How to Tell a Carp From a Sucker Fish

sucker and carpAlthough carp and suckers are freshwater fish species that have some similarities, they belong to separate families of fishes. The common carp, a fish not native to North America but found across the continent after its introduction from overseas, is from the Cypranidae family. Suckers are part of the Catostomidae family. Telling these types of fish apart requires knowing their main differences. (Pictured left: Bluehead sucker; Pictured right: carp)


Difficulty: Moderately Easy

Step 1
Estimate the weight and lengths of carps and suckers that you see. The carp has a "robust" body, according to the Pennsylvania Fish and Boat Commission website, with an arching back. The common carp and other carp species can weigh in excess of 50 lbs. in some instances and can be 30 inches long. In contrast, suckers are smaller and have a more elongated, tubular shape than carp. Sucker species, such as the northern hog sucker, are considered large if they weigh 4 lbs. and measure 2 feet long.
Step 2
Observe the mouths of the carp and the sucker. The carp has a forward-facing mouth, whereas suckers have a ventral mouth possessing thick lips, designed to vacuum food from the bottom of its aquatic habitat. Neither type of fish has teeth in its mouth. Their teeth are in their throat.
Step 3
Look at the barbels on the sides of a common carp's mouth. Common carp have these fleshy protrusions of soft tissue on each side, which help them detect food in the water. Suckers lack barbels.
Step 4
Count the number of membrane supports, known as rays, in the top fin of carps and suckers to distinguish them from each other. The common carp will have anywhere from 17 to 21 rays. Suckers will have fewer. For example, the northern hog sucker has 11 dorsal fin rays, and the white sucker has between 10 and 13. Both suckers and carp have soft and flexible rays, but carps have a harder ray that will seem like a spine at the beginning of the fin.
Step 5
Study the habitat in which you find or catch a fish that you think may be a carp or sucker. Carp can live in a wide array of ecosystems, such as lakes, ponds, rivers, streams and sloughs. The "National Audubon Society Field Guide to Fishes" notes carp can live in clear, muddy and even polluted waters. While some suckers also live in parts of the same places as carp, carp will be in the slowest sections of flowing water, while suckers normally reside in the faster moving sections.

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