Analysis of variability in vertebral morphology and growth ring counts in two Carcharhinid sharks
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Inter- and intra-regional variations in vertebrae morphology and growth increment counts (band counts) were analyzed for two carcharhinid shark species, Carcharhinus plumbeus (n = 10) and C. limbatus (n = 11). Five sequential vertebrae were removed from the cervical region, above the branchial chamber and posterior to the chondrocrainium, and thoracic region, below the first dorsal fin. Dorsal–ventral height, medial–lateral breadth, and caudal–cranial length were measured for each sampled vertebra. Results indicate no significant difference in vertebral morphology within a sampled region of the vertebral column. However, a significant difference in vertebral morphology was noted between regions for both shark species, with thoracic vertebrae consistently larger than cervical vertebrae. A sub-set of three vertebrae was taken from each sampled region of each shark for sectioning and counting of growth increments. Analyses of growth increment counts by two readers indicated no significant difference in band counts within and between sampled regions.
KeywordsShark Growth Vertebrae Age Carcharhinus plumbeus Carcharhinuslimbatus
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The authors thank Alexia Morgan, Taylor Chapple, and Peter Cooper for assistance in collecting shark specimens for this study. We also thank Mike Allen for statistical guidance. Funding for this project came from the National Marine Fisheries Service’s Highly Migratory Species Division through the Florida Program for Shark research involvement in the National Shark Research Consortium.
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