Grass carp (Ctenopharyngodon idella)

Grass carp caught in the St. Croix River.
Grass carp caught in the St. Croix River.

Species and Origin: The grass carp, or white amur, is a very large fish in the minnow family (Cyprinidae). The body is torpedo shaped with moderately large scales, while the head has no scales. They are silver to olive in color. The adults consume aquatic plants and can weigh up to 70 pounds. It is native to southeastern Russia and northwestern China and was brought to Arkansas in the 1960s to control aquatic plants in reservoirs and aquaculture farms.

Impacts: Their herbivorous feeding can dramatically reduce aquatic vegetation and they can harm water quality by increasing phosphorus levels.

Status: Wild populations of these fish exist in many waters of the United States. No populations are known to be in Minnesota, although individual fish have been caught in state border waters such as the Mississippi River below the Twin Cities and Okamanpeedan Lake on the Minnesota-Iowa border. In 2006, a commercial fisherman caught a large grass carp in the St. Croix River (see photo). See US map  .

Means of spread: They have been stocked in waters of other states, escaped or spread to other waters in flood events, and have spread throughout connected river systems.

Where to look: They have a strong preference for densely vegetated inshore areas of backwaters of large rivers, ponds, and lakes 3 to 10 feet in depth.

Regulatory Classification: It is a prohibited invasive species (DNR), which means import, possession, transport, and introduction into the wild is prohibited.

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Further information:
Carp identification: Keys , Fish Invaders of the Great Lakes