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.

Macrognathus siamensis
Macrognathus siamensis
(Spotfin Spiny Eel)

Copyright Info
Macrognathus siamensis (Günther, 1861)

Common name: Spotfin Spiny Eel

Synonyms and Other Names: peacock eel, peacock spiny eel.

Taxonomy: available through www.itis.govITIS logo

Identification: Elongate, eel-like fish with a compressed tail and a row of small spines along the back anterior to a soft-rayed dorsal fin; pectoral and anal fins present; no pelvic fins; snout is extended into a proboscis with anterior nostrils at the side (Kottelat 2001); 4-5 dark round spots on dorsal fin. Roberts (1980, 1986) provided keys to the genus. The elongated snout (or rostrum) containing tooth-bearing bony plates (Roberts 1980, 1986) distinguishes this genus from all others found in North America.

Size: To 200 mm SL (Kottelat 2001)

Native Range: Mekong basin in Laos, Thailand, Cambodia, and Vietnam; Chao Phraya basin (Rainboth 1996; Kottelat 2001).

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 Macrognathus siamensis are found here.

StateFirst ObservedLast ObservedTotal HUCs with observations†HUCs with observations†
FL200220223Big Cypress Swamp; Everglades; Florida Southeast Coast

Table last updated 7/23/2024

† Populations may not be currently present.

Ecology: Occurs in benthic habitats in slow-moving streams and canals, standing pools or reservoirs, or in freshwater wetlands. Diet includes benthic crustaceans, annelids, and insect larvae (Rainboth 1996).

Means of Introduction: Presumed aquarium release.

Status: Established in Everglades National Park and sections of adjacent freshwater canals (Shafland et al. 2008; Kline et al. 2013).

Impact of Introduction:
Summary of species impacts derived from literature review. Click on an icon to find out more...

EcologicalHuman Health

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 is found in the aquarium trade (along with other members of the genus Macrognathus); commonly used as a food fish in its native range (Rainboth 1996).

References: (click for full references)

Kline, J.L., W.F. Loftus, K. Kotun, J.C. Trexler, J.S. Rehage, J.J. Lorenz, and M. Robinson. 2013. Recent fish introductions into Everglades National Park: an unforeseen consequence of water-management? Wetlands. http://link.springer.com/article/10.1007/s13157-012-0362-0.

Kottelat, M. 2001. Fishes of Laos. WHT Publications (Pte) Ltd., Sri Lanka.

Rainboth, W.J. 1996. Fishes of the Cambodian Mekong. FAO Species Identification Field Guide for Fishery Purposes. Food and Agriculture Organization of the United Nations, Rome.

Roberts, T.R. 1980. A revision of the Asian mastacembelid fish genus Macrognathus. Copeia 1980(3):385-391.

Roberts, T.R. 1986. Systematic review of the Mastacembelidae or spiny eels of Burma and Thailand, with description of two new species of Macrognathus. Japanese Journal of Ichthyology 33(2):95-109.

Shafland, P.L., K.B. Gestring, and M.S. Stanford. 2008. Florida's exotic freshwater fishes - 2007. Florida Scientist 71(3):220-245.

FishBase Summary

Author: Pam Fuller, and Matt Neilson

Revision Date: 8/23/2019

Peer Review Date: 4/30/2013

Citation Information:
Pam Fuller, and Matt Neilson, 2024, Macrognathus siamensis (Günther, 1861): U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, https://nas.er.usgs.gov/queries/FactSheet.aspx?SpeciesID=2261, Revision Date: 8/23/2019, Peer Review Date: 4/30/2013, Access Date: 7/23/2024

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.


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 [7/23/2024].

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.