Asian Carp

Four species of large Asian carps (grass, bighead,silver and black) have been imported into the U.S. foruse in the aquaculture industry, and biologists areraising more and more concerns about their effect onnative fish and shellfish when released or escaped tothe wild. In fact, in the fall of 1999, fish kills in isolatedditches adjacent to the Upper Mississippi River on theMark Twain National Wildlife Refuge in southernIllinois included large numbers (97%) of Asian carps,but only one individual each of four native fish species.After that incident, reports came in of commercialfishermen having to abandon fishing sites on theMissouri River because they were catching so manyAsian carps that they found it impossible to raise theirnets. The common carp, introduced by Europeanimmigrants in the 1800’s as a food fish, has become sowidespread in the U.S. that in most areas it is consid-ered part of the native fauna. The fear is that in timethe other four Asian carps will become as widelydistributed and abundant, wreaking widespread havocwith native fish and shellfish habitats and foods.

Grass carp (Ctenopharyngodon idella): The grasscarp or white amur, native to eastern Asia, was first

sippi River Basin, with huge numbers and significantnatural reproduction being documented by biologistsin off-channel and backwater habitats.

Black carp (Mylopharyngodon piceus): The blackcarp is native to most Pacific drainages of eastern Asia.It was first brought to the U.S. in the early 1970’s as a“contaminant” in imported grass carp stocks deliveredto a fish farm in Arkansas. The species closelyresembles the grass carp in appearance, except that thegill rakers are fused and hardened (looking almost likehuman molars) for use in crushing the shells ofmollusks and crustaceans, the black carp’s primaryfood. A second importation occurred in the early1980’s; this time for use as a food fish and as abiological control agent to combat the spread of atrematode parasite in cultured catfish. The first recordof escapement or release to the wild occurred inMissouri in 1994 when thirty or more black carpescaped into the Osage River in Missouri when highwater flooded holding ponds at a private aquaculturefacility near Lake of the Ozarks. Black carp are cur-rently being used by fish farmers for control of snails,the intermediatehost of a trematodeparasite in catfish.Many MississippiRiver Basin stateshave requestedthrough theMississippiInterstate Coopera-tive ResourceAssociation(MICRA), that theU.S. Fish andWildlife Serviceregulate the use ofblack carp by placing it on the federal list of injuriouswildlife species under the Lacey Act. Most states feelthat black carp pose a serious threat to native molluskand snail species, many of which are federally listed asthreatened or endangered. Meanwhile, Mississippi,Arkansas, Texas and Missouri permit stocking ofgenetically altered and presumably sterile black carp infish farm ponds. Missouri has also initiated a 5-yearprogram to supply limited numbers of genetically

altered black carp to fish farmers in the hope that stateofficials will be more successful than private operatorsin preventing the escape and spread of this non-nativespecies. Unfortunately, however, black carp have beenconfirmed in the wild at Horseshoe Lake (2003) near theUpper Mississippi/Ohio river confluence and in theRed River in Louisiana (2004) near the Lower Missis-sippi/Atchafalaya river confluence.

What Can You Do? Become more informed about thespread of non-native species nationwide. Consult yourlocal, state, and federal conservation authorities as tothe threat of non-native species in your area, and to thelaws and regulations governing the importation,culture, maintenance, and stocking of non-nativespecies. Utilize care in the purchase and use of baitfishin lakes and streams. Ask your bait dealers where theirbaitfish came from, and never release any unusedbaitfish to the wild; always destroy them or return themto your bait dealer. Learn and understand the biologyand needs of aquarium fish species before purchasingthem for your home aquarium. Never release pet fish oraquatic organisms from the home aquarium to openwaters. Either destroy them, sell or give them tosomeone else, or return them to the store wherepurchased for proper disposal. Support stronger local,state and federal regulations designed to prevent thespread of non-native species, and let others know ofyour concerns for the protection of native species andbiodiversity. Support your local, state and federalnatural resource agencies in all of their efforts to stopthe spread of non-native species of any kind!

