Nearshore marine environments are known to be highly productive systems with relatively high faunal diversity and abundances, but these systems are particularly vulnerable to negative impacts from anthropogenic disturbances that can result in habitat degradation. Despite these challenges, many shark species of various life stages utilize coastal shelf habitats, inshore estuaries, and bays. The inshore habitats of Cumberland and Nassau Sounds in northeast Florida have been proposed as potential nursery grounds by earlier work, but this suggestion did not satisfy all of the standard criteria of shark nursery designation. It has recently been stated that the combination of surveys inside and outside suspected nursery habitats, especially those incorporating mark-recapture studies, would provide a very comprehensive test of the nursery criteria. A primary objective of the present study was to initially describe the composition and abundance of shark populations utilizing the nearshore habitats of northeast Florida, while also comparing them to inshore communities, with emphasis on spatial and temporal variations in assemblages. Fishery-independent longline sampling was conducted across the region and while considerable overlap of species were observed, significant differences in community structure between inshore and nearshore locations were detected. Specifically, the inshore waters of the First Coast support nursery habitat designation for Atlantic sharpnose, blacktip, and sandbar sharks after satisfying the accepted criteria. Given the high amounts of spatial and temporal overlap observed along the First Coast, relative trophic niche dynamics were also investigated via stable isotope analysis of two tissue types. These results revealed varying trophic niche sizes in the long term, but suggest some degree of shared resource use when animals are present on the First Coast. The identification of factors that influence coastal shark habitat utilization, such as competition and resource use, can contribute to understanding and predicting how they may respond to future environmental changes.
| Identifer | oai:union.ndltd.org:unf.edu/oai:digitalcommons.unf.edu:etd-1907 |
| Date | 01 January 2018 |
| Creators | Morgan, Clark R |
| Publisher | UNF Digital Commons |
| Source Sets | University of North Florida |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | UNF Graduate Theses and Dissertations |
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