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The Nonindigenous Occurrences section of the NAS species profiles has a new structure. The section is now dynamically updated from the NAS database to ensure that it contains the most current and accurate information. Occurrences are summarized in Table 1, alphabetically by state, with years of earliest and most recent observations, and the tally and names of drainages where the species was observed. The table contains hyperlinks to collections tables of specimens based on the states, years, and drainages selected. References to specimens that were not obtained through sighting reports and personal communications are found through the hyperlink in the Table 1 caption or through the individual specimens linked in the collections tables.

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Common name: Koi

Synonyms and Other Names: Cyprinus carpio Linnaeus, 1758; Cyprinus carpio haematopterus; Koi carp; nishikigoi; Amur carp; East Invasive Carp

Taxonomy: available through www.itis.gov

Identification: Koi are a domesticated ornamental carp taxa that vary widely in coloration with combinations of bright gold, orange, silver, white, and black colors patterns (Kottelat and Freyhof 2007). Koi are characterized by their deep body, two barbels on each side of its upper jaw, and serrated dorsal spine (Nelson 1984).

Koi (Cyprinus rubrofuscus) are ornamental varieties of domesticated carp that are often erroneously identified as European Carp (C. carpio) (Kottelat and Freyhof 2007). Wild C. rubrofuscus can be distinguished from wild C. carpio by having 29-33 + 2-3 lateral line scales (vs. 33-37 + 2-3), 18-22.5 branched dorsal rays (vs. 17-20.5), a silvery body with red pelvic, anal, and lower caudal lobes (vs. grey to bronze) (Kottelat and Freyhof 2007).

Size: 30 to 60 cm long (Tomelleri and Eberle 1990)

Native Range:

Alaska	Hawaii	Puerto Rico & Virgin Islands	Guam Saipan

Hydrologic Unit Codes (HUCs) Explained
Interactive maps: Point Distribution Maps

Ecology: Koi are long-lived and have a typical life span of around 40 years, but the oldest-known koi lived to be 230 years old. They reach sexual maturity around age 4 and breed yearly thereafter (Smithsonian National Zoo and Conservation Biology Institute 2019).

Impact of Introduction: Disease

Koi carry and transmit the koi herpesvirus (KHV) disease, which can result in large die-offs of many carp groups (Matsui et al. 2008). The species is also capable of becoming infected with carp oedema virus (CEV), which causes koi sleepy disease (KSD) and results in sickness and the eventual death of the fish from anoxia, which can affect the ornamental koi industry, as there is a 100% motality rate for the disease (Kim et al. 2017).

Remarks: Taxonomy

The koi has gone through a lot of taxonomic changes due to extensive cultivation and breeding history (Gross et al 2002; Zhou et al 2003a), and its origins are uncertain, leaving its taxonomic status ambiguous (Dong et al. 2015). Gross et al (2002) found koi to be a distinct monophyletic group resulting from domestication, but more closely related to East Invasive Carp groups, and recognized as the subspecies Cyprinus carpio haematopterus; this was also the conclusion and taxonomic assignment in similar studies from the same time period that used allozyme data (Kohlmann and Kersten 1999; Zhou et al 2013b). Literature from a decade later has also recognized koi as carp subspecies Cyprinus carpio haematopterus (Kim et al 2018; Zoran et al 2017). Matsui et al (2008) recongnized koi as a carp subspecies Cyprinus carpio koi. Athough Zhou et al (2003b) used the subspecies name rubrofuscus to describe other carp strains, Eschmeyer’s Catalog of Fishes, as well as the Integrated Taxonomic Information System (ITIS),  recognizes the species Cyprinus rubrofuscus as of June 2019 (Fricke et al 2019), putting a lot of the other subspecies assigned to the koi as synonyms (Dong et al. 2015).

References: (click for full references)

Dong, C., J. Xu, B. Wang, J. Feng, Z. Jeney, X. Sun, and P. Xu. 2015. Phylogeny and evolution of multiple common carp (Cyprinus carpio L.) populations clarified by phylogenetic analysis based on complete mitochondrial genomes. Marine Biotechnology 17(5):565-575.

Fricke, R., W. N. Eschmeyer, and R. Van der Laan. 2019. Eschmeyer's Catalog of Fishes: Genera, species, references. http://researcharchive.calacademy.org/research/ichthyology/catalog/fishcatmain.asp. Accessed on 06/26/2019.

Gross, R., K. Kohlmann, and P. Kersten. 2002. PCR–RFLP analysis of the mitochondrial ND-3r4 and ND-5r6 gene polymorphisms in the European and East Asian subspecies of common carp (Cyprinus carpio L.). Aquaculture 204:507-516.

Kim, S.W., J.W. Jun, S.S. Giri, C. Chi, S. Yun, H.J. Kim, S.G Kim, J.W. Kang, and S.C. Park. 2017. First report of carp oedema virus infection of koi (Cyprinus carpio haematopterus) in the Republic of Korea. Transboundary and Emerging diseases 00:1-6.

Kohlman, K., and P. Kersten. 1999. Genetic variability of German and foreign common carp (Cyprinus carpio L.) populations. Aquaculture 173:435-445.

Kottelat, M., and J. Freyhof. 2007. Handbook of European freshwater fishes. Publications Kottelat, Cornol, Switzerland.

Matsui, K., M. Honjo, Y. Kohmatsu, K. Uchii, R. Yonekura, and Z. Kawabata. 2008. Detection and significance of koi herpesvirus (KHV) in freshwater environments. Freshwater Biology 53:1262-1272.

Nelson, J.S. 1984. Fishes of the World, 2nd Edition. John Wiley & Sons New York.

Popovski, Z., K. Kwasek, M. Wojno, K. Dabrowski, and M. Wick. 2017. Identification and partial characterization of a sex specific protein in Koi carp (Cyprinus carpio haematopterus). Acta Veterinaria-Beograd 67(2):285-291.

Smithsonian National Zoo and Conservation Biology Institute. 2019. Japanese koi. https://nationalzoo.si.edu/animals/japanese-koi. Accessed on 06/27/2019.

Tomelleri, J., M. Eberle. 1990. Fishes of the Central United States. Lawrence, Kansas: University Press of Kansas.

Zhou, J., Z. Wang, Y. Ye, and Q. Wu. 2003b. PCR-RFLP analysis of mitochondrial DNA ND5/6 region among 3 subspecies of common carp (Cyprinus carpio L.) and its application to genetic discrimination of subspecies. Chinese Science Bulletin 48(5):465-468.

Zhou, J., Q. Wu, Y. Ye, and J. Tong. 2003a. Genetic divergence between Cyprinus carpio carpio and Cyprinus carpio haematopterus as assessed by mitochondrial DNA analysis, with emphasis on origin of European domestic carp. Genetica 119:93-97.

Other Resources:
US Fish and Wildlife Service Ecological Risk Screening Summary for Cyprinus rubrofuscus

Author: Daniel, W. M., Morningstar, C.R., and Procopio, J.

This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.