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.

Metriaclima zebra
Metriaclima zebra
(Nyassa blue cichlid)

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Metriaclima zebra (Boulenger, 1899)

Common name: Nyassa blue cichlid

Synonyms and Other Names: blue mbuna, Nyassa blue cichlid

Taxonomy: available through www.itis.govITIS logo

Identification: According to Eccles and Trewavas (1989), the genus Pseudotropheus is in particular need of revision and critical appraisal. Pseudotropheus zebra alone represents a complex of about 27 species (Ribbink et al. 1983). Some distinguishing characteristics of the species complex, a description of color patterns, figures, and photographs were given by Ribbink et al. (1983). Color photographs of various species and morphs were given in Ribbink et al. (1983), Axelrod et al. (1985), Lewis et al. (1986), and Axelrod (1993); also see illustrations in Petrovicky (1988). Size varies among members of the complex, with maximum size ranging from about 6 to 14 cm (Axelrod 1993).

Size: 6 to 14 cm

Native Range: Tropical Africa. Lake Malawi.

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

Nonindigenous Occurrences: The first report of this fish in Nevada was by a member of the American Cichlid Association, who observed several specimens of the "marmalade" form of P. zebra during a visit to Rogers Spring, a tributary of Lake Mead near Overton, Clark County, in July 1981 (Courtenay and Deacon 1982). Later records from Rogers Spring included a single male fish taken on 14 November 1981 (Courtenay, personal communication), and several individuals reportedly found in 1983 (Courtenay, personal communication). These records were apparently the basis for the listing of the species in later publications as introduced but not established in Nevada (e.g., Deacon and Williams 1984; Courtenay et al. 1984, 1986, 1991; Courtenay and Stauffer 1990; Vinyard 2001).

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 Metriaclima zebra are found here.

StateFirst ObservedLast ObservedTotal HUCs with observations†HUCs with observations†
NV198120011Lake Mead

Table last updated 10/3/2023

† Populations may not be currently present.

Means of Introduction: Probable aquarium release.

Status: Reported from Nevada.

Impact of Introduction: The impacts of this species are currently unknown, as no studies have been done to determine how it has affected ecosystems in the invaded range. The absence of data does not equate to lack of effects. It does, however, mean that research is required to evaluate effects before conclusions can be made.

Remarks: This species or species complex is well known in the aquarium trade. In its native range, the true P. zebra is distributed widely in Lake Malawi and shows marked geographical variation in coloration and markings (Ribbink et al. 1983). In contrast to references given in selected published fish lists (e.g., Deacon and Williams 1984), we found no mention of P. zebra in Courtenay and Deacon (1983), a review paper on introductions into Rogers Spring, Nevada.

There are no known voucher specimens; however, a photograph is on file to support record.

References: (click for full references)

Axelrod, H. R. 1993. The most complete colored lexicon of cichlids. Tropical Fish Hobbyist Publications, Inc., Neptune City, NJ.

Axelrod, H. R., W. E. Burgess, N. Pronek, and J. G. Walls. 1985. Dr. Axelrod's atlas of freshwater aquarium fishes. Tropical Fish Hobbyist Publications, Inc., Neptune City, NJ.

Courtenay, W. - Florida Atlantic University, Boca Raton, FL.

Courtenay, W. R., Jr., and J. E. Deacon. 1982. Status of introduced fishes in certain spring systems in southern Nevada. Great Basin Naturalist 42(3):361-366.

Courtenay, W. R., Jr., and J. E. Deacon. 1983. Fish introductions in the American southwest: a case history of Rogers Spring, Nevada. Southwestern Naturalist 28:221-224.

Courtenay, W. R., Jr., and J. R. Stauffer, Jr.. 1990. The introduced fish problem and the aquarium fish industry. Journal of the World Aquaculture Society 21(3):145-159.

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.

Courtenay, W. R., Jr., D. P. Jennings, and J. D. Williams. 1991. Appendix 2: exotic fishes. Pages 97-107 in Robins, C. R., R. M. Bailey, C. E. Bond, J. R. Brooker, E. A. Lachner, R. N. Lea, and W. B. Scott. Common and scientific names of fishes from the United States and Canada, 5th edition. American Fisheries Society Special Publication 20. American Fisheries Society, Bethesda, MD.

Deacon, J. E., and J. E. Williams. 1984. Annotated list of the fishes of Nevada. Proceedings of the Biological Society of Washington 97(1):103-118.

Eccles, D. H., and E. Trewavas. 1989. Malawian cichlid fishes: the classification of some haplochromine genera. Lake Fish Movies, Herten, Germany.

Lewis, D., P. Reinthal, and J. Trendall. 1986. A guide to the fishes of Lake Malawi National Park. World Wildlife Fund, Gland, Switzerland. 71 pp.

Petrovicky, I. 1988. Aquarium fish of the world. Hamlyn, London, England.

Ribbink, A. J., B. A. Marsh, A. C. Marsh, A. C. Ribbink, and B. J. Sharp. 1983. A preliminary survey of the cichlid fishes of rocky habitats in Lake Malawi. South African Journal of Zoology (Zoology Dierkunde) 18(3):149-310.

Other Resources:
FishBase Summary

Author: Nico, L.

Revision Date: 4/30/2018

Peer Review Date: 4/21/2006

Citation Information:
Nico, L., 2023, Metriaclima zebra (Boulenger, 1899): U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, https://nas.er.usgs.gov/queries/FactSheet.aspx?SpeciesID=474, Revision Date: 4/30/2018, Peer Review Date: 4/21/2006, Access Date: 10/4/2023

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. [2023]. Nonindigenous Aquatic Species Database. Gainesville, Florida. Accessed [10/4/2023].

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