The effect of environmental factors on movement patterns and habitat use of young-of-the-year scalloped hammerhead sharks (Sphyrna lewini) in the Tolomato River nursery

Author

Matthew BernankeFollow

Year

2023

Season

Fall

Paper Type

Master's Thesis

College

College of Arts and Sciences

Degree Name

Master of Science in Biology (MS)

Department

Biology

NACO controlled Corporate Body

University of North Florida. Department of Biology

First Advisor

Dr. Jim Gelsleichter

Second Advisor

Dr. Kelly Smith

Third Advisor

Dr. Bryan Franks

Abstract

Various shark populations on the southeastern coast of the United States experienced declines in the late 20^th century, including the scalloped hammerhead shark (Sphyrna lewini). Improved management strategies, implemented in the late 1990s, have helped these populations to recover, but they are still under threat from fishing pressure and habitat loss. In continuing to strive towards population recovery and conservation, it is important to identify Essential Fish Habitat, or habitats that are necessary for the spawning, feeding, breeding, or growth of marine organisms. One such habitat is that of the shark nursery habitat. Nursery habitats are those which are defined by three major criteria. First, sharks are more commonly encountered here than in other areas. Next, sharks have a habit or remining in or returning to the area. Lastly, the area is repeatedly used across years. Recently, Wargat (2021) determined that a section of the Tolomato River, a part of the Intracoastal Waterway in northeast Florida, serves as a nursery habitat for young-of-the-year (YOY) S. lewini. As discussed by Wargat, more data are needed regarding spatial use within the nursery as well as the abiotic and biotic factors that influence this use. To address these gaps in knowledge, active and passive acoustic telemetry analyses were conducted for YOY S. lewini in the Tolomato River. Results from these studies indicate that Pine Island Sound serves as the center of the nursery and the selection of this microhabitat by YOY S. lewini does not seem to be influenced by water quality factors. The identification of this microhabitat preference, as well as the seeming lack of abiotic influence on movement patterns and habitat use, aids in expanding our understanding of how YOY S. lewini utilize a newly defined nursery. In turn, this can aid us in conserving a predictable population of a recovering species that is critically endangered globally.

Suggested Citation

Bernanke, Matthew, "The effect of environmental factors on movement patterns and habitat use of young-of-the-year scalloped hammerhead sharks (Sphyrna lewini) in the Tolomato River nursery" (2023). UNF Graduate Theses and Dissertations. 1239.
https://digitalcommons.unf.edu/etd/1239