Aristichthys nobilis (Richardson, 1845), Leuciscus nobilis Richardson, 1845

Distinguishing characteristics were given in Berg (1949) and Jennings (1988). Distinguishing characteristics, along with keys that include this species and photographs or illustrations also were included in a few of the more recently published state fish books (e.g., Robison and Buchanan 1988; Etnier and Starnes 1993; Pflieger 1997). A commonly used name is Aristichthys nobilis. Maximum size: 40 kg and 71.6 cm (Jennings 1988).

Female bighead carp reach sexual maturity at three years of age, while males can reach sexual maturity in two years; however, this varies significantly with changing environmental conditions (Huet 1970; Kolar et al. 2007).  Bigheaded carps are only known to spawn in large, turbulent rivers and it is believed that a rising hydrograph (flood event) is a primary spawning cue (Kolar et al. 2007). Fecundity increases with age and body weight and is directly related to growth rate (Verigin et al. 1990). In its native range, Bighead Carp has a fecundity ranging from 280,000-1.1 million eggs. In North America, fecundity ranged from 4,792-1.6 million eggs (Kipp et al. 2011).  Bighead carp produce eggs that are semi-buoyant and require current to keep them from sinking to the bottom (Soin and Sukhanova 1972; Pflieger 1997).  The eggs float for 40-60 hours before hatching.

Potential pathway(s) of introduction: Dispersal, unauthorized release, and escape from commercial culture
Large populations of bighead carp are established in the middle and lower segments of the Illinois River, the upper Illinois River (Waterway), and the Chicago Area Waterway System (CAWS) (Baerwaldt et al. 2013).  Three bighead carp adults were collected in Lake Erie between 1995 and 2000, but they are not thought to represent an established population (Cudmore et al. 2012). The body condition of these individuals was healthy, but their reproductive organs were not viable (B. Cudmore, Fisheries and Oceans, pers. comm.). Bighead carp individuals have also been collected in isolated Chicago lagoons (e.g., Schiller Park Pond, Columbus Park Lagoon, Garfield Park Lagoon, McKinley Park Lake, Flatfoot Lake) closer to Lake Michigan. In 2008, a bighead carp was found in Lincoln Park South Lagoon, which connects to Lake Michigan via a screened overflow drain; this pond was poisoned and drained in late 2008 (Willink 2010).
The U.S. Army Corps of Engineers  constructed a set of three electrical barriers, the first of which opened in 2002, on the Chicago Sanitary and Shipping Canal to prevent the spread of aquatic invasive species between the Great Lakes and Mississippi River basins; only one live bighead carp has been found  (Lake Calumet in 2010) in the waterway above the barrier and a dead individual was found on the shore of Lake George, Indiana (Baerwaldt et al. 2013).

While not indicative of live fish, environmental DNA (eDNA) of bighead carp has been found in water samples collected above the electric barriers (i.e., closer to Lake Michigan) in 2012 from Lake Calumet (USACE 2012). Additional eDNA of silver carp has been found in Sandusky Bay, Lake Erie (OH) (Jerde et al. 2013).

As of 2012, there were no bigheaded carps in or near the St. Lawrence River and opportunities for the introduction of bigheaded carps to the St. Lawrence River are not well understood.  However, should they gain access to the St. Lawrence River, laker ballast water or natural dispersal would provide a direct route to Lake Ontario  (Cudmore et al. 2012).

The potential for purposeful, human-mediated releases of bigheaded carps into the Great Lakes basin does exist. Humans have illegally released freshwater fishes for sport opportunities (Crossman and Cudmore 1999a, Bradford et al. 2008) or spiritual/ethical reasons (Crossman and Cudmore 1999b, Severinghaus and Chi 1999, Shiu and Stokes 2008). This human behavior of illegally releasing nonnative fishes into the aquatic environment is difficult to characterize and quantify (Bradford et al. 2008).

