Grass Carp

Grass Carp
aka: White Amur
Kasie Hennessey
September 10, 2011
Grass Carp
• Grass Carp are also known as White Amur
(however, they are only called this in the United
States to avoid the derogatory term “carp”)
• They are a herbivorous, freshwater fish
• They are native to Malaysia, the river system of
northern China and southern Siberia
• They were imported by the U. S. Fish and
Wildlife Service in 1963 for research in aquatic
plant control.
Grass Carp
Grass Carp Size
• Grass Carp can reach a size of at least 35 to 40
lb. in ponds in mid-western states.
• Their life expectancy is 8 to 12 years. Some do
live longer, but the larger they get the less they
eat so they are less effective in plant control.
• Older fish give the impression of being related
to submarines. They can reach 4 feet and 100+
pounds in their native rivers.
• Amur are usually stocked at 10 to 12 inches. An
8 inch minimum is a required to keep them from
becoming expensive bass food!
Interesting Facts About Grass Carp
• 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.
• In ponds and lakes where grass carp have eliminated
all submersed vegetation the water becomes smoky.
Hungry fish will eat the organic material out of the
Interesting Facts About Grass Carp
• Are dormant during the winter. Intensive
feeding starts when water temperatures reach
52 degrees.
• Are a river fish and prefer flowing waters to still
• Are difficult to recapture. So, make sure you
REALLY want them in your pond or lake.
• They may not feed in swimming areas, docks,
boating areas, or other sites where there is
heavy human activity.
Cool Facts about Grass Carp
• Grass carp possess specially developed
pharyngeal (tube that connects the mouth
and nasal passages with the esophagus)
bones that perform like teeth and let them
tear free and grind aquatic plants.
• Latitude, water temperature, food
availability, and age determine how large the
grass carp will grow.
WHY have Grass Carp???
• Grass Carp or White Amur can effectively control aquatic
vegetation in ponds and lakes.
• Yearly chemical weed control can costs thousands of
• Grass carp are very cheap, costing on average about $10$20 per fish.
• 10 grass carp per acre would only cost you about $140.00
per acre and the grass carp will control weed growth for 6
to 8 years.
• Grass carp are very effective in controlling submersed
grasses and can eat up to 5 times their body weight in one
• They will live longer than 8 yrs, but the larger fish do not
control vegetation like the younger actively growing ones.
Videos on Grass Carp
Triploid Grass Carp
• Grass carp possess specially developed pharyngeal (tube
that connects the mouth and nasal passages with the esophagus)
bones that perform like teeth and let them tear free and
grind aquatic plants.
• In 1981, researchers developed a method to create
sterile, non-reproducing grass carp by exposing the
fertilized eggs to heat shock. These sterile grass carp
are called triploid.
• Determination of the fertility or sterility of grass carp
occurs by analyzing a drop of blood taken from the fish.
• This process results in fish of both sexes having three
sets of chromosomes (triploid) instead of the normal two
sets of chromosomes (diploid).
• Predatory fish, such as largemouth bass, eat grass
• If used with existing fish populations, grass carp
should be large enough to avoid being eaten by
the average size predator.
• Even if predation is not a problem, the pond
owner should consider using larger carp if they
are available because they tend to survive
handling and stocking better.
• Grass carp stocked with existing fish populations
should be at least 8-10 inches in length.
• Grass carp do not reproduce in ponds and
periodic restocking is required.
• Once stocked, grass carp are difficult to
remove from a pond. They are almost
impossible to remove by seining (fishing with
nets) or angling(fishing with hook and line).
The only options are draining the pond or
using toxins.
Disadvantages of Grass Carp
• Depending on plant densities and types, it may
take several years to achieve plant control using
grass carp.
• The type of plants grass carp prefer may also be
those most important for habitat and for
waterfowl food.
• If the area is overstocked, all submersed aquatic
plants may be eliminated.
• Removing excess fish is difficult and expensive.
Disadvantages of Grass Carp
• If not enough fish are stocked, less-favored
plants, such as Eurasian milfoil, may take over the
• 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.
• In some areas the grass carp are required to be
sterile (tripolds)
• In many cases there is an ALL or NOTHING
approach to weed control.
Longevity and Persistence of Triploid Grass Carp Stocked into the Santee
Cooper Reservoirs of South Carolina. Journal article J. Aquat. Plant Manage. 41:
90-92 by: James P. Kirk and Robin C. Socha
• Http://

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