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.

Hypomesus nipponensis
Hypomesus nipponensis

Copyright Info
Hypomesus nipponensis McAllister, 1963

Common name: wakasagi

Taxonomy: available through www.itis.govITIS logo

Identification: Moyle (1976a); Page and Burr (1991).

Size: 17 cm.

Native Range: Japan (Page and Burr 1991).

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

Nonindigenous Occurrences:

Table 1. States with nonindigenous occurrences, the earliest and latest observations in each state, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Hypomesus nipponensis are found here.

StateFirst ObservedLast ObservedTotal HUCs with observations†HUCs with observations†
CA1959201416Honey-Eagle Lakes; Lower American; Lower Klamath; Lower Sacramento; Madeline Plains; Mad-Redwood; Mojave; North Fork Feather; Santa Ana; Santa Margarita; Shasta; Suisun Bay; Upper Bear; Upper Cosumnes; Upper Sacramento; Upper Yuba

Table last updated 3/2/2024

† Populations may not be currently present.

Means of Introduction: Wakasagi were intentionally introduced in 1959 from Japan by the California Department of Fish and Game as an experimental forage fish for trout (Wales 1962; Moyle 1976b; Dill and Cordone 1997).

Status: This species is established in several reservoirs and associated tributaries in California (Moyle 1976a; Shapovalov et al. 1981; Courtenay et al. 1986). It has not been recorded in Big Bear Lake since 1960 (Swift et al. 1993).

Impact of Introduction: This species has been found to negatively impact kokanee Oncorhynchus nerka and threadfin shad Dorosoma petenense (Dill and Cordone 1997). It also is known to hybridize with the native and federally endangered delta smelt Hypomesus transpacificus. Hybridization between the two species was suspected by Courtenay et al. (1986), and was later confirmed (Dill and Cordone 1997; Trenham et al. 1998).

Remarks: Dill and Cordone (1997) reviewed its introduction history in California. In documenting the original introduction, Wales (1962) incorrectly identified the species as Hypomesus olidus. Several authors (e.g., Moyle 1976a; Lee et al. 1980 et seq.) treated the introduced wakasagi as a subspecies of H. transpacificus (i.e., as H. t. nipponensis). In California the wakasagi is generally considered a freshwater species, hence its often-used name "freshwater smelt" in that state; however, it has recently been discovered in brackish waters, further threatening the continued survival of the imperiled delta smelt (Dill and Cordone 1997).

References: (click for full references)

Courtenay, W. R., Jr., D. A. Hensley, J. N. Taylor, and J. A. McCann. 1984. Distribution of exotic fishes in the continental United States. Pages 41-77 in W. R. Courtenay, Jr., and J. R. Stauffer, Jr., editors. Distribution, biology and management of exotic fishes. Johns Hopkins University Press, Baltimore, MD.

Courtenay, W. R., Jr., D. A. Hensley, J. N. Taylor, and J. A. McCann. 1986. Distribution of exotic fishes in North America. Pages 675-698 in C. H. Hocutt, and E. O. Wiley, editors. The zoogeography of North American freshwater fishes. John Wiley and Sons, New York, NY.

Dill, W.A., and A.J. Cordone. 1997. History and status of introduced fises in California, 1871-1996. Calilfornia Department of Fish and Game. Fish Bulletin 178.

Lee, D. S., C. R. Gilbert, C. H. Hocutt, R. E. Jenkins, D. E. McAllister, and J. R. Stauffer, Jr. 1980 et seq. Atlas of North American freshwater fishes. North Carolina State Museum of Natural History, Raleigh, NC.

Matern, S.A., P.B. Moyle, and L.C. Pierce. 2002. Native and alien fishes in a California estuarine marsh: twenty-one years of changing assemblages. Transactions of the American Fisheries Society. 131: 797-816.

Moyle, P. - University of California, Davis.

Moyle, P. B. 1976a. Inland fishes of California. University of California Press, Berkeley, CA.

Page, L. M., and B. M. Burr. 1991. A field guide to freshwater fishes of North America north of Mexico. The Peterson Field Guide Series, volume 42. Houghton Mifflin Company, Boston, MA.

Shapovalov, L., A. J. Cordone, and W. A. Dill. 1981. A list of freshwater and anadromous fishes of California. California Fish and Game 67(1):4-38.

Sommer, T, B. Harrell, M. Nobriga, R. Brown, P. Moyle, W. Kimmerer, and L. Schemel. 2001. California's Yolo Bypass: Evidence that flood control can be compatible with fisheries, wetlands, wildlife, and agriculture. Fisheries. American Fisheries Society. 26 (8): 6-16.

Swift, C. C., T. R. Haglund, M. Ruiz, and R. N. Fisher. 1993. The status and distribution of the freshwater fishes of southern California. Bulletin of the Southern California Academy of Science 92(3):101-167.

Trenham, P.C., H.B. Shaffer, and P.B. Moyle. 1998. Biochemical identification and assessment of population subdivision in morphologically similar native and invading smelt species (Hypomesus) in the Sacramento-San Joaquin Estuary, California. Transactions American Fisheries Society 127:417-424.

Wales, J. H. 1962. Introduction of pond smelt from Japan to California. California Fish and Game 48(2):141-142.

FishBase Summary

Author: Fuller, P.

Revision Date: 9/16/2011

Peer Review Date: 9/16/2011

Citation Information:
Fuller, P., 2024, Hypomesus nipponensis McAllister, 1963: U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, https://nas.er.usgs.gov/queries/FactSheet.aspx?speciesID=794, Revision Date: 9/16/2011, Peer Review Date: 9/16/2011, Access Date: 3/2/2024

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.


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Citation information: U.S. Geological Survey. [2024]. Nonindigenous Aquatic Species Database. Gainesville, Florida. Accessed [3/2/2024].

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