Distinguishing Black Bullhead (Ameiurus melas) from Brown Bullhead (A. nebulosus) can be difficult, in part, due to conflicting evidence regarding reliable meristic and morphological characters with which to base identifications. The possibility of hybrids with intermediate traits further complicates diagnosis. Identification guides have typically focused on adults, leaving guidance for juveniles largely undescribed. We compared morphological identifications of Black Bullhead and Brown Bullhead with a cytochrome c oxidase I (COI) barcode and microsatellite assignments. Specifically, we examined: (1) gill-raker count, (2) anal-fin ray count, (3) prominence of pectoral-spine serrae, (4) DNA barcoding using the COI gene, and (5) cluster analysis of nine microsatellite loci. With the exception of anal-fin ray counts, we found a high degree of agreement among all methods. Microsatellite analysis identified two clearly distinct genetic groups, and these groups corresponded to individuals identified as Black Bullhead and Brown Bullhead based on morphology. Although Black Bullhead and Brown Bullhead did not share COI haplotypes (except for one individual), we found greater intraspecific genetic distances among individuals identified as Brown Bullhead than between Brown Bullhead and Black Bullhead, demonstrating that caution is warranted against using COI haplotypes as a barcode to solely distinguish the two species. Pectoral-spine serrae prominence was a useful character to distinguish the two species and worked especially well on individuals <125 mm total length. Gill-raker counts of euthanized fish in the laboratory were appropriate for the identification of all sizes of Black Bullhead and Brown Bullhead (using the lowest number of gill rakers on the first gill arch if asymmetry was observed). Finally, microsatellites did not show evidence of recent hybridization at our sampling sites. We recommend using pectoral-spine serrae prominence to distinguish between Black Bullhead and Brown Bullhead in the field and using gill-raker counts for laboratory based identification.
|Original language||English (US)|
|Number of pages||15|
|Journal||American Midland Naturalist|
|State||Published - Jan 21 2020|
Bibliographical noteFunding Information:
Acknowledgments.—We acknowledge the many field staff of the University of Minnesota Duluth Natural Resources Research Institute for collecting fish under the authority of Wisconsin Scientific Collector Permits SCP-NER-126 and SCP-NOR-332-0512, and a Michigan Scientific Collector Permit with final amendments approved 5/30/2012. Fish handling and euthanasia procedures were approved in protocol 1103A96832 from the Institute for Animal Care and Use Committee at University of Minnesota Duluth. We thank Drs. D. Uzarski, V. Brady, and M. Cooper for overall project management. Dr. J. Gathman engaged in valuable discussions on bullhead identification that improved the content of this manuscript. Funding for this work was provided by the Great Lakes National Program Office under the United States Environmental Protection Agency, grant number GL-00E00612-0 as part of the US federal government’s Great Lakes Restoration Initiative. Although the research described in this work has been partly funded by the United States Environmental Protection Agency, it has not been subjected to the agency’s required peer and policy review and therefore does not necessarily reflect the views of the agency and no official endorsement should be inferred. This paper is contribution number 632 of the Natural Resources Research Institute, University of Minnesota Duluth.
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