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.

Invasive species

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;^[11] however, it is still stocked in many states as an effective biocontrol for undesirable aquatic vegetation, many species of which are themselves invasive. Grass carp require long rivers for the survival of the eggs and very young fish.

Use as weed control

The species was introduced in the Netherlands in 1973 for overabundant aquatic weed control. The release into national waters is controlled and regulated by the Dutch Ministry of Agriculture, Nature and Food Quality. Because grass carp mainly reproduce in water of 25 °C (77 °F), which is much higher than the water temperature reaches during the mating season in the Netherlands, it is necessary to maintain grass carp populations by artificial means, which is done by the person responsible for the water body in which the fish were introduced. Where grass carp populations are maintained through stocking as a biocontrol for noxious weeds, they should be returned to the water alive and unharmed.

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 a 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.

Fishing for grass carp

G

A grass carp caught using white bread and six-pound test, monofilament line

rass carp grow large and are strong fighters on a rod and reel, but because of their vegetarian habits and their wariness, they can be difficult to catch.Chumming with corn adds to success. Canned corn, cherry tomatoes, and, despite their primarily vegetarian habits, grass carp sometimes eat other vegetarians. Chumming with white bread, and a piece of bread pinched on a hook and floated on the surface works well, especially for pond grass carp. The fish are popular but wary quarry for bowfishers where bowfishing for grass carp is legal.

When searching for grass carp to fish, one may often spot fish cruising near the surface or very close to the shoreline. Often, an angler will spot a telltale swirl in the water near the shore without even glimpsing the fish. Grass carp often feed or rest near the shoreline, and are very wary in such places. They usually will dart away at the first sight of a person walking nearby. Stalking the fish to place a piece of bait nearby is sometimes successful. Casting bait on top of the fish usually results in spooking the fish.

Grass carp caught in ponds and lakes where they were stocked for weed control should be handled with care and released without harm.