Greene County Soil & Water Conservation District Grass Carp

In recent years, there has been increasing interest in the set of various biological controls for aquatic weeds. For instance, Barley straw has been found to be effective in the treatment of filamentous as well as blue green algae. Another form of biological control, is the use of "grass carp" for the control of submergent weeds. To many, the use of grass carp is no more favorable than chemical weed control due to the devastating impact Grass Carp can have on native plant populations. While all states regulate the use of Grass carp, and require certain protections to try and keep the species out of area where vegetation is desirable for a healthy fisheries population, the fact is they have now spread to many of our waters and their long term impact is still uncertain The Grass Carp is the largest member of the minnow family, and are related to both common carp and goldfish. Grass Carp, also know as the White Amur are native to the rivers of Eastern China and Russia, and the species was introduced to the US in 1963 by the US Fish & Wildlife Service as a potential control for aquatic weeds. Grass carp lack barbels and spiny dorsal and anal fins and more resemble a large creek chub or shiner with coloration from dark grey to golden brown on their backs blending to a white belly. Grass carp feed strictly on aquatic vegetation and are not bottom feeders. Juveniles feed on plankton, but switch to vegetation when they are around 6" in length In the US, landowners can only stock triploid carp as they are sterile and unable to reproduce. Since they are strict herbivores they do not compete for food with other game species nor do they consume fingerlings of other fish species. When temperatures exceed 68 F., the Carp feed almost continuously and may eat several times their body weight in a single day under optimal conditions. They may attain average weights of 20-25 ponds and over 3' in length. The average life span is 10 years but their "appetite declines with age Stocking Rates Since Grass Carp have the potential to eradicate all plant growth in a pond for an extended period (up to 10 years) they must be stocked carefully. Loss of all vegetation can cause severe algae blooms, foul odors and loss of water clarity as well as impact game fish and other aquatic organisms. It is recommended that carp be managed such that plant populations are maintained at a minimum of 20-30% of the waters surface. DEC will specify a rate for an initial stocking, which should be monitored for at least two years before adding additional fish in small increments until such time the desired rate of control is achieved.

Stocking Grass Carp in NYS In NYS, the use of Grass Carp for weed control is strictly regulated by NYSDEC. In order to purchase and stick the fish, both the landowner and the distributor must be licensed.. In NY, DEC policy is to limit stocking rates to no more than 15 fish per surface acre for those ponds of 5 acres or less and size and when contained wholly within the boundaries of land privately owned or leased by the applicant and the following conditions are met; Aquatic plants must significantly impair the intended use of the pond 1. No endangered, threatened or species of special concern shall be present in the proposed stocking area 2. The pond is not contigous to part of a NYS regulated wetland 3. The pond is not a natural or manmade impoundment on a permanent streamas shown on USGS topo maps 4. At least two years have elapsed from the date of the last stocking unless demonstrated that previous stocking had high mortality.

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