Variation in depth of whitetip reef sharks: does provisioning ecotourism change their behaviour? (original) (raw)
Related papers
No persistent behavioural effects of SCUBA diving on reef sharks
Marine Ecology Progress Series
Despite rapid growth in the marine tourism sector, the impacts of recreation on the marine environment are generally not well understood. Most existing studies of marine recreation ecology have focused on behavioural changes resulting from direct interactions between humans and wildlife including provisioning. However, non-consumptive, non-provisioning human impacts may also result in persistent behavioural impacts to shark populations. In this study, we examined differences in residency, abundance, and behaviour of reef sharks at Palmyra Atoll in response to long-term SCUBA diving activity, using a combination of survey techniques including baited remote underwater video systems and multi-year passive acoustic monitoring. In most locations with recreational diving operations, some level of human impact is pervasive, but on Palmyra, extractive fishing is prohibited, and scientific diving activities are concentrated on just a few sites that house long-term monitoring projects. These sites experience relatively intensive diving, while the majority of the island is entirely undived. Evidence from elsewhere has shown that sharks behaviourally respond to people in the water over short time scales, but our results indicate that this response may not persist. We did not detect differences in reef shark abundance or behaviour between heavily dived and undived locations, nor were there differences in shark residency patterns at dived and undived sites in a year with substantial diving activity and a year without any diving. Our results suggest that humans can interact with reef sharks without persistent behavioural impacts, and that well-regulated shark diving tourism can be accomplished without undermining conservation goals.
Marine Biology, 2013
Your article is protected by copyright and all rights are held exclusively by Her Majesty the Queen in Right of Australia. This e-offprint is for personal use only and shall not be selfarchived in electronic repositories. If you wish to self-archive your article, please use the accepted manuscript version for posting on your own website. You may further deposit the accepted manuscript version in any repository, provided it is only made publicly available 12 months after official publication or later and provided acknowledgement is given to the original source of publication and a link is inserted to the published article on Springer's website. The link must be accompanied by the following text: "The final publication is available at link.springer.com".
Marine Biology, 2013
The attraction or provisioning of sharks for the purpose of tourism is a lucrative and popular industry that remains controversial regarding its possible risks to target species and impacts on local ecosystems. The long-term impacts of such activities on the behaviour and movement patterns of sharks have typically been difficult to establish as most studies investigate contemporary behaviour concurrent with existing operations and thus have no comparative base from which to compare effects. We compared patterns of residency and behaviour of acoustic-tagged white sharks at the Neptune Islands in South Australia between periods before and after an abrupt and sustained doubling of cage-diving effort that occurred in 2007. The number of sharks reported by cage-dive operators significantly increased after 2007. Comparisons also revealed there were significant increases in sharks' periods of residency, the periods spent within areas where shark cagediving operations occur and changes in sharks' diel pattern of habitat use. Changes were site-specific with no significant differences in shark behaviour revealed over the same period at an island group 12 km from regular shark cagedive sites. The results suggest that cage-diving operations can lead to long-term changes in the site-specific behaviour of a highly vagile shark species which may need to be considered in the context of their conservation and in managing the impacts of the industry. Communicated by S. Connell.
