Aquatic Weed Control: Using Grass Carp
Carp, or white amur, have been used for aquatic vegetation control in Mississippi for the past two decades. These fish, used as a "biological control" for aquatic vegetation, can be effective and cost efficient when stocked at appropriate rates and when the problem-weed species is a plant preferred by carp. Although these fish are voracious herbivores, they exhibit preferences for the softer, low-fiber, high-moisture plants when given a choice. Even when there is no alternative, grass carp will not always provide adequate control of certain plants that they do not prefer to eat.
It is important to identify the problem plant(s) properly and to choose to stock grass carp only when the problem plants are those that grass carp are proven to control. A number of studies have determined grass carp preferences of the various common aquatic plants, and results from some of that work are summarized in this publication. In some cases, although grass carp are listed in the scientific literature as preferring a certain weed, field experience in Mississippi shows them to be ineffective on a consistent basis. Those plants that grass carp do not consistently control are rated as "low" in effectiveness (Table 1).
Table 1. Common Mississippi aquatic plants, preference by grass carp, and effectiveness in providing control in lakes and small impoundments
Common name Scientific
name Preference Effectiveness Coontail Ceratophyllum
sp. High High Bushy pondweed,
Naiad Najas
sp. High High Arrowheads Sagittaria
sp. Moderate Low Willows Salix
sp. Low Low Spikerush Eleocharis
sp. Low Low Hairgrass,
Slender spikerush Eleocharis
acicularis Moderate High Cattail Typha
sp. Low Low Pondweed Potamogeton
sp. Moderate Moderate Bladderwort Utricularia
sp. High High Fanwort Cambomba
caroliniana High High Parrotfeather Myriophyllum
aquaticum Moderate Moderate Water primrose Jussiea
sp. Low Low Smartweed Polygonum
sp. Low Low Filamentous
algae Spirogyra
sp., many others Moderate Low Muskgrass (algae) Chara
sp. High High Stonewort (algae) Nitella
sp. High High Planktonic
algae Many species Low Low Alligatorweed Alternanthera
philoxeroides Low Low Hydrilla Hydrilla
verticellata High High Water hyacinth Eichornia
crassipes Low Low Duckweed Lemna
sp., Spirodella sp. High Low White waterlily Nymphaea
odorata Low Low American lotus Nelumbo
lutea Low Low Burreed Sparganium
sp. Low Low Bulrush Scirpus
sp. Low Low Elodea Egeria densa High High Water fern Azolla caroliniana Moderate Low Water cress Nasturtium
officianale Moderate High Spatterdock,
Yellow cow lily Nuphar
sp. Low Low Sedges Cyperus
sp. Low Low Eurasian water
milfoil Myriophyllum
spicatum Moderate Moderate Frogs-bit Limnobium
spongii Low Low Water hyssop Bacopa Moderate Low Eelgrass Vallisneria
americana Low Low Watermeal Wolffia
sp. High Low
For additional information on the biology and management of grass carp in Mississippi farm ponds, request MSU-ES Publication 1894, Grass Carp in Mississippi Farm Ponds.
By Dr. Martin W. Brunson, Extension Leader/Fisheries Specialist
Information Sheet
1556
Extension Service of Mississippi State University, cooperating with U.S.
Department of Agriculture.
Published in furtherance of Acts of Congress, May 8 and June 30, 1914.
Ronald
A. Brown, Director
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State University. All rights reserved.
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