Scarring patterns of whale sharks at a provisioning site in the Philippines

Scarring patterns of whale sharks, Rhincodon typus, at a provisioning site in the Philippines

Luke Penketh, Anna Schleimer, Jessica Labaja, Sally Snow, Alessandro Ponzo, Gonzalo Araujo

ABSTRACT:

1. Shark‐based tourism continues to be a rapidly growing industry, and thus understanding the impacts of such activities is essential to mitigate the potential negative effects on the target species. The consequences of provisioning on whale sharks (Rhincodon typus) are not fully understood, although changes to the local environment, ecology, behaviour, and site visitation patterns have been highlighted. Here, the scarring patterns of whale sharks were investigated at a provisioning site in Oslob, Cebu, Philippines, as an indicator of the physical impacts of tourism activities on individual sharks. Photographic identification was used to attribute scars to individual animals (n = 152) between March 31, 2012 and January 31, 2015.

2. Scars were categorized by type and body location, and were compared with non‐provisioned aggregations in Australia, Mozambique, and Seychelles. Oslob whale sharks were more scarred than other studied populations, with 94.7% (n = 144) having at least one scar, and with 90.8% (n = 138) having more than one scar. Scarring incidence was found to be significantly higher in sharks that regularly visited the provisioning site, and analysis of scarring over time in highly resident sharks showed that all individuals gained scars through periods of consistent re‐sightings. A significantly higher incidence of minor scar types was found, most commonly on the dorsal side of the animal, probably resulting from sustained proximity to boats and ropes throughout the provisioning activities. The consequences of interactions with propeller boats were observed, despite a ban on their use in the provisioning site, highlighting the risk to the species beyond the study site.

3. We recommend the strict enforcement of a minimum distance between boats and sharks, a zero‐contact policy during interactions, the expansion of the provisioning site, and the implementation of a no‐boat‐access zone around the perimeter of the provisioning site to mitigate potential collisions.

Aquatic Conservation, Early View, DOI: 10.1002/aqc.3437

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