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Carp are members of the minnow family and can grow to very large sizes under the right conditions. There are currently five species of Asian carp in North America that are of concern and they include: common carp (Cyprinus carpio), grass carp (Ctenopharyngodon idella), bighead carp (Hypophthalmichthys nobilis), silver carp (Hypophthalmichthys molitrix), and black carp (Mylopharyngodon piceus). Common carp have been in North America since the late 1800s and are now so widely distributed that they are thought of as a native species in most areas. Asian carp are considered injurious in many areas and in May 2004, the Ontario government placed a ban on buying and selling live bighead, black, silver and grass carp, this was taken further in 2005, with a provincial ban on the possession of live Asian Carp. The ban does not extend to Common Carp which are a popular sportfish for recreational anglers. Similar bans have also been implemented in the United States in many individual states.
Common carp (Cyprinus carpio) is a relatively stout, deep-bodied, high back fish that generally grows to 25-55 cm (12-25 in) and 4-6 kg (8-10 lbs) but can grow much bigger with a North American record of more than 26 kg (57 lbs). The colour ranges from olive-green on the top, to brassy-yellow along the sides and bottom. Distinctive features include a short head; rounded snout; single, long dorsal fin; forked tail; and relatively large scales outlined in black. The mouth is toothless and sucker-like, adapted to bottom feeding, and has two fleshy barbels on either side. Common carp mature at ages 2-4 and spawn in late May to early June in shallow backwaters and along the shoreline. Eggs are deposited on the bottom and stick to objects, such as plants, in the water. Females can lay anywhere from 100,000 to 2 million eggs that hatch within 3-10 days. Carp grow quickly and can live, on average, of 15 years but may live up to 50 years.
Common carp have predominantly vegetarian diets but will also feed on aquatic invertebrates. Their feeding activity has severe impacts on wetland habitats because they suck up sediments and organisms from the bottom, uproot and destroy vegetation and muddy the water.
Grass carp (Ctenopharyngodon idella) is a long, flat-sided fish and is the largest member of the minnow family that generally reaches lengths of 50-90 cm (20-35 in) but can grow well over 1 m (50 in) and weigh over 50 kg (100 lbs). Their colour is similar to common and black carp but lighter overall with an olive back and golden sides. Also similar to common and black carp are the short head, rounded snout, forked tail, a mouth specially adapted to eating aquatic vegetation and large scales outlined in black. It does not posses the fleshy barbels of the common carp, has a much shorter dorsal fin and is more slender. Grass carp prefer to spawn in fast-moving water to keep the eggs buoyant. The fry feed on small organisms until they reach approximately 3 inches in length then they feed exclusively on plant material eating up to their own body weight each day. They live anywhere from 6-11 years.
Sterile grass carp have been used to control aquatic plants in specific areas of the United States and Alberta without fear of reproducing and getting out of control. This method of intentional release in a waterway can be a potentially dangerous practice and is now illegal in Ontario unless authorized by the appropriate authority. There have been numerous instances where grass carp that have been intentionally released have produced established populations.
Bighead carp are a deep-bodied, aptly named fish as it has a large head with eyes that sit lower down on its head and a large up-turned mouth without the barbels of common carp. They can grow to more than 27 kg (60 lbs) in weight and over 1 m (35 in) in length. It has very small scales with dusky green blotches on the back, mottled grey-silvery sides and a white or cream coloured belly. Bighead carp filter feed on tiny animals (zooplankton) and large algae which are strained through their gill rakers that have a fine, comb-like appearance. Bighead carp feed almost continuously and under favourable conditions they grow very quickly.
Bighead carp have been used in the aquaculture industry to filter the waters of lakes and ponds where other fish species, such as catfish, are raised thereby increasing the productivity of the operation. They are also sold and used for human consumption. However, they have escaped from aquaculture facilities and have established populations. Like the grass carp, they spawn in rivers or streams to keep their eggs floating, therefore, will not reproduce in still waters. Females can lay up to a million eggs in one season.
Silver carp are deep-bodied, laterally compressed (narrow) fish with eyes that are low set very similar to the bighead carp except they have a smaller head and mouth, and have very small scales that are uniformly silver in colour with olive on the head and back. They can grow to over 1 m (50 in) in length and weigh over 50 kg (100 lbs). They are very efficient at straining suspended material from the water through use of gill rakers that appear spongy. Adult silver carp mainly consume phytoplankton and detritus and under ideal conditions, they will grow very quickly.
Silver carp have been used in aquaculture and water management to improve water quality because they are very efficient at filtering water. As with most of the carp species of concern, silver carp have escaped or have been released into waterways where they produce established populations. Like the bighead carp, the silver needs some current to spawn so that the eggs will float and develop properly.
Black carp are a longer more cylindrical fish that typically grow to a length of more than 1 m (36 in) and weigh, on average, about 15 kg (33 lbs). They are blackish-brown in colour and have blackish grey fins, a forked tail and large scales outlined in black. Black carp look similar to grass carp in appearance except that the gill rakers are fused and hardened which are used to crush the shells of the clams, snails, crustaceans and mollusks they feed on. A mature black carp can consume an average of 3 to 4 pounds of mussels per day. Currently they are used in research facilities and by some fish farmers to control yellow grub populations and the trematode parasite in cultured catfish. Black carp can live up to 15 years. Females spawn annually, depositing 129,000 to 1.18 million eggs a year, depending on body size.
