The need for long-term population monitoring of the world’s largest fish
KAUST DepartmentDivision of Biological and Environmental Science and Engineering, Red Sea Research Center, King Abdullah University of Science and Technology, Thuwal 23599-6900, Saudi Arabia
Reef Ecology Lab
Marine Science Program
Red Sea Research Center (RSRC)
Biological and Environmental Science and Engineering (BESE) Division
Environmental Science and Engineering Program
Permanent link to this recordhttp://hdl.handle.net/10754/676350
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AbstractABSTRACT: Many large marine species are vulnerable to anthropogenic pressures, and substantial declines have been documented across a range of taxa. Many of these species are also long-lived, have low individual resighting rates and high levels of individual heterogeneity in capture probability, which complicates assessments of their conservation status with capture-mark-recapture (CMR) models. Few studies have been able to apply CMR models to whale sharks Rhincodon typus, the world’s largest fish. One of their aggregation sites off Mafia Island in Tanzania is characterised by unusually high residency of this Endangered species, making it an ideal target for CMR methods. Three different CMR models were fitted to an 8 yr photo-identification data set to estimate abundance, population trend and demographic parameters. As anticipated, resighting rates were unusually high compared to other aggregations. Different CMR models produced broadly similar parameter estimates, showing a stable population trend with high survivorship and limited recruitment. Tagging and biopsy sampling for concurrent research did not negatively affect those sharks’ apparent survival or capture probabilities. Scenario-based power analyses showed that only pronounced abundance trends (±30%) would be detectable over our study period, at a 90% level of probability, even with the relatively high precision in yearly abundance estimates achieved here. Other, more transient whale shark aggregations, with reduced precision in abundance estimates, may only be able to confidently detect a similar trend with CMR models after 15-20 yr of observations. Precautionary management and long-term monitoring will be required to assist and document the recovery of this iconic species.
CitationRohner, C., Venables, S., Cochran, J., Prebble, C., Kuguru, B., Berumen, M., & Pierce, S. (2022). The need for long-term population monitoring of the world’s largest fish. Endangered Species Research, 47, 231–248. https://doi.org/10.3354/esr01177
SponsorsFunded by AquaFirma, the Shark Foundation, WWF Tanzania, WWF Sweden/SIDA, Waterlust, 2 private trusts, and Patreon supporters. We thank Liberatus Mokoki and his team for their assistance in the field, and Jason Rubens, Mathias Igulu, Haji Machano, Paul Kugopya, Sware Semesi, the WWF Tanzania team as well as Amin Abdallah from the Mafia Island Marine Park for facilitating the project. Thanks to Carlos Omari and the team at Whale Shark Lodge and to Jean and Anne de Villiers for hosting us. Thanks to Fernando Cagua for his help in the field and his feedback on the manuscript. We thank Kenny Wolfe, Jens Paulsen, Rilke Ballero, Alexandra Watts, Stella Diamant, Sophia Lind, Lydie Couturier and David Robinson for their help in the field and Alina Riensema and Michael Pfundt for help with photo-ID processing. We thank all citizen scientists who contributed photo-ID data, particularly the team from Kitu Kiblu. Thanks also to the MMF team and board for administrative support.
PublisherInter-Research Science Center
JournalEndangered Species Research
Except where otherwise noted, this item's license is described as Archived with thanks to Endangered Species Research under a Creative Commons license, details at: https://creativecommons.org/licenses/by/4.0/