Grass carp are legal to stock in Oklahoma without a permit, but some states require sterile triploid fish or outlaw grass carp completely. Although, usually classified as an opportunistic feeder, grass carp aggressively feed on vegetation. Grass carp activity and growth is greatly reduced when water temperature drops below 57 degrees F. These fish prefer soft vegetation but consume tougher plant species as preferred food supplies diminish. Grass carp readily consume pelleted fish rations when available. In natural habitat, adult grass carp are found in back waters of large river systems in Asia.
Aquatic vegetation is abundant and provides both food supply and cover from predators.
Spawning is determined primarily by photoperiod or day length and water temperature. The fish begin to spawn when flood waters swell rivers, water temperature reaches 70-75 degrees F. and photoperiod is increasing above eight hours of daylight per day. Mature adults form schools and swim upstream for many miles into the swift flowing waters found in upper reaches of the river. The grass carp spawn, releasing semi-buoyant, nonadhesive eggs which are fertilized as they float downstream. Eggs moving downstream are oxygenated and hatch into fry after an incubation period of 24-28 hours.