Most states prohibit the use of carp as baitfish, however juvenile carp may be present as a contaminant in baitfish.  Feeder fishes (typically goldfish (Carassius auratus) or “rosy reds” (colour variant of fathead minnow (Pimephales promelas)) shipped into the Great Lakes basin could be contaminated with bigheaded carps if they originated from fish farms in the Mississippi River basin. Fathead minnows found in the bait industry in Michigan are known to originate from culture in Arkansas, Minnesota, North Dakota, and South Dakota (G Whelan, Michigan DNR, pers. comm.). However, the volume of such movement and the extent of contamination, if any, is unknown. Based on a subsample of live fish import records for 2006-2007, fathead minnows (likely rosy reds) imported for the aquarium trade originated primarily from Missouri and secondarily from North Carolina (Cudmore et al. 2012).

It is currently illegal to possess or sell live invasive carps in Ontario; however, despite this legislation, bighead carp and grass carp were documented in shipments for import into Ontario. Eight entry records were recorded from January 2010 to August 2011 that listed grass (9.8 mt) and bighead (16.8 mt) carps as species descriptions. All of the shipments originated in Arkansas.” (Cudmore et al. 2012)
There are many ponds and artificial lakes in the Chicago metropolitan area which are commonly stocked for fishing with Channel catfish (Ictalurus punctatus). Channel catfish are often purchased from southern fish farmers, where it is possible for the stock to be contaminated with juvenile bighead carp. For instance, in September 2011, 17 large bighead carp were collected from Flatfoot Lake in the Beaubien Forest Preserve (K. Irons, Illinois Department of Natural Resources, pers. comm.).  Three bighead carp were also found from Schiller Pond. Escapes of another Invasive Carp, grass carp, have occurred in similar circumstances.

Bighead carp have been able to establish themselves in a wide range of environments with a wide range of temperatures and lower salinity levels. They are moderately dietary generalists feeding on a variety of zooplankton and algae (Gollasch et al 2008).  Bighead carp have been demonstrated to outcompete both native larval fishes and mussels (Laird and Page 1996).  It would be highly likely for the bighead carp to find an appropriate food source but the amount they eat might not be sufficiently found in the Great Lakes. Recent bioenergetics models suggest that productive nearshore areas and embayments (e.g. Green Bay and the Western Basin of Lake Erie) would be able to sustain growth of Bighead and Silver carp, but these species would likely be food-limited in the oligotrophic offshore regions (Anderson et al. 2017;  Anderson et al. 2015; Cooke and Hill 2010).

Locations of bighead carp in Asia suggest that they may tolerate winter conditions in the Great Lakes.  Winter mortality is not known to be an issue for bigheaded carps in the Mississippi River basin; bigheaded carp fingerlings are collected from floodplain wetlands in the spring in years when those wetlands were not connected to the river (D. Chapman, USGS, pers. obs.). Overwinter mortality may influence the northern limits of the native range of bigheaded carps, but has not been modeled specifically for these species in North America. Ecological niche modeling predicting the potential North American distribution of bigheaded carps indicated that they could survive well north of the Great Lakes basin (Herborg et al. 2007); therefore, overwinter mortality will likely not be a limiting factor in most years (Cudmore et al. 2012