Black carp were brought to North America by accident in a shipment with grass carp. Black carp escaped into the Osage River in Missouri in 1994 but there is no evidence of an established population there or other waterways. Risks of escapes from flooding and other natural disasters are high, however, and most new operations are government controlled with the hope that they can reduce the risk.
Common Carp (Cyprinus carpio) is one of the most widely distributed fish species in North America ranging from coast to coast from central Canada to central Mexico. They are incredibly hardy and flexible in their habitat choice and environmental tolerances. As a result, common carp are not only widely distributed over a huge area, but generally very successful in areas where conditions are good.
Since the 1960s when grass carp were imported to the United States, they are now widespread in 45 states through accidental and intentional release. In Canada, grass carp was introduced to Alberta in 1987 for research on the control of aquatic vegetation in irrigation canals. Since that time they have escaped to the wild. In Ontario, a grass carp was captured in 1985 in Lake Erie. Three more were captured in commercial fishing nets on separate occasions during 1989 and 1998 in southern Lake Huron. In the fall of 2003, a single grass carp was caught at the mouth of the Don River, Lake Ontario. It is believed that each capture was an isolated occurrence, likely an intentional release that was purchased from the live food fish industry. There is no know established population of grass carp in the Great Lakes at this time.
Bighead carp were accidently introduced to the Mississippi River when floods washed out hatchery and research ponds. They are now distributed throughout the Mississippi, Ohio and Missouri Rivers and their tributaries in at least 19 states. An electrical barrier has been erected on the Chicago Ship and Sanitary Canal to prevent their spread to the Great Lakes. In the year 2000 a large bighead carp was found in Lake Erie. It is believed that the catches in Lake Erie have been isolated incidents of intentional release from the live food fish industry.
Like the bighead carp, the silver carp escaped from hatchery and aquaculture ponds and are now found in much of the Mississippi River drainage basin. Silver carp invaded the Missouri River in large numbers in 2000, and have become a very abundant fish in the river. An electrical barrier is now in place on the Chicago Ship and Sanitary Canal to prevent the spread of this species to the Great Lakes.
Currently black carp are only found in aquaculture and research facilities in the states of Arkansas, Louisiana, Mississippi, Missouri, North Carolina, Oklahoma and Texas. Risks from natural disasters such as floods, hurricanes and tornados in these states make the risk of escape for black carp high. A natural disaster in the Southeast could result in a release of black carp from aquaculture farms (the first and only known introduction of black carp into a natural waterway occurred during a flood; in that instance, the fish were believed sterile and did not establish a population).
Carp have all the characteristics that make them a successful invader. They tolerate a wide variety of environmental conditions and habitats, they eat a wide range of food and they have a very high reproductive rate. Carp grow to a very large size very quickly and become aggressive contenders for resources.
Common and grass carp can do severe damage to wetlands and other aquatic habitats by destroying large quantities of plant life, which is detrimental to some native fish populations and other animals that depend on aquatic vegetation for food, cover and spawning and nursery habitat. Since both types of carp can only digest about half of the plant material it eats, the rest is expelled into the water. This process can enrich the nutrient levels of water leading to algal blooms, reduce water clarity and decrease oxygen levels. Grass carp may also carry several parasites and diseases known to be transmissible or potentially transmissible to native fishes.
Bighead and silver carp are both filter feeders that feed on zooplankton and phytoplankton. They have a voracious appetite and are in direct competition with native fish at the larval and juvenile phases, and in direct competition with certain native fish such as paddlefish, bigmouth and buffalo. Bighead and silver carp are also easily startled by the sound of boat motors and have been known to jump anywhere from 2-3 m (6-10 feet) out of the water as a result. This has lead to serious injuries to boaters and anglers and in some areas where bighead and silver are abundant, it is too dangerous to waterski behind a boat. In some areas where bighead are abundant, they weigh down commercial fishering nets so much that they cannot be pulled up and must be cut. They can be so abundant that in some areas on the upper Mississippi River, bighead, silver, common and grass carp species make up almost the entire number of fish (97%) that are found in fish kills.
Since black carp are still confined to aquaculture and research facilities, one can only speculate on the impacts if they did escape. They would likely compete for food with native species of birds, fish and small vertebrates. They could also cause a dramatic decline in the population of freshwater mollusks, which play an important role in maintaining the health of aquatic ecosystems. Currently, 102 clams, mussels and snails are listed as endangered or threatened, making black carp a serious threat. Black carp also have the potential to negatively affect the cultured pearl industry through predation on commercial mussel species. Additionally, black carp host many parasites and flukes as well as bacterial and viral diseases that could infect sport, food or threatened and endangered fish species.
The ban in Ontario for the live buying and selling of bighead, silver, grass and black carp will go a long way to preventing their accidental or intentional release. As with most invasive species, once carp are introduced, they are almost impossible to control. Currently grass, bighead and silver carp have all escaped from their intended use and are being kept out of the Great Lakes by an electronic barrier that connect the Mississippi River to Lake Michigan. Juvenile carp are often confused with bait species and as a result an unintentional bait release into new habitats contribute to their spread from areas where they are established. Early detection of isolated populations may help slow or restrict the spread of these Asian carp. You can do the following to prevent the spread of grass, bighead and silver carp:
Learn to identify grass, bighead and silver carp
Dispose of bait properly: Do not release bait into the water
Always drain water from your boat, livewell, and bilge before leaving any water access
Never dip your bait bucket into a lake or river if it contains water from another water source
Never dump live fish from one body of water into another body of water
Report new sightings of grass, bighead and silver carp by calling the Invading Species Hotline at 1-800-563-7711.