Date of Award

Spring 5-1-2023

Document Type

Thesis

Degree Name

Master of Science in Coastal Marine and Wetland Studies

Department

Coastal and Marine Systems Science

College

College of Science

First Advisor

Dan Abel

Second Advisor

Craig O'Connell

Third Advisor

Derek P. Crane

Additional Advisors

Ryan Rezek

Abstract

As bycatch continues to impact global shark populations, there is a continuing need for effective bycatch reduction devices. Prior research has shown promise in exploiting sharks' electrosensory ability to this end. We tested the deterrent efficacy of the Select Magnetic and Repellant Treated (SMARTTM) and the newly developed "SMARTER" hooks in experimental longline and hook-and-line trials. Both are magnetized and contain an electropositive metal component made of magnesium (SMART) and a magnesium alloy designed to extend longevity (SMARTER). We deployed 127 longlines with SMART hooks, SMARTER hooks, controls, and procedural controls from 2021-2022 in Winyah Bay, South Carolina, and caught 134 sharks composed of 7 species (Carcharhinus isodon, Carcharhinus leucas, Carcharhinus limbatus, Carcharhinus plumbeus, Negaprion brevirostris, Rhizoprionodon terraenovae, Sphyrna tiburo). Additionally, hook-and-line trials testing the SMART hook alongside controls were conducted over 73 days from 2021-2022 at Myrtle Beach (South Carolina) State Park and caught 117 sharks composed of 5 species (Carcharhinus acronotus, C. plumbeus, Mustelus canis, R. terraenovae, Sphyrna lewini). Catch-per-unit-effort did not significantly differ among SMART, SMARTER, and control hooks in longline or hook-and-line trials. Further testing of SMART and SMARTER hooks with other species and increased strength of the hooks' electromagnetic fields is needed to determine if electropositive hooks are a viable option for reducing shark bycatch.

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