Grass Carp Facts
The grass carp is a large and non-native species of minnow, brought from eastern sections of Asia during the 1960s to help control aquatic weeds and to provide a potential food fish. The grass carp feeds on the vegetation it finds in the water, consuming large quantities. Grass carp are invasive species in many states, having escaped from ponds into rivers and streams, adversely affecting ecosystems with their diets.
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Identification
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The grass carp, according to the “National Audubon Society Field Guide to Fishes,” may grow to sizes in the range of 39 inches long and weights of 100 lbs. in the very largest individuals. The grass carp has an olive shade, large scales and fins that will be grayish-brown or clear. The grass carp lacks the sensitive barbels—extensions of skin near the mouth that some fish use as feelers—that the common carp possesses. Grass carp have their teeth in their throat instead of their jaws.
Effects
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The effects of escaped populations of grass carp have the potential to be serious on an ecosystem. One is that the grass carp can chew through and devour valuable plant life that creatures such as fish and waterfowl depend upon for food and cover from predators. Another effect grass carp may have is that they can cause the level of phosphorus in waters to elevate with their feeding habits, according to the Minnesota Department of Natural Resources website.
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Benefits
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Grass carp can benefit a pond when used with caution by removing noxious waterweeds such as bladderwort and hydrilla that can deplete the oxygen in a small pond setting. For this reason, authorities introduced the grass carp into ponds in Alabama and then in Arkansas in 1963. Ponds are usually shallow, leading to these weeds taking over if not controlled. The introduction of the grass carp to such scenarios, says the Alabama Cooperative Extension System site, can help remove such weeds. Grass carp can eat as much as three times their body weight in a single day, keeping weeds in check. Unlike their relative, the common carp, the grass carp does not precipitate muddiness in the water with their method of eating.
Legality
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In many states, the introduction of grass carp into a pond requires a permit. In Pennsylvania, for example, it is unlawful to place a grass carp into state waters and it is illegal to have one without such a permit. The Pennsylvania Fish and Boat Commission website notes that a sterile type of grass carp, called a triploid grass carp, is legal with the correct permit. These fish undergo testing to ensure that they will not reproduce and, in turn, harm waterways with their large numbers.
Considerations
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Grass carp females are so fertile that they can lay as many as a million eggs. The grass carp can live in lakes and ponds, as well as large rivers and streams. To reproduce, the grass carp needs to be in flowing water, as the eggs will only hatch if they can stay suspended in moving current for many days. Anglers find it very hard to catch grass carp with rods and reels, as their vegetarian diet makes them finicky, which means it is difficult to attract them to bite at conventional baits.
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