Kolar et al. (2007) stated that the limiting factor for Invasive Carp establishment in most regions of the United States would be access to a river in which Invasive Carp could successfully spawn. Bighead carp need large, turbulent rivers and higher temperatures to spawn. The eggs float for 40-60 hours before hatching. Only some Great Lakes tributaries have flows of sufficient velocity and temperature that support bighead carp reproduction, and only during parts of the year. Two studies have examined the suitability of Great Lakes tributaries for bigheaded carp spawning based on more detailed considerations of reproductive biology. Kocovsky et al. (2012) examined potential spawning habitat suitability of eight US tributaries in the central and western basins of Lake Erie. Factors considered included: the thermal conditions of the tributaries and open waters of Lake Erie, the minimum total degree-days required for bighead carp maturation, onset of carp spawning and mass spawning, the timing of flood events as triggers for spawning, and length of stream required for egg hatching based on stream velocity and estimated incubation time. Kocovsky et al (2012) concluded that three larger tributaries were thermally and hydrologically suitable to support spawning of bigheaded carps, four tributaries were less suited, and one was ill suited. Mandrak et al. (2011) conducted a similar analysis for the 25 Canadian tributaries of the Great Lakes. They concluded suitable spawning conditions were present in nine of 14 tributaries to Lake Superior with sufficient data; however, only one of the nine tributaries had a mean annual total degree-days exceeding 2,685. Therefore, bigheaded carps are unlikely to mature within Lake Superior tributaries, but may encounter sufficient growing degree-days to mature in some parts of Lake Superior such as near shore and bays. Further analysis is required to identify such areas. Mandrak et al. 2011 concluded suitable spawning conditions for bighead carp, including growing degree-days required for maturation, were present in 23 of 27 tributaries to Lake Huron, nine of 10 tributaries to Lake Erie, and 16 of 28 tributaries to Lake Ontario. These analyses suggest that access to tributaries with suitable thermal and hydrologic regimes in the Great Lakes should not limit spawning by bigheaded carps (Cudmore et al. 2012). Additionally, Cuddington et al. (2014) found that establishment would be likely for a small number of founding individuals (<20 fish) despite environmental stochasticity. Furthermore, the presence of only a few suitable spawning rivers on each lake may promote establishment success given that the carp would have an increased chance of finding a mate in the relatively few nearby spawning rivers. However, establishment becomes less likely if age of first sexual reproduction is substantially delayed.

Summary of species impacts derived from literature review. Click on an icon to find out more...

Environmental	Socioeconomic	Beneficial

Bighead Carp are powerful filter-feeders that grow fast and reproduce quickly , which makes this species a strong competitor with all local fish species because most fish in early life-stages consume plankton (Xie and Chen 2001). These fish are capable of significantly reducing zooplankton abundance, which adversely affects planktivorous early life stages of other fish species (Chick et al. 2001, Xie and Chen 2001). Bigheqad carp fish are known to decrease the size of zooplankton within a species (Radke and Kahl 2002; Kim et al. 2003). Hypophthalmichthys spp. also can alter species composition in phytoplankton communities by promoting the dominance of species that can resist digestion (Görgényi et al. 2016). It seems likely that Hypophthalmichthys spp. have the potential to alter the food web in ways that could negatively affect fishes such as native planltivores (Kolar et al. 2005, Wang et al. 2018, Love et al. 2018). Furthermore, bighead carp compete with fish that are filter-feeders as adults. Several studies have shown that when zooplankton biomass is limiting, bighead carp have a competitive advantage over native species, such as bluegills, bigmouth buffalo, and gizzard shad (Schrank et al. 2003, Schrank and Guy 2003, Irons et al. 2007, Wang et al. 2018, Zhou et al. 2020).

Bighead carp is host the gill-damaging anchorworm (Lernaea cyprinacea) and the invasive carp tapeworm (Scyzocotyle acheilognathi)  While bighead carp are minimally affected by these parasites, they have the potential of spreading and affecting native fish species (Goodwin 1999, Hoole et al. 2001, Kolar et al. 2005).

Food web models of Saginaw Bay Lake Huron, Lake Ontario, Lake Michigan and Lake Erie have suggested that invasive carp impacts on the Great Lakes ecosystem might be mitigated by several factors and trophic interactions such as the availability of unused production that might be exploited by the carp, increased production at lower trophic levels due to high nutrients, and the potential for native piscivores to feed on larval invasive carp (Zhang et al. 2016; Currie et al. 2012, Kao et al 2018;  Ivan et al. 2020; Rutherford et al 2021).

Hypophthalmichthys nobilis has a high potential socio-economic impact in the Great Lakes.

The spread of bighead carp in the Mississippi River Basin has negatively impacted commercial fishing (Maher 2005). These carp now make up a significant portion of the catch, while the harvest of other species declined. The large number of bighead carp caught and their higher average weight compared to other species may pose a threat to the sustainability of commercial fishing. The establishment of economically viable markets could be crucial in managing the bighead carp population and mitigating its impact on the fishing industry in the United States (Conover et al. 2007, Kolar et al. 2007).

