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Upper Midwest Environmental Sciences Center

A Biological Synopsis and Risk Assessment of Asian Carps of the Genus Hypophthalmichthys

The genus Hypophthalmichthys includes three species of bigheaded carps: bighead carp (H. nobilis), silver carp (H. molitrix), and largescale silver carp (H. harmandi). Silver and bighead carps were originally imported into the United States by the aquaculture industry in Arkansas in the early 1970s for biocontrol of algal blooms in aquaculture facilities and as culture species for human consumption. Both species subsequently escaped from aquaculture and have become established in a large portion of the middle and lower Mississippi River drainage and continue to spread throughout the basin. In only 10 years since first detection in the Missouri, Mississippi, and Illinois Rivers, these species have become the most abundant fishes in some areas of the watershed. Where abundant, these large fishes are considered a nuisance to the commercial fishing industry because they foul and destroy fishing nets. Ecological effects of these fishes have not been well documented to date. It is not believed that largescale silver carp have been introduced into the United States yet.

Silver carp
Bighead carp
Two species of Hypophthalmichthys are presently established in the United States. Both of these species, (A) silver carp (H. molitrix) and (B) bighead carp (H. nobilis), typically reach 50 pounds, consume mostly plankton, require flowing water to reproduce, and may compete with native planktivores such as paddlefish (Polyodon spathula ) and buffalo (Ictiobus sp.) fishes (illustrations by Matt Thomas).

The objectives of this study include (1) completing biological synopses for all three species of Hypophthalmichthys including taxonomy, native distribution and habitat preferences, biology and natural history, associated diseases and parasites, the history of invasions around the world and within the United States, human uses for the species, potential range within the United States, and regulations at the state level that presently pertain to each species; and (2) evaluating the organism risk potential for Hypophthalmichthys in the United States.

USA (map)
The biological risk assessments of bighead carp (Hypophthalmichthys nobilis), silver carp (H.molitrix), and largescale silver carp (H. harmandi) being conducted by scientists at the Upper Midwest Environmental Sciences Center will examine the risk that each of these species pose to water bodies throughout the United States.

Data for the biological synopsis are being obtained through searches of peer-reviewed and gray literature, the Internet, and personal communication with knowledgeable professionals. Methods outlined in a generic risk analysis process for nonindigenous aquatic organisms are being used to conduct the organism risk assessments. This process assesses the risk posed by specific pathways by which individuals of the species of concern may be introduced into U.S. waters.

In addition to providing a much needed synopsis of the biology of these species and an assessment of the environmental risks posed by them, results of this work will be used by the U.S. Fish and Wildlife Service (USFWS) to help determine whether the threat posed by either the silver or bighead carp warrants listing either species under the ‘injurious wildlife’ provisions of the Lacey Act (18 USC 42).

This project is a collaboration with Walt Courtenay, Christine Housel, and Jim Williams of the U.S. Geological Survey Florida Integrated Science Center, Gainesville, Florida; Duane Chapman of the U.S. Geological Survey Columbia Environmental Research Center; and Dawn Jennings of the USFWS North Florida Field Office. The project will be completed in three stages. Stage one, a Lacey Act evaluation criteria technical assistance document to the USFWS was completed in April 2004; stage two, a draft biological synopsis and risk assessment technical assistance document to the USFWS was completed in August 2004. The final stage of the project is to finalize the biological synopsis and risk assessment document, to have it peer reviewed, and to have it published in the form of a special publication by the American Fisheries Society.

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