The Grass Carp are also called White Amur, belongs to the minnow family. A name developed and used to avoid the negative connotations of “carp.” This large import from China is primarily a freshwater herbivore introduced for aquatic weed control. In many parts of the country it is considered an invasive species and stocking/transporting it is illegal. However, it is still stocked for to control weeds, typically as sterile, triploid fish. The process to create sterility is not usually 100% effective, so the young are usually tested for triploidy before being sold.
Amur have a torpedo shaped body with moderately large scales. The head is scaleless. Coloring ranges from silver to olive in color on the back, shading to white on the belly. Its mouth is terminal, no barbells, with non-fleshy, firm lips. The dorsal fin has 8 to 10 soft rays. Anal fins are closer to the tail than most other minnows.
In its native habitat, Grass Carp are fish of large, turbid rivers and associated floodplains. They have a wide degree of temperature tolerance. Spawn at occurs at temperatures 68 to 86 degrees Fahrenheit. As these minnows spawn in flowing water and do not reproduce well in lakes and ponds. Reproductive success requires an adequate flow of oxygen rich water. Wild populations do exist in many waters of the United States.
Juvenile grass carp rely primarily on phytoplankton for food, but have been reported to eat small invertebrates and crustaceans. Adults feed primarily on aquatic vegetation, consuming up to three times their weight in food each day. Grass carp are rapid growers, with fish stocked at eight inches in the spring reaching 18 inches by fall. Adults can obtain sizes in excess of four feet and fifty pounds. They are known to exceed one hundred pounds in China.
Grass Carp in Texas
Ctenopharyngodon and idella are both Greek words, meaning "comb-like throat-teeth" and "distinct" respectively. The grass carp is one of the largest members of the minnow family. The body is oblong with moderately large scales, while the head has no scales. There are three simple and seven branched rays on the dorsal fin. Grass carp are silvery to olive in color, lacking the golden hue of common carp, and they have no barbels. This species typically reaches sizes of 65 to 80 pounds in its native habitat, but individuals approaching 400 pounds have been reported.
Typically, spawning occurs in the spring when water temperatures reach 59-63°F, and under rising water conditions. Eggs are semi-pelagic and must remain suspended during the 20-40 hour incubation period. Therefore, long river stretches are usually necessary for successful spawning. Once young grass carp reach approximately three inches in length, they become nearly 100% herbivorous. Their feeding habits make them ideal as vegetation control agents, as they are capable of consuming 40% to 300% of their body weight per day in plant material. The species shows a high tolerance for salinity; specimens have been known to survive for several days in water up to three times as salty as sea water.
Grass carp are potentially harmful to native resources. Currently, only triploid (sterile) grass carp are legal for use in Texas, and a permit is required to obtain them. Because grass carp is a potentially invasive species, an angler who catches one must immediately remove the intestines, except in waters where a valid Triploid Grass Carp Permit is in effect. In those waters, any grass carp caught must be immediately returned to the water unharmed. The herbivorous feeding habits of this species make it very difficult to catch. When landed, grass carp are excellent table fare despite their bones. The rod-and-reel record in Texas stands at 53.5 pounds. A specimen in excess of 69 pounds was landed by a bow fisher.
Courtesy of Texas Parks and Wildlife