Opportunistic Visitors: Long-Term Behavioural Response of Bull Sharks to Food Provisioning in Fiji

Abstract

Shark-based tourism that uses bait to reliably attract certain species to specific sites so that divers can view them is a growing industry globally, but remains a controversial issue. We evaluate multi-year (2004–2011) underwater visual (n = 48 individuals) and acoustic tracking data (n = 82 transmitters; array of up to 16 receivers) of bull sharks Carcharhinus leucas from a long-term shark feeding site at the Shark Reef Marine Reserve and reefs along the Beqa Channel on the southern coast of Viti Levu, Fiji. Individual C. leucas showed varying degrees of site fidelity. Determined from acoustic tagging, the majority of C. leucas had site fidelity indexes >0.5 for the marine reserve (including the feeding site) and neighbouring reefs. However, during the time of the day (09:00–12:00) when feeding takes place, sharks mainly had site fidelity indexes <0.5 for the feeding site, regardless of feeding or non-feeding days. Site fidelity indexes determined by direct diver observation of sharks at the feeding site were lower compared to such values determined by acoustic tagging. The overall pattern for C. leucas is that, if present in the area, they are attracted to the feeding site regardless of whether feeding or non-feeding days, but they remain for longer periods of time (consecutive hours) on feeding days. The overall diel patterns in movement are for C. leucas to use the area around the feeding site in the morning before spreading out over Shark Reef throughout the day and dispersing over the entire array at night. Both focal observation and acoustic monitoring show that C. leucas intermittently leave the area for a few consecutive days throughout the year, and for longer time periods (weeks to months) at the end of the calendar year before returning to the feeding site.

Conservation challenges of sharks with continental scale migrations

“…As such, the potentially large number of individuals that occur on the GBR likely have a key role as large predators in coral reef environments. Studies of C. leucas in reef habitats in Fiji (Brunnschweiler and Barnett, 2013) would also support the theory that this species is a significant predator in coral reef environments. Thus, adult C. leucas would fit the definition of process links defined by Lundberg and Moberg (2003).…”

“…Recent research has indicated segregation by size may occur in C. leucas populations with smallest individuals using river habitats and largest individuals inhabiting marine regions (Simpfendorfer et al, 2005;Brunnschweiler and Barnett, 2013). Movements and habitat use by juvenile bull sharks has been well-documented in several studies (Heupel and Simpfendorfer, 2008;Heithaus et al, 2009;Heupel et al, 2010;Curtis et al, 2013), but data on adult movements are limited (Daly et al, 2014).…”

Diet shift and site-fidelity of oceanic whitetip sharks Carcharhinus longimanus along the Great Bahama Bank

“…If these activities attract whitetips to CI, this intentional and unintentional provisioning of whitetips could impact their life history. In sharks, changes in feeding behavior, aggression, and movement patterns have been suggested and/or demonstrated as a result of provisioning (Fitzpatrick et al 2011, Maljkovi & Côté 2011, Bruce & Bradford 2013, Brunnschweiler & Barnett 2013. Modification of migratory patterns in response to provisioning has been demonstrated in other shark species (Bruce & Bradford 2013), as has a lack of response to provisioning (Hammerschlag et al 2012).…”

Behaviour of aggregated grey nurse sharks Carcharias taurus off eastern Australia: similarities and differences among life-history stages and sites

“…Pierce et al 2010) and been used to formulate and/or improve management strategies to mitigate disturbances (e.g. Bruce et al 2005, Dans et al 2012. Behavioural studies have largely focused on terrestrial vertebrates, particularly birds and mam mals (Bonnet et al 2002, Jennions & Møller 2003, Ord et al 2005, and have extended to the marine environment with cetacean research dominant (e.g.…”

“…Quiros 2007, Cubero-Pardo et al 2011) and abnormal/stereotypic displays associated with provisioning tourism (e.g. Laroche et al 2007, Miller et al 2011, Brunnschweiler & Barnett 2013 for various species.…”