Grass Carp

Ctenopharyngodon idella

Native to eastern Asia, the grass carp, Ctenopharyngodon idella, is a large herbivorous fish in the minnow and carp family. It has a long, torpedo-shaped body, a blunt head, large scales, and powerful pharyngeal teeth that grind plant material. Young fish eat some small invertebrates, but adults are chiefly associated with submerged aquatic vegetation. That appetite explains their use in ponds, canals, reservoirs, and irrigation systems, as well as the concern when they establish outside managed waters.

For pond owners and water managers, grass carp are a biological tool rather than aquarium fish; mature individuals can exceed a meter in length and need large, oxygenated water bodies. Stocking should be planned carefully because they may remove desirable cover for fish and wildlife as readily as nuisance weeds. Many regions allow only certified triploid, functionally sterile fish, and permits or barriers may be required to prevent escape. Good management includes matching numbers to the vegetation problem, monitoring water quality as plants are eaten, and avoiding release into natural waterways.