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Validity, Identification, and Distribution of the Roundscale Spearfish, Tetrapturus georgii (Teleostei: Istiophoridae): Morphological and Molecular Evidence
Bulletin of Marine Science
  • Mahmood S. Shivji, Nova Southeastern University
  • Jennifer E. Magnussen, Nova Southeastern University
  • Lawrence R. Beerkircher, Southeast Fisheries Science Center
  • George Hinteregger, Southeast Fisheries Science Center
  • Dennis W. Lee, Southeast Fisheries Science Center
  • Joseph E. Serafy, Southeast Fisheries Science Center
  • Eric D. Prince, Southeast Fisheries Science Center
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Peer Reviewed

The roundscale spearfish, Tetrapturus georgii Lowe, 1840, is known only from four specimens from the Mediterranean and eastern North Atlantic. Additional specimens have not been identified since 1961, making the validity and distribution of this species unclear. Analysis of 16 billfish specimens from the western North Atlantic on the basis of scale morphology, anus position, and mitochondrial DNA confirms the validity of this species and extends its distribution. Mid-lateral scales are soft, notably rounded anteriorly, and bear 2–3 points distinct from those of the sympatric longbill spearfish (Tetrapturus pfluegeri Robins and de Sylva, 1963) and white marlin (Tetrapturus albidus Poey, 1860). Position of anus relative to first anal fin and a related morphometric ratio (distance from anus to first anal fin origin: height of first anal fin) are intermediate between T. pfluegeri and T. albidus. These characteristics match those described by Robins (1974) from the four eastern North Atlantic specimens of T. georgii. The mitochondrial ND4L, ND4, and cyt b gene sequences strongly support reciprocal monophyly of the western North Atlantic specimens relative to other Atlantic istiophorids. The difficulty in distinguishing between morphologically similar T. georgii and T. albidus in the field and the previously unrecognized presence of T. georgii in the western North Atlantic has implications for stock assessments of T. albidus, a species that is severely overfished.


©2006 Rosenstiel School of Marine and Atmospheric Science of the University of Miami

Additional Comments
This study was supported by funds from the National Marine Fisheries Service, the Guy Harvey Research Institute, AFTCO Inc., and a National Oceanic and Atmospheric Administration Dr. Nancy Foster Scholarship to J. Magnussen.
Citation Information
Mahmood S. Shivji, Jennifer E. Magnussen, Lawrence R. Beerkircher, George Hinteregger, et al.. "Validity, Identification, and Distribution of the Roundscale Spearfish, Tetrapturus georgii (Teleostei: Istiophoridae): Morphological and Molecular Evidence" Bulletin of Marine Science Vol. 79 Iss. 3 (2006) p. 483 - 491 ISSN: 0007-4977
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