Invasive Asian Carps in North America

<em>Abstract</em>.—The black carp <em>Mylopharyngodon piceus </em>is a large (>1 m long) riverine fish from eastern Asia introduced into the United States via the aquaculture industry. A wild population has been present in the lower Mississippi River basin since the early 1990s, but little is known about the ecological effect of black carp in invaded environments. In its native range, black carp feed almost exclusively on mollusks. In U.S. waters, they likely prey on native mussels, but few wild-caught specimens have been examined by biologists and all have had empty gastrointestinal tracts. In lieu of stomach content data, we examined isotopic values (δ¹³C and δ ¹⁵N) and mercury (Hg) concentrations in muscle tissue of black carp and 10 other large nonnative and native fish species captured in the Red–Atchafalaya River system of Louisiana, USA. Trophic position estimates derived from δ ¹⁵N values ranged from 2.0 for grass carp <em>Ctenopharyngodon idella </em>to 4.8 for blue catfish <em>Ictalurus furcatus </em>and flathead catfish <em>Pylodictis olivaris</em>. Adult black carp had a δ ¹⁵N value (13.2‰), indicating a trophic level of 3.5. Mean total Hg concentrations ranged from 0.02 µg/g in grass carp to 0.27 µg/g in bigmouth buffalo <em>Ictiobus cyprinellus</em>, in black carp 0.17 µg/g; Hg increased with increasing δ ¹⁵N, indicating biomagnification. The limited numbers of taxa and small samples sizes, as well as constraints in methods used, do not allow confirmation that wild black carp are consuming native mollusks. However, our stable isotope results do provide evidence that its diet is similar to other large fish species inhabiting the Red–Atchafalaya system considered to be benthic invertivores, including some known to prey on freshwater mollusks (i.e., smallmouth buffalo <em>I. bubalus </em>and nonnative common carp <em>Cyprinus carpio</em>).

Invasive Asian Carps in North America

<em>Abstract</em>.—There are four species collectively known as the Asian carps: grass carp <em>Ctenopharyngodon idella</em>, bighead carp <em>Hypophthalmichthys nobilis</em>, silver carp <em>H. molitrix</em>, and black carp <em>Mylopharyngodon piceus</em>. These species have been introduced worldwide for aquaculture purposes. Subsequent to introduction into the southern United States, three species have become well-established in the wild (grass, bighead, and silver carps). Two of these species, bighead and silver carps, have been dispersing rapidly up the Mississippi River basin, wreaking ecological havoc along the way. As there are numerous connections between the Mississippi basin and Canadian watersheds, including the Great Lakes, there is considerable concern about their potential ecological impacts if introduced and established in Canada. In addition to natural dispersal, these species may also be introduced into the Canadian wild through the live food fish trade. In 2004, the Canadian federal department of Fisheries and Oceans Canada conducted a risk assessment to determine the ecological risk of Asian carps to Canada. This assessment included evaluating the risk of survival, reproduction and spread of these species, as well as their pathogens, parasites, or fellow travelers (e.g. other invasive species), should they be introduced into Canada. These components were assessed in an expert workshop using best available information on their biology, potential vectors of introduction, and impacts in both native and introduced ranges. The assessment concluded that the risk of impact was high in, at least, some parts of Canada, including the southern Great Lakes basin by all four Asian carp species.

Invasive Asian Carps in North America

<em>Abstract</em>.—The directed extinction of an exotic fish population is proposed using a genetic approach to drastically reduce the ratio of females to males within the population. In the proposed strategy, sex-reversed female fish containing two Y chromosomes (Fyy) are introduced into a normal fish population. The frequencies of each of the four expected genotypes of fish in the simulated population (Fxx, Fyy, Mxy, and Myy) were modeled with a set of coupled ordinary differential equations. The equations take into account birth rate, death rate, and a fixed carrying capacity of the system. Using computer-generated simulations, it was determined that the continuous introduction of a relatively small proportion of Fyy females to the normal population leads to extinction of the exotic fish over time. The proposed eradication strategy is relevant to fish species with an XY sex-determination system that tolerate a YY genotype. Published literature suggests that Asian carps are likely to fulfill these criteria. However, technical barriers associated with sex reversal in Asian carps presently exist and must be overcome before implementation of a YY eradication strategy for Asian carps can be considered in practice. An idealized theoretical model for the eradication of Asian carps is thus presented.

