Florida Triploid Grass Carp

Most people are surprised to learn that the grass carp is actually a very big minnow! It is a member of the largest group of fishes, Family Cyprinidae, which also includes such well-known examples as the goldfish and the golden shiner. It is an exotic species, not native to Florida but moved here by man from its original range in China and Siberia. The grass carp legally stocked by FWC permit are triploid grass carp. They have been genetically manipulated under closely-controlled hatchery conditions to have three sets of chromosomes instead of the normal two. This renders these fish incapable of reproducing—an important precaution in case stocked fish accidentally gain access to an area they were never intended for. For this same reason, the triploid grass carp is not considered an established exotic species (having a permanent population), even though it is quite common in many water bodies. Without restocking, every population will eventually die out. This is the only other legally-stocked exotic fish in Florida besides the peacock bass.

The fish can achieve 56 inches in length and 75 pounds in weight, although much smaller fish are most effective for vegetation control. Grass carp will often school together. The dorsal fin of feeding individuals can sometimes be observed sticking out of the water.

NOTE: Grass carp are illegal to possess without a FWC permit. Any grass carp caught by anglers must be released unharmed.

What grass carp will eat
Grass carp are strictly vegetarian. Their popularity for vegetation control stems from their taste for certain plants often considered troublesome from a lake management perspective. Below are some of the most preferred aquatic plants that grass carp will consume:

  • Hydrilla
  • Southern Naiad
  • Pondweed
  • Chara (Musk-Grass)

What grass carp might eat
There are some plants that triploid grass carp have only a moderate preference for. For these species, grass carp can still provide effective control if none of the more preferred species are present. Usually, some chemical control is still needed, and triploid grass carp may need to be stocked in higher numbers to have a noticeable effect.

  • Coontail
  • Eel Grass
  • Hydrophila
  • Fanwort

What grass carp won’t eat
If one of the plants listed below is what ails your lake, then herbicide control is probably your only option. Triploid grass carp rarely eat these species.

  • Water Hyacinth
  • Water Lettuce
  • Filamentous Algae
  • Cattail

How it’s done
Triploid grass carp will also control some other species of plants, but those above are among the most common. The first step in the process is to determine what species of plant (or plants) are involved. It is very important that you correctly identify the plants that you want to control before stocking triploid grass carp. Otherwise, you will probably be wasting time and money.

Once you have determined that the plants involved can be controlled by grass carp, you will need to apply for a Triploid Grass Carp Permit. In order to obtain the permit, culverts leading out of the water body in question may need to be grated to prevent grass carp from escaping beyond the permitted area. Once approved, the permit will allow stocking of an appropriate number of fish for the situation. The triploid grass carp will have to be purchased from an FWC authorized supplier.

In most situations, the plants being controlled should be treated with herbicide to reduce them as much as possible prior to stocking the grass carp. Once introduced, the grass carp should provide “maintenance control” of the remaining vegetation. Note that grass carp are small when stocked and may not have a discernible effect for up to a year. Therefore, plan for any necessary control until then. Once the fish grow large enough to be effective, regular monitoring and occasional herbicide treatment for control—or stocking of additional fish—may be needed to maintain control of the vegetation within the system.

By hiring a licensed, insured and reputable fish stocking company, you can ensure your residents and neighbors a balanced, healthy fish population.

For more information about South Florida fish stocking contact info@fishstocking.com or call 954.382.9766 and ask for Andy Fuhrman.

Links to Florida Fish Stocking resources:

Allstate Resource Management
Florida Fish and Wildlife Conservation Commission
University of Florida IFAS Extension

Credit: John Cimbaro/Florida Fish and Wildlife Conservation Commission