Myloplus rubripinnis
Myloplus rubripinnis
(redhook pacu)
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Exotic
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Trisha M. Shears (commons.wikimedia.org) Copyright Info
Myloplus rubripinnis (Müller and Troschel, 1844)
Common name: redhook pacu
Synonyms and Other Names: Myleus rubripinnis (Müller and Troschel, 1844)
Taxonomy: available through www.itis.govITIS logo

Identification: The genus Myleus needs systematic review. See Géry (1977) for key, synonymy, and color photographs. According to Géry, Myleus rubripinnis represents a complex and seems to be composed of several different forms that are difficult to distinguish. Photographs of Myleus species appeared in Axelrod et al. (1985) and Sakurai et al. (1993).
Size: 15 cm SL.
Native Range: Tropical America. This species complex is widely distributed in lowland areas of South America east of the Andes, including the Amazon, Orinoco, and Parana (Paraguay River) basins and various coastal drainages of the Guianas (Géry 1977).
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 Myloplus rubripinnis are found here.

StateFirst ObservedLast ObservedTotal HUCs with observations†HUCs with observations†
MA199119911Narragansett

Table last updated 3/28/2025

† Populations may not be currently present.
Means of Introduction: The fish was probably an aquarium release.
Status: Reported in Massachusetts.
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: According to the report the Massachusetts specimen was examined and identified as Myleus rubripinnis by Massachusetts Division of Fish and Wildlife biologist Richard Hartley, but was not retained (Hartel 1992). R. Hartley (personal communication) has recently indicated to us that identification of the fish as M. rubripinnis should be considered tentative at best. He used an aquarium book to identify the specimen but only had in his possession the specimen's head (the angler and his family had eaten the body) and a sketch prepared by the angler showing a fish with a long, hooked anal fin. In fact, because of taxonomic problems associated with chorused fishes, there remains some doubt that the Massachusetts fish was correctly identified even to genus.
References: (click for full references)

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.

Cardoza, J. E., G. S. Jones, T.W. French, and D. B. Halliwell. 1993. Exotic and translocated vertebrates of Massachusetts, 2nd edition. Fauna of Massachusetts Series 6. Massachusetts Division of Fisheries and Wildlife, Publication 17223-110-200-11/93-C.R, Westborough, MA.

Géry, J. 1977. Characoids of the world. Tropical Fish Hobbyist Publications, Inc., Neptune City, NJ.

Hartel, K. E. 1992. Non-native fishes known from Massachusetts freshwaters. Occasional Reports of the Museum of Comparative Zoology, Harvard University, Fish Department, Cambridge, MA. 2. September. pp. 1-9.

Hartley, R. - Massachusetts Department of Fish and Wildlife, Westborough, MA.

FishBase Summary
Author: Nico, L.
Revision Date: 5/30/2004
Peer Review Date: 5/30/2004

Citation Information:
Nico, L., 2025, Myloplus rubripinnis (Müller and Troschel, 1844): U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, https://nas.er.usgs.gov/queries/FactSheet.aspx?speciesID=425, Revision Date: 5/30/2004, Peer Review Date: 5/30/2004, Access Date: 3/28/2025

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.

Disclaimer:

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. [2025]. Nonindigenous Aquatic Species Database. Gainesville, Florida. Accessed [3/28/2025].

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Disclaimer:

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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