NAS logo - click to go to the NAS home page Fish (Phylum Chordata, Subphylum Vertebrata) are found in all types of aquatic environments, from fresh to salt water. Common methods of introduction include intentional and accidental stocking, release of bait fish, release of unwanted aquarium fish, escape from aquaculture facilities, and discharge of ballast water. Potential impacts include competition with native species for food and habitat, reduction of natives by predation, transmission of diseases or parasites, and habitat alteration. One example is the inland silversides, Menidia beryllina, which was illegally introduced into Clear Lake, California, as a nutrient reservoir for bluegreen algae blooms and to reduce the Clear Lake gnat and chironomid midge populations. As a result of this introduction, the silversides have competitively displaced several native fish species, including the now extinct Clear Lake splittail.
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Data Queries and Species Lists

Fish Picture Data Queries
Species List of Nonindigenous Fish
(links to species profiles and collection information)

Links to News and Other Information

Snakehead Biological Synopsis and Risk Assessment (2004) (PDF, 7.60 MB*)

*Note: Links marked with an asterisk (*) are in PDF format. Adobe Acrobat Reader or similar software is required to view these documents.


The data represented on this site vary in accuracy, scale, completeness, extent of coverage and origin. It is the user's responsibility to use these data consistent with their intended purpose and within stated limitations. We highly recommend reviewing metadata files prior to interpreting these data.

Citation information: U.S. Geological Survey. [2024]. Nonindigenous Aquatic Species Database. Gainesville, Florida. Accessed [7/19/2024].

Contact us if you are using data from this site for a publication to make sure the data are being used appropriately and for potential co-authorship if warranted.

For general information and questions about the database, contact Wesley Daniel. For problems and technical issues, contact Matthew Neilson.