Invasive Asian Carps in North America

<em>Abstract</em>.—Regulations are one of the few tools available in the aquatic invasive species (AIS) management toolbox. In a perfect world, they could be used to effectively prevent spread of AIS from watershed to watershed or from continent to continent. But the regulations needed to prevent invasions by species such as Asian carps in North America and the United States are slow to evolve and used reluctantly by federal authorities because they are heavily influenced by regional and national political and economic considerations. State regulations, on the other hand, suffer from the influence of their own local and regional political and economic issues. Some states maintain strict policies and regulations with regard to Asian carp possession and use, but neighboring states may not. And since 48 of the 50 U.S. states are connected by a vast network of rivers, waterways, streams and roadways, invasions continue to occur and to spread. Consequently, Asian carp management in the United States is largely controlled by “least common denominator” state regulation that applies in a given watershed and beyond. This paper presents an overview of Asian carp regulations in the 50 U.S. states and offers suggestions for improved regulations.

Invasive Asian Carps in North America

<em>Abstract</em>.—The Chicago Sanitary and Ship Canal is a 50 km-long, man-made canal that connects the Great Lakes and Mississippi River drainages. The canal, which is important for navigation and storm and wastewater drainage, forms an aquatic pathway for nonnative aquatic species to spread between these two major Midwestern ecosystems. Construction of the Chicago Sanitary and Ship Canal aquatic nuisance species dispersal barrier was authorized by the National Invasive Species Act of 1996. The barrier currently consists of a micropulsed DC electric array. A demonstration barrier began operation in April 2002 and is nearing the end of its design life; a larger, longer lasting barrier is now under construction. The demonstration barrier has been effective in repelling radio-tagged common carp <em>Cyprinus carpio </em>and is expected to have similar effectiveness on other large fish. The new more powerful barrier will be more effective in repelling small fish. In the near term, addition of alternative technologies such as acoustic bubble arrays may augment effectiveness of the electric barrier. In the long term, separation of the Lake Michigan and Mississippi River drainages will provide the surest means of preventing the range expansion of aquatic invasive species via this pathway. Funding, authorization and existing waterway uses will continue to challenge development of a fully effective barrier system.

Invasive Asian Carps in North America

<em>Abstract</em>.—In the 1970s, commercial fishers reported sightings of grass carp <em>Ctenopharyngodon idella </em>in large rivers and associated backwaters of Louisiana; the first specimen in Louisiana Department of Wildlife and Fisheries’ fishery independent sampling was recorded in 1976. Beginning in the early 1980s, commercial fishers noted increasing populations of bighead carp <em>Hypophthalmichthys nobilis </em>and silver carp <em>H. molitrix </em>(together, the bigheaded carps). Populations of bigheaded carps appear to be increasing at a much slower rate than in the Midwest¸ possibly due to limited suitability of and access to backwater habitat for juvenile fish. In 2002, harvester reports of sporadic captures of “different-looking” grass carp indicated the possible presence of black carp <em>Mylopharyngodon piceus</em>. Because both normal diploid and triploid (in which triploidy has been induced to cause sterility) black carp have been stocked in the Mississippi basin, determination of the ploidy (number of chromosome sets) of these fishes is important. Since 2002, postmortem ploidy determinations using cells from eyeballs removed from six wild black carp captured in Louisiana showed each to be a normal diploid, indicative of breeding capability and potential reproducing populations. Although reported commercial landings of grass and bigheaded carps have been as high as 34,830 kg/year, limited market demand in past years resulted in many captures being discarded. A protocol for obtaining samples for easily determining ploidy is reported here. Accurate data on Asian carp distributions and their reproductive potential provides information to fisheries researchers that will be constructive in documenting the spread of these invasive species and in the assessment of risk to habitats.

