Triploid Grass Carp Permit
Grass carp are fish imported from Asia for use in controlling aquatic vegetation. One of the few fish species which eat plants, grass carp may provide a low-cost, long-term, herbicide-free means of dealing with problem plants in your pond or lake. The designation of triploid signifies that they have been genetically altered at hatcheries to prevent the fish from spawning in Florida waters. A United States Fish and Wildlife Service inspection program helps certify the ploidy of the fish based on a procedure developed by Florida fisheries biologists (Wattendorf, Robert J., 1986. Rapid Identification of Triploid Grass Carp with a Coulter Counter and Channelyzer. Progressive Fish-Culturist. 48(2):125-132)
Do you really have a plant problem?
Plants are a natural part of Florida lakes. Aquatic vegetation provides areas used for feeding, reproduction and shelter for numerous species of fish, amphibians, reptiles and birds.
Often, plant problems in ponds and lakes are due to invasive, exotic species such as hydrilla, which have no natural enemies in Florida. It is in everyone's interest to prevent these plants from spreading.
Fisheries biologists recommend up 30 to 50 percent plant coverage as a healthy balance. If your pond or lake has fewer plants than this, you may not even have a problem.
Are triploid grass carp the answer?
To best determine whether triploid grass carp can solve your plant problem you must answer the following questions:
What type of plant is causing this problem?
Triploid grass carp have definite preferences for certain types of plants. Others they will not eat at all.
To identify your problem plants contact the Invasive Plant Management field office nearest you. A black and white handout that you can easily print to help you identify common Florida aquatic plants is also available.
What are my other plant-control options?
There are two other plant control options which can be used either separately or in conjunction with grass carp. Mechanical control uses machinery to harvest and remove the problem vegetation from the water. Chemical control (herbicides) can be more specific to a particular type of plant and, like mechanical control, can target specific areas within the water body.
Note: Using mechanical or chemical control may require a permit from the Invasive Plant Management Section.
What do I need to know about triploid grass carp?
Cost: Triploid grass carp cost between $5 and $15 each and are usually stocked at three to ten fish per acre, resulting in costs as low as $15 per acre. In comparison, herbicides cost between $100 and $500 per acre and mechanical control may cost more than twice that.
Time: Grass carp usually take six months to a year to be effective in reducing problem vegetation, although they provide much longer term control than other methods, often up to five years before restocking is necessary. When used in conjunction with an initial herbicide treatment, control of problem vegetation can be achieved quickly, and fewer carp are required to maintain the desired level of vegetation.
Overstocking: Once stocked in a lake or pond, carp are very difficult to remove. If overstocking occurs, it may be ten years or more before the vegetation community recovers. Even after carp are removed, other herbivores such as turtles may prevent the regrowth of vegetation.
Water Clarity: Aquatic plants remove nutrients in the water. When plants are removed, nutrients may then be utilized by phytoplankton, turning the water green. Clarity may be improved by reducing or eliminating sources of nutrients into the lake such as road runoff and lawn fertilizer.
Inflows/Outflows: It is in the best interest of people stocking carp to keep them in the desired lake or pond. It is also a required condition of the permit. Any inflows or outflows through which carp could escape into other waters require barriers to prevent fish from escaping into waters not permitted.