Failure of phenotypic markers to accurately identify black bass species and associated hybrids in Mobile River Basin, Alabama

Authors: LEWIS, MATTHEW - Auburn University; SILLIMAN, KATHERINE - Auburn University; Beck, Benjamin; SAMMONS, STEVEN - Auburn University; PEATMAN, ERIC - Auburn University

Submitted to: North American Journal of Fisheries Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/19/2021
Publication Date: 7/20/2021
Citation: Lewis, M.R., Silliman, K.E., Beck, B.H., Sammons, S.M., Peatman, E.J. 2021. Failure of phenotypic markers to accurately identify black bass species and associated hybrids in Mobile River Basin, Alabama. North American Journal of Fisheries Management. 41(5):1591-1601. https://doi.org/10.1002/nafm.10673.
DOI: https://doi.org/10.1002/nafm.10673

Interpretive Summary: Hybridization among the black basses (Micropterus spp.) occurs due to reproductive barriers and manmade factors such as habitat alteration. Introduction of previously unintroduced species can also result in hybrid swarms and in some cases, elimination or reductions in native species. Hybridization is a major conservation concern for the black basses, which underscores the need for accurate identification of hybrids that often have unclear phenotypes (visible traits). To that end, we collected 1,723 fish from four river systems in the Mobile River Basin, Alabama, to compare phenotypic identification in the field based on morphology with genotype determined from single-nucleotide polymorphism (SNP) analysis using diagnostic markers for black basses. Results indicate that the visible (using the naked eye) identification among these cryptic hybrids is only 11% accurate. Only 4% of the fish collected were identified as hybrids in the field, whereas genotype analysis classified 22% of fish as hybrids. The majority of those misidentified in the field were hybrids between Alabama Bass (M. henshalli) and Redeye Bass (M. coosae) or those species along with another black bass species. Hybrid individuals composed 5-38% of the total number of fish collected from the four river systems, but 28-68% were misidentified in each river system. These results underscore the need for genetic tools to augment classic field surveys in the black basses as cryptic hybridization may lead to errant management decisions based on inaccurate species distribution assessments.

Technical Abstract: Hybridization among the black basses (Micropterus spp.) occurs due to weak postzygotic reproductive barriers and anthropogenic factors such as habitat alteration. Introduction of previously allopatric species can also result in hybrid swarms and in some cases, extirpation of native species. Introgressive hybridization is a major conservation concern for the more range-restricted black basses, which underscores the need for accurate identification of hybrids that often have cryptic phenotypes. To that end, we collected 1,723 fish from four river systems in the Mobile River Basin, Alabama, to compare phenotypic identification in the field based on morphology with genotype determined from single-nucleotide polymorphism (SNP) analysis using diagnostic markers for black basses. Results indicate that phenotypic identification among these cryptic hybrids is only 11% accurate. Only 4% of the fish collected were identified as hybrids in the field, whereas genotype analysis classified 22% of fish as hybrids. The majority of those misidentified in the field were hybrids between Alabama Bass (M. henshalli) and Redeye Bass (M. coosae) or those species along with another black bass species. Hybrid individuals composed 5-38% of the total number of fish collected from the four river systems, but 28-68% were misidentified in each river system. These results underscore the need for genetic tools to augment classic field surveys in the black basses as cryptic hybridization may lead to errant management decisions based on inaccurate species distribution assessments.