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Heeding the History of Kahu Manō: Developing and Validating a Pono Photo-Identification Methodology for Tiger Sharks (Galeocerdo cuvier) in Hawaiʻi

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Title:Heeding the History of Kahu Manō: Developing and Validating a Pono Photo-Identification Methodology for Tiger Sharks (Galeocerdo cuvier) in Hawaiʻi
Authors:Nakachi, Kaikea
Contributors:Grabowski, Tim (advisor)
Tropical Conservation Biology & Environmental Science (department)
Keywords:Conservation biology
Natural resource management
Hawaiʻi
Photo-Identification
Shark
Date Issued:Dec 2021
Publisher:University of Hawaii at Hilo
Abstract:Amidst concurrent global declines in shark populations and advancements in camera technology, underwater photo-identification (photo-ID) is increasingly being used to unobtrusively gather data on potentially sensitive species. Tiger sharks (Galeocerdo cuvier) are prime photo-ID candidates, particularly in places where population data is scarce and they hold a significant role in customary practices and beliefs, such as Hawaiʻi. This study emulates traditional Hawaiian practices of kahu manō, i.e., shark keepers, through implementation of non-intrusive contemporary approaches to develop, assess, and validate photo-ID methodology as a pono, or respectfully appropriate, technique for tiger shark research in Hawaiʻi. An identification system reliant on chronologically subdividing the dataset based on sex and caudal fin condition and then using 14 identifiable traits to match unknown tiger sharks to a database of previously sighted individuals was developed. This identification system complements Native Hawaiian approaches of observation and anaylsis, such as kilo and the papakū makawalu process developed by the Edith Kanakaʻole Foundation. Volunteers with varying experience with tiger sharks and photo-ID, were trained to use this identification system and exhibited > 90% agreement in tiger shark ID with each other and the method developer. The time taken by an observer to identify an individual negatively influenced the probability of agreement with other observers, including the expert observer. In contrast, observer-reported certainty positively influenced the probability of agreement. This validated method was used to ID individual tiger sharks (n=69) in West Hawaiʻi during 2005-2021, including the observation of 1 male shark and 1 female shark across 16 years. This study identifies important parameters of photo-ID that can aid future photo-ID experimental design and demonstrates the capacity for safe and respectful research methods that parallel Native Hawaiian cultural practices. The validation of underwater photo-ID methodology contributes an important non-invasive approach to research and inform management in Hawaiʻi, and its continued implementation and accompanying analyses as pono scientific techniques have the potential to obtain meaningful life-history information on an important ecological and cultural species.
Pages/Duration:64 pages
URI:http://hdl.handle.net/10790/6865
Rights:All UHH 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.
Appears in Collections: TCBES Theses
Tropical Conservation Biology and Environmental Science


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