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.
Highlights
Some species popular for wildlife-tourism are elusive and can be difficult to find, providing food is often used by tourists and tour operators to attract target animals to increase the likelihood of viewing opportunities [1]
The diel timeline graph suggests that this difference is driven by C. leucas remaining at Station 1 for longer periods of time on feeding days (Fig. 3)
Aggregations of single or multiple species of sharks at small spatial scales are known to occur both naturally [25,26,27,28] and at ecotourism provisioning sites [15,29], but still relatively little is known from only a few species about their residency and movements patterns in the latter context [13,14,15,16]
Summary
Some species popular for wildlife-tourism are elusive and can be difficult to find, providing food is often used by tourists and tour operators to attract target animals to increase the likelihood of viewing opportunities [1]. The species’ seasonal departure from the feeding site is suggested to be related to reproductive activity, but it remains unknown if individuals, many of which can be reliably identified by divers using visible marks and pigmentation [18], leave the area on large-scale or stay away from the feeding site or out of sight at certain times of the year. Such information is crucial to obtain in order to eventually identify mating and nursery areas of C. leucas in Fiji and to design and implement effective conservation measures. Our results provide insight into how often, when and for how long individual C. leucas visit the feeding site in the Shark Reef Marine Reserve and surrounding areas, and in so doing provide information on the long-term behavioural response of a charismatic coastal shark species to food provisioning
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