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Abstract

Whale shark tourism is increasingly popular at coastal predictable aggregations around the world. However, only one description accounts for provisioning of whale sharks (), which is at Oslob, Philippines, where sharks are provisioned between 6 am and 1 pm daily within a demarked tourist interaction area. Understanding the potential effects of provisioning on the behaviour of this species is important for their conservation. To investigate whether whale shark diving behaviour was affected by the provisioning, four whale sharks with known extended residency at the study site were tagged with CEFAS G5 temperature-depth-recorder (TDR) tags. Three individuals were juvenile males with estimated total lengths of 4.5, 5.0 and 6.5 m (P-432, P-480 and P-403 respectively), and a fourth individual was a juvenile female measuring 5.5 m (P-385). A Hawaiian-sling spear pole was used to deliver stainless steel anchors with a tether carrying a swivel 10 cm into the subdermal layer of the whale sharks on the ventral side between the first dorsal fin and the first lateral ridge. Three TDR tags were randomly deployed amongst the individuals over a period of 18 months. Linear mixed effect models were used to test how attendance at the provisioning site affected shark depth use and variability. Tags were deployed for an average duration of 49.5 provisioned days (sharks present daily at the site) and 33.8 non-provisioned days (sharks were absent from the site). The deepest dive was recorded by P-403 to 1,251 m, at a minimum temperature of 12.1 °C. The tags revealed a pronounced shift in habitat use by individuals when away from the provisioning site. Specifically, during provisioned days, time spent at the surface (0 – 2 m) between 6 am and 1 pm was . six times longer than during non-provisioned days. During provisioned days, deep dives occurred mostly near or at the end of the provisioning activities (i.e. 10 am to 2 pm), whereas on non-provisioned days, deep dives occurred mostly between 4 am and 10 am. This shift could suggest that whale sharks have a need to thermoregulate following a prolonged period of time at the surface where temperatures regularly exceed 31 °C. The use of TDR tags on whale sharks revealed modified diving behaviour at Oslob, a unique provisioning site. This behavioural modification should be considered when developing guidelines for sustainable tourism and conservation measures for the species.

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/content/papers/10.5339/qproc.2016.iwsc4.4
2016-05-15
2019-09-19
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http://instance.metastore.ingenta.com/content/papers/10.5339/qproc.2016.iwsc4.4
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