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Abstract

Shark viewing tourism is a burgeoning global industry. Numerous operations provision sharks to increase sightings yet the effects of provisioning on shark behaviour are often poorly understood. At a unique provisioning site in Oslob, Cebu, Philippines, whale sharks () have become the focus of a mass tourism operation since late 2011, receiving over 185,000 tourists a year. To better understand and advise management bodies on the effects of provisioning on these animals, we used photographic identification (photo-ID) to assess the daily abundance and site visitation patterns of the sharks. Principal coordinate analysis (PCoA) based on co-occurrence matrices was used to investigate visitation patterns amongst individuals and define groupings. Modified maximum likelihood methods were then used to model mean residency for these different groups. Between March 31st 2012 and March 31st 2015, we identified 209 (165 males, 34 females and 10 of unknown sex) individuals at the site (a 0.065 km2 demarked area located 50 – 100 m from shore), with an average of 12.4 (SD = ± 4.8, range = 2 – 31) sharks sighted per day. Daily shark abundance increased over time and showed strong seasonal variation, with annual peaks occurring between May and November. We documented a spectrum of site visitation patterns ranging from single sighting (21% of sharks identified) to year-round residency (5% of sharks identified). For frequently sighted sharks, PCoA revealed two primary residency groupings: highly resident sharks ( = 9), which were seen year-round with few prolonged absences, and seasonal sharks ( = 21), which were primarily present between May and November. The daily abundance of highly resident sharks varied nonlinearly over time with no clear trend, while the daily abundance of seasonal sharks showed a clear increase during peak season in each year of the study. Mean residency for highly resident sharks was estimated at 55.5 ± 175.5 SE (95% CI 49.5 – 730.0) days, 58.3 ± 161.7 SE (95% CI 23.2 – 81.4) days for seasonal individuals, and 16.8 ± 1.8 SE (95% CI 14.8 – 22.2) days for infrequent sharks ( = 130). The difference in residency patterns between frequently sighted and infrequent individuals was almost fourfold. This shift in residency could have long-term implications for ca. 15% of identified whale sharks at the site. We provide insight into the impacts of provisioning on shark movements and inform the debate surrounding the future of this controversial activity.

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/content/papers/10.5339/qproc.2016.iwsc4.5
2016-05-15
2019-08-23
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