Invasive Asian Carps in North America

<em>Abstract</em>.—Numerous natural resource agency and media reports have alleged that Asian carps were introduced into the wild through escapes from commercial fish farms. This chapter traces the chronology associated with importations of Asian carps to North America and discusses the likeliest pathways of their introduction to the wild. The U.S. Fish and Wildlife Service first imported an Asian carp species, grass carp <em>Ctenopharyngodon idella</em>, in 1963. Since then, state and federal agencies, universities, and private fish farmers have interacted to import Asian carps, to develop production technologies, and to promote their use in both public and private sectors in a number of different states. These importations and stocking, whether in confinement or, in the case of the grass carp, sometimes in open waters, were purposeful and legal. Asian carps were introduced to take advantage of their unique food preferences (planktivory by silver carp <em>Hypophthalmichthys molitrix </em>and bighead carp <em>H. nobilis</em>, herbivory by grass carp, and molluscivory by black carp <em>Mylopharyngodon piceus</em>). The first known accidental release of diploid grass carp was in 1966 by the U.S. Fish and Wildlife Service in Stuttgart, Arkansas. Other early reports of grass carp in the wild were from waters in Alabama, Georgia, and Florida. Grass carp were reported from the wild in 1970, 2 years before the first private hatchery received grass carp. By 1972, grass carp had been stocked in open water systems in 16 different states. Silver carp and bighead carp were first imported purposely by a commercial fish producer in Arkansas in 1973. All silver and bighead carps were transferred to the Arkansas Game and Fish Commission by March 1974 where they first successfully spawned silver carp and bighead carp later that year. The first report of silver carp in the wild was in Arizona in 1972, although strong evidence suggests that this may have been a misidentification, followed by reports in Arkansas in the wild in 1975. The Arkansas report occurred 2 years before bighead carp and silver carp were returned to private hatcheries for commercial production. By 1977, silver carp and bighead carp had been introduced to Alabama, Arizona, Arkansas, Illinois, and Tennessee. Research and stockings of silver carp and bighead carp were conducted by at least six state and federal agencies and three universities in seven states in the 1970s and 1980s. Public-sector agencies, which were successful in encouraging development and use of Asian carps that today are in commercial trade, are the likeliest pathways for the earliest escapes of grass carp, silver carp, and bighead carp.

Invasive Asian Carps in North America

<em>Abstract</em>.—Our book <em>The Black Carp: Biological Synopsis and Risk Assessment of an Introduced Fish </em>was published in 2005. The present chapter provides a brief overview of new events and re-examines pieces of earlier information on this molluskeating species. Effective November 19, 2007, black carp <em>Mylopharyngodon piceus </em>was placed on the Lacey Act list of injurious wildlife. Listing pertains to all forms of live black carp, including diploids (reproductively fertile), triploids (thought to be sterile), hybrids, and gametes and viable eggs, prohibiting their import into the United States and banning interstate transport. States retain rights to regulate black carp already within their jurisdiction. Although many states now ban black carp, a few states in the lower Mississippi basin still permit breeding programs and allow use of black carp for snail control in ponds. In North America, black carp are present in open waters of the lower Mississippi River basin. Likely the result of escape from aquaculture, some captures reportedly date to the early 1990s. Most (10 of 11) wild captures tested have been found to be diploids. During the mid-1990s, an estimated 400,000 black carp were in aquaculture. The number fluctuates and present total is uncertain but includes diploids. Currently, it is not possible to adequately assess the risk of additional escape because the numbers and distribution of diploid and triploid black carp held in aquaculture and the frequency and intensity of farm-pond flooding are not fully documented. Much also remains unknown about wild black carp populations in the Mississippi basin, especially with regard to their distribution, abundance, reproduction status, and types of mollusk prey consumed. The paucity of data is largely attributed to the difficulty of capturing wild black carp and the near absence of field research targeting this species.