In later 1980, fisheries scientists from Louisiana State University, while collecting fish population data in the Mississippi River, determined grass carp had been reproducing in areas of this major river system since 1975. As a result of this discovery, along with staff findings on potential impact, the Commission prohibited the use of the diploid grass carp and thus initiated a stocking program utilizing the triploid grass carp, a (sterile), fish produced in Florida and Arkansas.
The Commission has been permitting the use of triploid grass carp for the private sector, on a limited basis, to control submersed aquatic vegetation. This program was established to provide relief to owners of lakefront property on closed or semi-closed systems, troubled with dense strands of undesirable aquatic plants as an alternative to the widespread use of herbicides in Florida.
The triploid grass carp will remove hydrilla, when stocked in adequate numbers, from ponds and small lakes. There is some evidence the fish may also eat the growth of emergent species such as the fragrant water lily and the alligatorweed. The Commission stocks the triploid grass carp for the control of submersed aquatic vegetation at 5 to 40 fish per acre depending on the species of vegetation present in the water area, and the length of the fish. There is no size limit on fish stocked for private waters, however, it should be noted that largemouth bass will feed on small triploids.
If chemical control were to be used the cost would run from $220-$400 per acre. And since two or three chemical treatments may be needed to control the vegetation in a body of water, the cost of purchasing grass carp would prove to be much less expenive, then an ongoing chemical control program.
Types of vegetation that triploid grass carp can help control are, hydrilla and chara, and types of duckweed. Not effectively controled by the triploid carp is vegetation like, eelweed and Eurasian watermilfoil, smartweed and stonewort, water hyacinth and American lotus, yellow water lily and fragrant water lily, maidencane and dollarweed, alligatorweed and torpedograss, and cattails.
The difference between the diploid grass carp and the triploid grass carp, is that the diploid grass carp is capable of reproducing and the triploid grass carp can not reproduce.
