Triploid Grass Carp Facts & Figures

Home Weeds Barriers

The Science of Triploidy in layman's terms:

Diploid grass carp, as most fish, are capable of sexual reproduction. Triploid grass carp, however, have three sets of chromosomes and are incapable of normal sexual reproduction. Three sets of chromosomes are produced by physically shocking fertilized eggs with heat, cold, or hydrostatic pressure; thus stimulating the retention of a set of chromosomes that would normally be expelled during cell division.

My opinion on stocking size:

Large grass carp (12" and above) eat more than smaller ones. Small fish (less than 8") suffer high mortality due to predation by birds, snakes, and other kinsmen. Fish weighing less than 6.6 lbs (measuring up to about 24" in length) eat 100 percent of their body weight daily. Since TGC measuring above 12" is almost an impossibility to locate and purchase, this necessitates the stocking of smaller fish in the 8" to 12" range, sometimes in conjunction with the use of alternative controls.

Stocking Calendar:

Plant control strategy, water quality, and availability of fish determine when you should stock. If grass carp are used in conjunction with other control methods, they should be stocked after the treatments have done their jobs but before re-growth begins. Typically, your lake will look its worst around the end of summer, but water temperatures are still too warm to stock. I have found the cooler months of October-May are the easiest on the fish and are the best time for transporting and stocking. Since spring is the big "TGC Sale" time when the problem aquatic plants begin to emerge, availability may require patience on your part.

My Stocking Equation:

To achieve effective control of problem plant species, TGC must be stocked in sufficient numbers so that they eat more plant than the lake produces. Consumption and stocking rates depend on: 

  • Size of available fish (preferred is 10-12")

  • Plant density

  • Size of the water body

  • Water temperature

  • Movement of TGC

  • Whether mechanical or herbicide treatments have been used 

Rate  TGC Size Stock per Acre
 Low   8-10"   3-  6
 Low 10-12"   2-  5
 Medium   8-10"   7-18
 Medium 10-12"   6-15
 High   8-10" 19-36
 High 10-12" 16-30

TGC are like children -- picky eaters who grow fast when their favorites are bountiful:

Triploid grass carp efficiently control and preferentially feed on some types of plants and avoid others as shown in the following table. Avoided plant species are better controlled with alternate methods. Fiber content, which varies among plant parts and plant species, significantly influences the plant's palatability. Low-fiber plants are preferred, and stocking in spring allows TGC to feed on new growth of fibrous plants. Water temperature affects feeding in the following ways:

  • feeding stops when the water temperature reaches 52° F

  • declines at water temperatures above 86° F

  • is optimum at water temperatures from 68-86° F

Will Consume May Consume May Consume to Survive
Hydrilla Azolla or water fern Stonewart
Southern Naiad Hyssop Coontail
Duckweeds Slender spikerush Cattail
Coastal Arrowhead Watercress Spadderdook
Eastern Bladderwort Pondweeds Water lily
Watermeal Algae Watermilfoil
Fanwort   Eel grass
Muskgrass   Parrot feather
Elodea   Water hyacinth
    Water primrose

Where do I go from here:

Lake owners may take plant samples to local offices of the Agricultural Extension Service, the Florida Fish & Wildlife Commission (FFWC), or Department of Environmental Protection for identification. Just put the sample in a zip lock bag. If you prefer, I will come to your lake to have a look, either from the shore or by boat. Once specific weeds are identified, then we will develop a plan like this:

  • Identify your problem plant(s)

  • Determine if you should eliminate or selectively manage aquatic plants

  • If using triploid grass carp, contact the FFWC for a permit application or go to FFWC

  • If there are inlets or outlets on your water body, the FFWC will inspect and may require barriers to be installed. As you will see on my barrier page, this is a good thing.

  • Once the permit is obtained, contact me for pricing and availability and to stock your lake with triploid grass carp.