Grace Casselberry Awarded Prestigious Fellowship from AAUW to Study Sharks and Sea Turtles
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Dr. Grace Casselberry, postdoctoral research associate in the College of Natural Sciences’s Department of Environmental Conservation (ECo), was recently awarded the American Postdoctoral Research Leave Fellowship from the American Association of University Women (AAUW). The proposed research submitted for this fellowship will assess the predator-prey dynamics of tiger sharks (Galeocerdo cuvier) and four sea turtle species in St. Croix, U.S. Virgin Islands (USVI).
“I am honored to have been selected for this award from the AAUW to support me, as a postdoc, as well as my research,” said Casselberry. “The award is open to women across all disciplines of research, and having them see the value of my work across such a wide applicant pool is really special. It is exciting to get to continue to build my career here in the ECo department, where I also did my graduate research.”
Relationships among predators and prey play a significant role in structuring biotic communities and individual populations. “Predators can have a strong influence on prey across landscapes, influencing distribution, abundance, and daily behavioral decisions,” explained Casselberry. “The reverse is also true: aggregations of prey, particularly for reproductive purposes, can influence predator migratory patterns. Our understanding of these connections is quite limited in marine environments, especially for marine megafauna, like large sharks and sea turtles, which are highly migratory. These species are also often experiencing population declines from human activities, making it even more important to understand these relationships.”
Shark populations are largely depleted in the Caribbean, and spatial ecology studies on sharks in the USVI are limited. Since 2019, Casselberry has tracked tiger sharks in St. Croix, using two electronic tagging technologies to characterize their broad migratory patterns and fine-scale movements within Buck Island Reef National Monument, a marine-protected area. St. Croix is also home to nesting beaches used by leatherback (Dermochelys coriacea), green (Chelonia mydas), hawksbill (Eretmochelys imbricata), and loggerhead (Caretta caretta) sea turtles, which have been monitored for more than three decades by the National Park Service, U.S. Fish and Wildlife Service, U.S. Geological Survey, and the St. Croix Sea Turtle Project, a non-profit initiative with the Ocean Foundation.
“In recent years, biologists have documented an increase in shark-related injuries and fewer nesting events, particularly for leatherbacks at Sandy Point, which may correspond to a stabilization in the U.S. tiger shark population,” said Casselberry. To better understand the role sharks may play in these changes, Casselberry plans to characterize the predator-prey dynamics between tiger sharks and the aforementioned sea turtle species across spatial scales by integrating telemetry and standardized nesting survey data. This will improve scientists’ understanding of predator-prey dynamics and help inform future management decisions for continued successful sea turtle conservation at the local and federal level in the face of continued shark conservation success.
“On land and in the ocean, our apex predators have historically been depleted,” argued Casselberry. “It has taken decades of work to help these populations begin to show signs of recovery, but that recovery can lead to new complications for conservation when the predators eat endangered prey. This study will help us begin to understand these interconnections in marine systems.”