Age, Growth and Reproduction of Western North Atlantic Butterfly Rays (Myliobatiformes: Gymnuridae), with the Description of Two New Species
Batoid fishes are among the most threatened and least understood chondrichthyan species worldwide due to their large body size, conservative life-history characteristics, and predominantly coastal distributions where fishing and habitat degradation threaten the stability of populations. A lack of em...
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| Format: | Text |
| Language: | English |
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W&M ScholarWorks
2017
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| Online Access: | https://scholarworks.wm.edu/etd/1516639565 https://doi.org/10.21220/V58T7S https://scholarworks.wm.edu/context/etd/article/1192/viewcontent/Parsons_vims_0261D_10023.pdf |
| Summary: | Batoid fishes are among the most threatened and least understood chondrichthyan species worldwide due to their large body size, conservative life-history characteristics, and predominantly coastal distributions where fishing and habitat degradation threaten the stability of populations. A lack of empirical life history data is widespread across batoid taxa — nearly half of all species are considered data deficient, thus hindering species assessments and the development of effective management strategies. Furthermore, many batoid taxa are in need of taxonomic re-examination. Increasing our understanding of life history traits that determine population productivity, such as age and size at maturity, growth rate, and fecundity is prerequisite to examining the potential for populations to increase or stabilize in response to fishing mortality. The Butterfly Rays (Myliobatiformes: Gymnuridae) are comprised of 10 globally distributed species that inhabit shallow coastal regions and are commonly caught in benthic fishing gears targeting commercially valuable species. Two species are recognized in the western Atlantic: the Spiny Butterfly ray, Gymnura altavela (Linnaeus 1758), and the Smooth Butterfly Ray, G. micrura (Bloch & Schneider 1801). Previous life history studies on U.S. Butterfly Rays were often spatially and temporally limited, which may bias conclusions due to underrepresentation of some life stages, and lead to inaccurate biological characterizations. Furthermore, sexual dimorphism and ontogenetic variability in body shape, and inter- and intraspecific inconsistencies in taxonomic characters (e.g., disk coloration, tail banding patterns) have contributed to substantial taxonomic confusion in the Gymnuridae. To address knowledge gaps in the life history and taxonomy of western Atlantic Butterfly Rays, this dissertation describes the age and growth of G. altavela, the reproductive biology of G. altavela and G. micrura, and the taxonomic status of G. micrura. The largest male and female G. altavela were ... |
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