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Grass Carp

grass carp pictures The Grass Carp (Ctenopharyngodon idella) is a herbivorous, freshwater fish species of family Cyprinidae, and the only species of the genus Ctenopharyngodon. It is cultivated in China for food but was introduced in Europe and the United States for aquatic weed control.

It is a large cyprind native to Eastern Asia, with a native range from Northern Vietnam to the Amur River on the Siberia-China border. It is a fish of large, turbid rivers and associated floodplain lakes, with a wide degree of temperature tolerance.

Grass carp are usually thought to enter reproductive condition and spawn at temperatures of 68°F to 86°F (20°C to 30°C), but have been shown to sometimes spawn at temperatures as low as 59°F (15°C).

Description Of White Amur

grass carp pictures

In the United States, the Grass Carp is also known as White Amur, a name developed to avoid use of the name "carp", which has derogatory connotations in North America. The name derives from the Amur River, where the species is probably native, but has never been abundant.

The grass carp is one of the largest members of the minnow family. The body is oblong with moderately large scales, while the head has no scales. There are three simple and seven branched rays on the dorsal fin.

Grass carp or White Amur are silvery to olive in color, lacking the golden hue of common carp, and they have no barbels.

This species typically reaches sizes of 65 to 80 pounds in its native habitat, but individuals approaching 400 pounds have been reported.

Facts About The Grass Carp

Are only distantly related to the undesirable European carp, and share few of its habits.
Live for at least ten years.
Will grow rapidly and reach at least ten pounds. They have been known to reach 40 pounds in the southern United States.
Will not eat fish eggs, young fish or invertebrates, although baby grass carp are omnivorous.
Feed from the top of the plant down so that mud is not stirred up. However, in ponds and lakes where grass carp have eliminated all submerged vegetation the water becomes turbid. Hungry fish will eat the organic material out of the sediments.
Have definite taste preferences. Plants like Eurasian milfoil and coontail are not preferred. American waterweed and thin leaved pondweeds are preferred.
Are dormant during the winter. Intensive feeding starts when water temperatures reach 68°F.
Are a river fish and have the desire to move from still waters into flowing waters.
Are difficult to recapture if a waterbody has been overstocked.
They may not feed in swimming areas, docks, boating areas, or other sites where there is heavy human activity.

Advantages Of The Grass Carp

Grass carp are inexpensive compared to some other algae control methods and offer long-term control, but fish need to be restocked at intervals.
Grass carp offer a biological alternative to aquatic plant control.

Disadvantages Of The Grass Carp

Depending on plant densities and types, it may take several years to achieve plant control using grass carp and in many cases control may not occur or all submerged plants may be eliminated.
The type of plants grass carp prefer may also be those most important for habitat and for waterfowl food.
If the waterbody is overstocked, all submersed aquatic plants may be eliminated. Removing excess fish is difficult and expensive.
If not enough fish are stocked, less-favored plants, such as Eurasian milfoil, may take over the lake.
Stocking grass carp may lead to algae blooms.
All inlets and outlets to the lake or pond must be screened to prevent grass carp from escaping into streams, rivers, or other lakes.

Grass Carp For Weed Control

When used for weed control, often the fish introduced to the pond or stream are sterile, triploid fish. The process for producing triploid fish involves shocking eggs with rapid change in temperature or pressure. This process is not usually 100% effective, therefore, in the United States, the young are usually tested for triploidy before being sold. Bait often consists of vegetables or fruits that are native to the area.

The species was deliberately introduced into the United States in 1963 for aquatic weed control. It was introduced into New Zealand along with stocks of goldfish but the distribution is carefully controlled to prevent it from becoming a more widespread pest.

The Grass Carp is considered an invasive species in the United States, however it is still stocked in many states as an effective biocontrol for undesirable aquatic vegetation, many species of which are themselves invasive.

References: Texas State

References Wikipeda Encylopedia

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Grass Carp: A Fish for Biological Management of Hydrilla and Other Aquatic Weeds in Florida

A pretty Interesting read for facts about the Grass Carp you may not have known. Description of Grass Carp: How the Grass Carp eats, what it prefers to eat, water temperatures it prefers and more.

Using Grass Carp in Aquaculture and Private Impoundments

Has a table for states that need a permit for stocking grass carp in U.S. Diploid versus triploid. This file has detailed information on the description of Grass Carp.

Appearance

White amur have an elongate, chubby body form that is torpedo shaped. The terminal mouth is slightly oblique with non-fleshy, firm lips, and no barbels. The complete lateral line contains 40 to 42 scales. Broad, ridged pharyngeal teeth are arranged in a 2, 4-4, 2 formula.

The dorsal fin has 8 to 10 soft rays, and the anal fin is set closer to the tail than most cyprinids. Body color is dark olive, shading to brownish-yellow on the sides with a white belly and large slightly outlined scales.

The grass carp grows very rapidly, and young fish stocked in the spring at 20 centimetres (7.9 in) will reach over 45 centimetres (18 in) by fall, and adults often attain nearly 1.2 metres (3.9 ft) in length and over 18 kilograms (40 lb) in weight. They eat up to 3 times their own body weight daily.

They thrive in small lakes and backwaters that provide an abundant supply of fresh water vegetation.

Ecology

This species occurs in lakes, ponds, pools and backwaters of large rivers, preferring large, slow-flowing or standing water bodies with vegetation. In the wild, grass carp spawn in fast-moving rivers, and their eggs, which are slightly heavier than water, develop while drifting downstream, kept in suspension by turbulence. The eggs are thought to die if they sink to the bottom.

Adults of the species feed primarily on aquatic plants. They feed on higher aquatic plants and submerged terrestrial vegetation, but may also take detritus, insects, and other invertebrates.