A Brief History of The Grass Carp
White amur or grass carp are a quick growing, plant eating fish originally located in the large rivers & streams of eastern China & Siberia. grass carp are one of the largest members of the minnow family and fish as big as 110 pounds have been fished from the Yangtze River in China. A more native size for USA waters would around 20 lbs. Life span for grass carp often is 5 to 11 years, but fish over 20 years of age have been caught in China & Siberia.
grass carp first were brought to the U.S. in 1963 for aquatic plant control studies. Many scientists saw the grass carp as being a natural aquatic weed control method. But, fears of reproducing populations and reports of environmental damage prompted most states to out-law their use.
Triploid grass carp & Diploid grass carp
In 1981, researchers discovered a way to make sterile, non-reproducing grass carp by exposing the fertilized eggs to heat shock. The method results in fish male and female having three groups of chromosomes (triploid) instead of the normal two groups of chromosomes (diploid). Therfore, sterile fish made by this process are referred to as “triploid grass carp.” The United Sates Fish & Wildlife Service has established a testing and inspection protocol to ensure the integrity of triploid grass carp that are destined for importation into states that don’t allow the introduction of diploid grasscarp. Diploid and triploid grass carp can not be ID’d by their external appearance. Determination of the fertility or sterility of grass carp occurs by looking at a drop of blood taken from the fish. United Sates Fish & Wildlife Service inspectors conduct routine testing at the fish farmers’ production sites and provide written certification of triploid condition to the transporter and appropriate officials in each state.
Biology
Triploid grass carp resemble a large creek chub in appearance. These fish do not exhibit the spiny dorsal and anal fin rays or “chin” barbels that are found on most carp. Triploid grass carp are equipped with specially developed pharyngeal bones that perform like teeth and let them rip loose and grind aquatic plants. Triploid grass carp can adapt to a wide variety of water conditions, but, they like it in warm water. Generally, triploid grass carp will start to consume aquatic plants whenever water get over 52°F. Peak aquatic weed consumption and triploid grass carp growth will happen during late spring through summer at water temperatures between from 68°F. to 90°F. Latitude, water temperature, food availability, and age determine peak growth. Triploid grass carp are usually at controlling aquatic weeds for seven to eight years and can tip the scales at 25 pounds or more.
