Testing of Electrical and Magnetic Stimuli on Captive Juvenile Tiger Sharks

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dc.contributor.advisorHolland, Kim N.
dc.contributor.authorCardona, Edward William
dc.contributor.departmentMarine Biology
dc.date.accessioned2024-10-09T23:45:27Z
dc.date.issued2024
dc.description.degreeM.S.
dc.embargo.liftdate2026-10-08
dc.identifier.urihttps://hdl.handle.net/10125/108639
dc.subjectBehavioral sciences
dc.subjectDeterrent
dc.subjectElectric
dc.subjectFisheries
dc.subjectMagnetic
dc.subjectSharks
dc.titleTesting of Electrical and Magnetic Stimuli on Captive Juvenile Tiger Sharks
dc.typeThesis
dcterms.abstractTiger sharks (Galeocerdo cuvier) are both ecologically and culturally important in Hawaii. It is also one of the species most frequently involved in attacks on humans worldwide Deterring sharks from biting unintended items has importance in three spheres – human safety, reducing shark bycatch in fisheries and reducing depredation (sharks biting target species that have already been hooked). Because sharks can sense electromagnetic fields, artificial electrical and magnetic stimuli have been hypothesized as solutions to mitigate these interactions. Previous research has focused on testing a variety of putative deterrent devices in captivity but often suffers from low sample sizes or small test arenas. Results from experiments in the wild can be confounded by uncontrolled variables (e.g., level of hunger). To address these concerns, I tested captive juvenile tiger sharks in a large naturalistic enclosure where hunger could be controlled. This study is the first to test putative deterrents (two permanent magnets - weak and strong fields - and an electric field transmitter) on tiger sharks in a controlled experimental protocol. I hypothesized that the fields produced by these devices would be aversive to sharks, and stronger magnets would be more effective than weaker ones. Eleven captive juvenile tiger sharks were exposed to the three devices under both baited (food) and unbaited conditions. Results showed uneven responses to all three devices depending on whether bait was present. In some circumstances deterrence was observed but the tests also revealed attractive properties of artificial magnetic fields. All responses occurred <1 meter from the deterrent device. The strong magnet and the electrical transmitter were found to reduce the probability of sharks taking the bait. However, the weaker permanent magnet showed signs of being attractive. These stimuli were not 100% effective under all conditions and, as in previous studies, there was individual variability in responsiveness among sharks. These findings highlight the importance of context dependent and species-specific testing of putative magnetic and electric deterrents.
dcterms.extent72 pages
dcterms.languageen
dcterms.publisherUniversity of Hawai'i at Manoa
dcterms.rightsAll UHM dissertations and theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission from the copyright owner.
dcterms.typeText
local.identifier.alturihttp://dissertations.umi.com/hawii:12320

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