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Revised - 30 April 2004

Bighead carp (50 lbs) caught in the Cumberland River,Tennessee in May 2000.

imported into the U.S. in 1963 to aquaculture facilities inAuburn, Alabama and Stuttgart, Arkansas for researchin the control of aquatic vegetation. This speciestypically inhabits large rivers but can be raised inponds and rice fields; and large individuals are knownto consume many pounds of aquatic vegetation in asingle day. The first release into open waters occurredas a result of escapement from the Fish FarmingExperiment Station in Stuttgart. By the mid-1960’s theArkansas Game and Fish Commission was raising thespecies at a state fish hatchery in Roanoke; and by1978 Arkansas biologists had stocked the species inmore than 100 state lakes. Since that time grass carphave rapidly spread to45 states through theaccidental andintentional, legal andillegal release bynumerous state andfederal agencies,private groups andindividuals. Despiteefforts to control thespread of grass carpby stocking individu-als thought to besterile, this large (50+lbs), elongate, stout-bodied, blunt-headed, pale gray minnow has estab-lished itself and is reproducing in the wild. Grass carpbegan to appear in the catches of Arkansas’ commercialfishermen in the early 1970’s, and by 1976, 25 tons werereported taken statewide. The species has limitedpotential as a gamefish, and as a food fish the flesh isoften said to be tainted with a strong algal flavor.However, local demand for and acceptance of grasscarp is reported to be very high in some markets. Grasscarp are regarded as the most palatable of all of theAsian carps. While introduced to consume trouble-some aquatic plants, grass carp have been known toclean entire lakes of all aquatic plants, and to thenconsume organic detritus and animal materials. Nega-tive impacts on native organisms have been summa-rized to include: interspecific competition for food withinvertebrates (i.e., crayfish) and other fishes; signifi-cant changes in the composition of macrophyte,

phytoplankton, and invertebrate communities; interfer-ence with the reproduction of other fishes; decreases inrefugia for other fishes; modification of preferred fishhabitats; enrichment and eutrophication of lakes;disruption of food webs and trophic structure; andintroduction of nonnative parasites and diseases.

Bighead carp (Hypophthalmichthys nobilis): Bigheadcarp, native to the large rivers of eastern China such asthe Yangtze, were first brought to the U.S. in 1972 by aprivate fish farmer in Arkansas who wanted to use themto improve water quality and increase fish productionin culture ponds. By 1974 the species was beingevaluated by the Arkansas Game and Fish Commissionand Auburn University for its potential biologicalbenefits and impacts. Bighead carp first began toappear in open public waters (i.e. the Ohio and Missis-sippi rivers) in the early 1980’s, likely the result ofescapement from fish farms and aquaculture facilities.The species has now been recorded from within, oralong the borders of, at least 18 states, and is reportedto be “piling up” in large numbers below dams on manyMidwestern rivers,and filling the nets ofcommercial fishermento the point that netscan’t be lifted andfishing sites have tobe abandoned. Thebighead carp is avery large deep-bodied, somewhatlaterally compressed(narrow) fish with avery large head.Scales are very tiny,resembling those oftrout, and the eyesare situated belowthe midline of thebody. Gill rakers arelong, comblike and close-set allowing the species tostrain plankton organisms from the water for food. Thebighead carp utilizes open water areas, moving about inthe euphotic (surface) zones of large lowland rivers,consuming large quantities of bluegreen algae, zoop-

lankton, and aquatic insect larvae and adults.Because of it’s feeding habits, the species is a directcompetitor with the native paddlefish, bigmouthbuffalo, and gizzard shad; as well as with all larvaland juvenile fishes and native mussels. Somecultures value the flesh of bighead carp as a sourceof food protein and prefer that these fish be keptalive until immediately before cooking. Suchdemands are growing, particularly in cities with largeethnic Asian communities.

Silver carp (Hypophthalmichthys molitrix): Thesilver carp, native to eastern Asia and the Amur andother lowland rivers of China, was also first broughtto the U.S. by an Arkansas fish farmer in 1973,apparently for use in phytoplankton control inponds and as a food fish. By the mid 1970’s, it wasbeing raised at six state, federal, and private facilitiesin Arkansas; and by the late 1970’s it had beenstocked in 4 municipal sewage lagoons. This deep-bodied, laterally compressed (narrow), very largeminnow is similar to the bighead carp, but muchmore efficient at straining suspended material fromthe water through use of gill rakers that are fusedinto sponge-likeporous plates. By1981, the silver carpappeared in Arkan-sas’ natural watersat 7 different sites,likely the result ofescapement fromaquaculturefacilities. The silvercarp’s history anduse in Arkansas areclosely intertwinedwith that of thebighead carp; anddue to its feedinghabits, the silvercarp is also a direct competitor with all native fishlarvae and juveniles; with adult paddlefish,bigmouth buffalo and gizzard shad; and with nativemussels. The silver carp is presently spreadingrapidly throughout the large rivers of the Missis-