The diet of this species overlaps with that of planktivorous species (fish and invertebrates) and the young of virtually all native fishes. Competition could lead to the decline of native species that are important as sport and food species are bound to have a negative economic impact on recreational angling and other industries that benefit from sport fishing (Kolar et al. 2005).

Hypophthalmichthys nobilis has the potential for high beneficial effects if introduced to the Great Lakes.

Bighead carp is a popular food fish in its native China and several other countries, ranking fourth in 1999 in world aquaculture production (FAO 1999). Although not so popular in North America, commercial fisheries for bighead carp exist on the Mississippi, Missouri, and Illinois rivers and are sold from small specialty food markets to consumers of various Asian cultures in major North American cities (Conover et al. 2007, Kolar et al. 2005, Stone et al. 2000). Nonetheless, the market for live bighead carp in the United States is limited (the typical consumer will buy only enough fish for the current day’s meal) and easily saturated.
Bighead carp are frequently used in polyculture with other fish, such as common carp, various tilapias, largemouth bass, and bigmouth buffalo (Jennings 1988) to control zooplankton and phytoplankton populations (Conover et al. 2007).

Additionally, bighead carp can be an important source of revenue for catfish farmers during times of low catfish prices (Stone et al. 2000).  Engle and Brown (1998) estimated that the net benefit of stocking bighead carp with catfish was substantially higher. Net benefits ranged from $1,628 to $2,743 annually from a 6-ha (15-acre) pond. Furthermore, there is evidence of bighead carp used as sport fish in Oklahoma. Relatively numerous sport fishing catches have been recorded downstream from a low-water dam in the Neosho River at Miami, Oklahoma (Jester et al. 1992).

The role of bighead carp as a biological control agent for plankton control and removal is largely debated.  While Henderson (1978, 1983) suggested that both bighead and silver carps would stimulate phytoplankton blooms that would result in removal of nutrients by phytoplankton, Opuszynski (1980) found that organic carbon, nitrogen, and total phosphorus increased in bottom sediments, despite the decrease in nitrogen, phosphorous, and dissolved. When those bottom sediments were disturbed by activities of other fishes, phytoplankton populations increased. Furthermore, Lieberman (1996) stocked bighead and silver carps and found that total phosphorus and total inorganic nitrogen increased as a result. Yet, some studies have reported that bighead carp is able to improve water quality by continually removing plankton, especially blue-green algae. This stabilizes plankton and lessens the probability of die-offs in production ponds (Kolar et al. 2007, Schofield et al. 2005).

Use of carp as bait is prohibited in MN, WI, IN, MI, NY, Ontario, and Quebec; with Michigan and Ontario specifically prohibiting the use of “Asian carps.” (Cudmore et al. 2012).  The Invasive Carp working group recommends development of certification program(s) for baitfish to be disease-free and uncontaminated by nonindigenous species (Conover et al 2007).

Control
The Aquatic Nuisance Species Task Force and the U.S. Fish and Wildlife Service organized an Invasive Carp Working Group (Working Group) to develop a comprehensive national Invasive Carp management and control plan. The Working Group agreed that the desired endpoint of the plan is the extirpation of Invasive Carps (bighead, silver, black and grass) in the wild, except for non-reproducing grass carp within planned locations (Conover et al 2007).

Monitoring of the Chicago Area Waterways System (including the Chicago Sanitary and Shipping Canal) supporting early detection allowing for rapid response is a key component of efforts to control the spread of Hypophthalmichthys nobilis from the Mississippi River system into the Great Lakes. 

Biological
Safe and effective biological control of bighead carp is not yet feasible.  Several potential technologies are being explored including: release of sterile male fish, triploid carp, transgenic alternatives (daughterless carp and Trojan genes), pheromones (sex lures or juvenile aggregation for traps), disease agents, parasites, predators.

Physical
Many types of physical barriers are being examined for potential to stop the dispersal of Invasive Carp including Hypophthalmichthys nobilis.  These include earth berms, fences, electric barriers, bubble curtains, acoustic barriers, strobe lights and high pressure sodium lights.  

