous feeder with vegetation and detritus making up bulk of diet. May feed on any available aquatic organism including eggs of sportfish. Larval common carp feeds primarily on zooplankton. In its native range, juveniles and adults feed on benthic organisms (e.g., chironomids, gastropods and other larval insects), vegetation, detritus and plankton (e.g., cladocerans, copepods, amphipods, mysids). Feeding habits are similar in the U.S., where the diet is composed of organic detritus (primarily of plant origin), chironomids, small crustaceans, and gastropods (Summerfelt et al. 1971; Eder and Carlson 1977; Panek 1987). Will stir up bottom and cause muddied waters while feeding (Gould, personal communication, Brown 1971).

In the U.S., the common carp is more abundant in manmade impoundments, lakes, and turbid sluggish streams receiving sewage or agricultural runoff, and less abundant in clear waters or streams with a high gradient (Pflieger 1975; Trautman 1981; Ross 2001; Boschung and Mayden 2004). Young of year carp in Missouri River Study showed a preference for pool and backwater habitat. Considered ecological disaster in North America. The common carp is regarded as a pest fish because of its widespread abundance and because of its tendency to destroy vegetation and increase water turbidity by dislodging plants and rooting around in the substrate, causing a deterioration of habitat for species requiring vegetation and clean water (Cahoon 1953). May reproduce with goldfish causing hybrids. Schools in large numbers multiplying the effects of the destruction on habitats.

Sexually mature in 2-3 yrs. Spawns May-July in most Montana waters. Incubation: 12-20 days (Brown 1971). Spawned mid- June-July in middle Missouri River with late June-early July peak.

Carp have been the target of large eradication projects in several states that have generally only temporarily reduced populations. Stocked ponds with outlets to nearby rivers can be poisoned to prevent their unintentional spread. Once established in a water body, common carp is difficult and expensive to eliminate (e.g., Cahoon 1953). DeVaney et al. (2009) performed ecological niche modeling to examine the invasion potential for common carp and three other invasive cyprinids (grass carp Ctenopharyngodon idella, black carp Mylopharyngodon piceus, and tench Tinca tinca). The majority of the areas where common carp have been collected, stocked, or have become established had a high predicted ecological suitability for this species.

Contact information for Aquatic Invasive Species personnel:
Montana Fish, Wildlife, and Parks Aquatic Invasive Species staff
Montana Department of Natural Resources and Conservation's Aquatic Invasive Species Grant Program
Montana Invasive Species Council (MISC)
Upper Columbia Conservation Commission (UC3)

Tolerates turbid water and low dissolved oxygen; avoids cold and swift, rocky streams. (Holton 2003). So, higher flows and colder water temperatures are a limiting factor for further spread in western Montana. Although, warming rivers with carp populations on the east side of the divide may cause carp to further expand their distribution upstream.