The common carp is one of the most abundant and widely distributed fish in Iowa. They were initially introduced into our waters from Europe more than a century ago, and since that time this fish has naturalized into nearly all waters. They occur in nearly every stream, river, man-made lake, and natural lake unless specific effort has been made to eliminate them. They are least common in coldwater streams and farm ponds.

Common carp is a large minnow, with the adults weighing up to 50 pounds or more. Its robust body is compressed laterally, and a soft, fleshy mouth opens ventrally. A stout, serrated, spinous ray at the leading edge of the dorsal and anal fins is a distinctive physical characteristic.

There are more than 16 soft rays in the dorsal fin (native cyprinids have less than 10) and from 4 to 6 soft rays in the anal fin. Pectoral fin soft ray counts range from 14 to 17, and pelvic fin soft ray counts vary from 8 to 9. A conspicuous barbel extends from the posterior corner of the upper jaw and a smaller, less conspicuous one is found along the side of the upper jaw. The lateral line is complete and may contain from 33 to 44 scales. Body scales are large, displaying a diamond-shaped appearance and have a black dot in the front of each scale. Body color is gray to olive dorsally, golden-yellow to bronzy-golden laterally, and yellowish-white ventrally. Pectoral, pelvic, and caudal fins are yellow to orange-red in adults. Young fish have a dusky vertical bar on the caudal peduncle which fades with increasing age. Pharyngeal teeth are broad and form three rows in the formula 1, 1, 3-3, 1. Molar-like grinding surfaces characterize the middle rows.

Common carp prefer warm water, either standing or with sluggish flow. They are most abundant in large rivers, man-made lakes and natural lakes where there is abundant, soft organic matter on the bottom. Carp adapt better than most fish species to pollution caused by sewage or agricultural run-off. They actually "thrive" in heavy effluent stretches and are very tolerant of turbid waters.

Carp are omnivorous feeders, taking both vegetable and animal matter in their diet. Aquatic insects, crustaceans, and small mollusks make up the bulk of their forage. They are particularly fond of tender roots and shoots of young aquatic plants and often "root-up" large quantities of vegetation and silt in their search for food. They are a nuisance in shallow, weedy habitat where their activity creates high turbidity in otherwise clear water. For this reason, carp have a limited use in nuisance aquatic vegetation control programs.

Spawning occurs from mid-April through June when the adhesive eggs are scattered in the shallow water over vegetation, debris, logs or rocks. Splashing carp, with their backs out of the water, may be observed in shallow waters during spring. Females can spawn more than 500,000 eggs over a period of several days, leaving several thousand at each spawning site.

Three varieties of common carp are found in Iowa. By far, the most abundant and widespread is the fully scaled specimen. Leather carp are scaleless, and mirror carp are covered with only a few large mis-shapen scales. Both leather and mirror carp are rare, and the former variety may have been extirpated because of its very unique genetic make up.

The reputation of carp has gone through an interesting transition since its North American introduction. Originally, its purpose was to furnish a fine food-fish to replace rapidly dwindling native fishes -- notably Eastern trout. Its easy adaptation to pond culture and high-quality protein were touted as major attributes. Carp were distributed widely across the United States by the U.S. Fish Commission during the latter part of the 19th century, but problems developed rapidly as carp escaped from pond culture and spread into other habitat -- soon distribution and stocking ceased.

Carp are able to dominate other fish species -- for two reasons. Carp, in their normal activities can change the aquatic habitat, and man has in many instances altered natural environments that favor carp.

This fish was viewed with disdain, and many eradication projects were undertaken in the early 1900`s through the 1960`s. Most projects failed to eliminate carp, and few showed improvements in native species populations. During this same time period, carp became a major commercial food-fish, being taken from the Great Border Rivers and natural lakes. Present annual harvest from the upper Mississippi River is over 5 million pounds, with over 2 l/2 million coming from Iowa waters. Iowa lakes presently provide about a million pounds of carp to commercial food-fish processors each year. Care is still exercised to prevent stocking of carp, and it is illegal to release this species into public waters. Eradication projects are still carried out for carp but usually only after other fish management efforts fail. Now the trend is toward carp utilization through commercial harvest and an increased awareness of sport and food potential of this naturalized species.

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*Mayhew, J. (editor). 1987. Iowa Fish and Fishing. Iowa Department of Natural Resources, Des Moines, Iowa. 323 pp.

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