The electrical fish barrier can function either as an impassable barricade or as a fish guidance system.   In either case, the system consists of a series of metal electrodes submersed in water to create an electrical field capable of repelling fish. Electrical barriers have been evaluated for preventing the expansion of feral Invasive Carp populations in both the Chicago Sanitary and Ship Canal and the Upper Mississippi River System. While considered feasible for the Chicago Sanitary and Ship Canal, it was determined that electrical barriers would be less effective and less feasible on the Upper Mississippi River System. The U.S. Army Corps of Engineers (USACE) constructed a set of three electrical barriers, the first of which opened in 2002, on the Chicago Sanitary and Shipping Canal to prevent the spread of aquatic invasive species between the Great Lakes and Mississippi River basins.  Although currently in use, electric barriers are not the end-all solution to the range expansion of feral Invasive Carps in the United States. Electric barriers are not selective as to species affected.

The bubble curtain is the most elementary form of behavioral fish barrier,  which in its simplest form consists of a perforated tube laid across a river bed through which compressed air is forced. The rising curtain forms a wall of bubbles that can deflect fish.   Efficacy of the bubble curtain may be enhanced when combined with light or sound. Acoustic barriers have shown promise in research trials. Bighead and silver carps have acute hearing and are sensitive to frequencies outside the range of many native species. Thus, an acoustic array could be designed such that it primarily affects bighead and silver carps and has less effect on non-target species.  The Invasive Carp working group recommends development of redundant barrier systems within the Chicago Sanitary and Ship Canal, including acoustic bubble curtains (Conover et al 2007).
In addition to the Chicago Sanitary and Ship Canal, the Great Lakes Regional Collaboration Aquatic Invasives Species Strategy Team Action Plan (USEPA 2005) identifies the Ohio canals and waterways system as priority interbasin connections that must be addressed to prevent the spread of Invasive Carps into the Great Lakes. Particular attention should be directed to the Ohio and Erie and Miami and Erie canals. The potential for spread of  Invasive Carps from the Ohio River Basin into the Great Lakes via these routes is significant (Conover et al 2007).  The Great Lakes and Mississippi River Interbasin Study (USACE 2014) includes site-specific analysis for 18 of these other aquatic pathways for dispersal between the two basins and makes specific recommendations for each.

High pressure sodium lights (1,000 watts) have been used to attract and hold fish to slow water areas located near a powerhouse spillway.   Mercury lights have also been used as attractants for species-specific applications. Attractants may be used in combination to congregate fish that are avoiding other behavioral barriers or deterrents.  The strobe light has been extensively evaluated as a fish deterrent in both laboratory and field situations and has been used in conjunction with other behavioral devices to increase the level of fish diversion. Combinations with bubble curtains may enhance the  effectiveness of both, as the light can be projected onto the bubble sheet. Strobe lights can repel fish by producing an avoidance response.

Increasing the commercial and recreational harvest of Invasive Carps in the Mississippi River basin is an important component of the strategy for preventing the spread of these fishes to the Great Lakes.  Reducing population size, particularly in waterways near the Great Lakes, reduces propagule pressure.  The effects of Invasive Carps on native ecosystems are likely to be proportional to their abundance, thus reducing population size can also be an important component of efforts to minimize impact (Conover et al 2007).

Chemical
The toxicity of many chemicals to bighead, grass, and silver carps has been examined (13 chemicals, 34 studies for bighead carp; 75 chemicals, 233 studies for grass carp; 21 chemicals, 83 studies for silver carp; Pesticide Action Network 2005).  Rotenone and antimycin are the only registered piscicides available to potentially control Invasive Carps in the United States without considerable additional expense. Rotenone and antimycin are both labeled for use in lakes and running waters (i.e., streams and rivers). The American Fisheries Society has published a manual for the use of rotenone in fisheries management (Finlayson et al. 2000). Research is needed to further investigate the effectiveness of registered piscicides to control Invasive Carps, evaluate their potential use in the control of feral populations, and to determine the potential of other chemicals to control Invasive Carps.

Other
The Invasive Carp Working Group recommends development of a decision support system to prioritize locations for barriers to carp dispersal.

Voucher specimens: Florida (UF 98162).