Marcus Drymon results 28
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Evidence of a potential sandbar shark (Carcharhinus plumbeus) nursery in the Western Gulf of MexicoOA Marine
Introduction Nursery areas for sandbar sharks ( Carcharhinus plumbeus ) are well-delineated along the Atlantic coast of the United States, with only a single nursery area identified in the Gulf of Mexico on the west coast of Florida. Methods Fishery-independent surveys and fishery-dependent data were used to explore the frequency and seasonality of young-of-the-year (YOY) sandbar sharks off the coast of Texas. Results Data pre...
Aim Some habitats serve particularly important functions for wildlife. Identifying and appropriately managing these ‘essential habitats’ is critical, especially for wildlife that have faced severe population declines like sharks. Nursery habitats aid in the survival and development of juvenile sharks, which until recently were not formally identified or managed throughout most regions. Managing shark nurseries was in part chal...
Marine megafauna species are affected by a wide range of anthropogenic threats. To evaluate the risk of such threats, species’ vulnerability to each threat must first be determined. We build on the existing threats classification scheme and ranking system of the International Union for Conservation of Nature (IUCN) Red List of Threatened Species by assessing the vulnerability of 256 marine megafauna species to 23 at‐sea threat...
Determining the distributions of marine animals is a challenge, particularly for highly migratory species like sharks. In the United States, several shark populations are beginning to recover following exploitation, including the white shark ( Carcharodon carcharias ). Recently, reports of white sharks have increased in the northern Gulf of Mexico (hereafter Gulf), but determining whether these reports represent actual changes...
Depredation: An old conflict with the seaNARA Subscribed
Depredation (the partial or complete removal of a hooked species by a non‐target species) is a human–wildlife conflict as old as humans and the sea. In some ways, depredation is no different today than it was a century ago. But in many ways, this conflict has become more complicated. Following three decades of successful management, some US shark populations have begun to rebuild. However, many anglers attribute perceived incr...
Aim Biogeographic boundaries and genetic structuring have important effects on the inferences and interpretation of effective population size ( N e ) temporal variations, a key genetics parameter. We reconstructed the historical demography and divergence history of a vulnerable coastal high‐trophic shark using population genomics and assessed our ability to detect recent bottleneck events. Location Western and Central Indo‐Pac...
A better understanding of trophic interactions between hardhead catfish (Ariopsis felis) and gafftopsail catfish (Bagre marinus) is crucial for developing multi-species management strategies for the northern Gulf of Mexico (GOM). These two species are often aggregated in food web models; however, limited data are available to substantiate this approach. Therefore, the present study aimed to describe the dietary habits of hardh...
Philopatry influences the genetic population structure of the blacktip shark ( Carcharhinus limbatus ) at multiple spatial scalesNARA Subscribed
Understanding how interactions among microevolutionary forces generate genetic population structure of exploited species is vital to the implementation of management policies that facilitate persistence. Philopatry displayed by many coastal shark species can impact gene flow and facilitate selection, and has direct implications for the spatial scales of management. Here, genetic structure of the blacktip shark ( Carcharhinus l...
The goals of this study were to generate baseline population dynamics parameters for Gulf of Mexico crevalle jack Caranx hippos and examine the foraging habits of Mississippi and Alabama crevalle jack. Specimens were collected from Mississippi, Alabama and Florida, and age was estimated from sagittal otoliths. Stomachs from some specimens were retained for dietary analyses. Age classes spanned 0–20 years. Overall growth was be...
Understanding dispersal in large marine fauna is necessary for conservation, but movement patterns often vary widely by sex and life stage. In sharks, genetic studies have shown evidence of widespread male-biased dispersal, though tagging and tracking studies on the same populations show both sexes using site fidelity, including philopatry, and moving similar distances. We used a suite of microsatellite loci and DNA samples fr...
Understanding habitat use of elasmobranchs in pelagic environments is complicated due to the mobility of these large animals and their ability to move great distances in a three-dimensional environment. The Gulf of Mexico is a region where many highly migratory pelagic shark species occur, while in close proximity to coastal, anthropogenic activity including recreational and commercial fisheries. This study provides summary in...
Two different methods, metagenetics and free‐otolith identification, were used to identify prey in the stomach contents of 531 Gymnura lessae captured by trawling in Mobile Bay, Alabama 2016–2018. Both methods were found to produce analogous results and were therefore combined into a single complete dataset. All prey were teleosts; the families Sciaenidae and Engraulidae were the most important prey (prey specie index of relat...