Aquatic Conserv: Mar Freshw Ecosyst., 2019
1. Cage diving is the most important activity for the sustainable use of white sharks (Carcharodon carcharias). However, information related to their behaviour during ecotourism is scarce. 2. This study provides useful information for monitoring C. carcharias during cage‐diving activities around Guadalupe Island, Mexico. Surface behaviour of 106 white sharks was recorded for 87 days on‐board six cage‐diving boats in 2012, 2013, and 2014. 3. Of the observed sharks, 63% were immature specimens (n = 67) and 37% were considered mature (n = 39). Seventy‐one per cent were males (n = 75) and 29% were females (n = 31). 4. Interactions were classified into one of the 11 behaviours: parading, close inspection, horizontal attack, vertical attack, bait catching, feeding, not feeding, buoy catching, encounter, escape, and staying. 5. Parading, close inspections, and horizontal attacks were performed more often by mature males, whereas immature females performed more vertical attacks, with no differences between mature and immature males. 6. A total of 1,542 ethograms were registered. Each ethogram consisted on average of 6.3 ± 5.6 behaviours with a significant transitional pattern from horizontal attacks to parading and close inspections, and from vertical and horizontal attacks to bait being caught. 7. A pattern related to feeding in a simple stimulus response reflex was observed. The shark's length seems to play an important role in the efficiency of the attacks, presumably resulting from the experience of mature individuals. Intentional feeding should be avoided to prevent negative effects related to ecotourism. 8. This study constitutes a baseline for future research on white shark behaviour. It can be applied in other regions regardless of environmental conditions, quantity and size of the boats, and types of bait. Using this standard method could improve the monitoring, management, and conservation of this vulnerable species
Journal of Experimental Marine Biology and Ecology
Knowledge of the diel spatial ecology of wild animals is of great interest to ecologists and relevant to resource management and conservation. Sharks are generally considered to be more active during nocturnal periods than during the day; however, few studies have empirically evaluated diel variation in shark habitat use and how anthropogenic disturbances may influence these patterns. In the western central Atlantic Ocean, tiger sharks (Galeocerdo cuvier) are highly abundant in the shallow waters of the Little Bahama Bank, Bahamas. Within the northwest edge of the Bank, there is an area nicknamed "Tiger Beach," where tiger sharks are provisioned yearround at spatially discrete ecotourism dive sites spanning~1.5 km 2. In this study, we used an array of acoustic receivers encircling an area of 102.4 km 2 to evaluate for potential differences in diel spatial habitat use patterns for 42 tagged tiger sharks at Tiger Beach and the surrounding area. Using tracking data from 24 June 2014 to 13 May 2015, we evaluated spatial and diel patterns of shark activity space, centers of activity, residency and the daily proportion of sharks detected within the array. Sharks were detected during both day and night with no significant diel differences in habitat use metrics across the array, although spatial differences in residency existed. Four sharks accounted for 53.8% of residency data throughout the tracking period, with the majority of sharks primarily entering and exiting the array, except during summer months when the most of the tagged tiger sharks were absent from the array. We also found limited empirical support for hypothesized effects of provisioning tourism on tiger shark habitat use. However, additional research at finer, individual scales, may be needed to better resolve the potential influence of provisioning on tiger sharks at Tiger Beach.
The feeding of marine predators is a popular means by which tourists and tour operators can facilitate close observation and interaction with wildlife. Shark-feeding has become the most developed provisioning activity around the world, despite its controversial nature. Amongst other detrimental effects, the long-term aggregation of sharks can modify the natural behaviour of the animals, potentially increase their aggression toward humans, and favour inbreeding. During 949 diving surveys conducted over 44 mo, we investigated the ecology and residence patterns of 36 photoidentified adult sicklefin lemon sharks Negaprion acutidens. The group contained 20 females and 16 males. From this long-term survey, we identified 5 different behavioural groups that we described as ‘new sharks’ (7), ‘missing sharks’ (4), ‘resident sharks’ (13), ‘unpredictable sharks’ (5) and ‘ghost sharks’ (7). In spite of movements in and out of the area by some males and females, which were probably related to mating, the general trend was that residency significantly increased during the study, particularly in males, showing a risk of inbreeding due to the reduction of shark mobility. Intraand interspecific aggression was also witnessed, leading to an increased risk of potentially severe bites to humans. Our findings suggest the need for a revision of the legal framework of the provisioning activity in French Polynesia, which could include a yearly closure period to decrease shark behavioural modifications due to long-term shark-feeding activities.
PLoS ONE, 2013
We used acoustic telemetry to describe the patterns of vertical movement, site fidelity and residency of grey reef sharks (Carcharhinus amblyrhynchos) on the outer slope of coral reefs in Palau, Micronesia, over a period of two years and nine months. We tagged 39 sharks (mostly adult females) of which 31 were detected regularly throughout the study. Sharks displayed strong inter-annual residency with greater attendance at monitored sites during summer than winter months. More individuals were detected during the day than at night. Mean depths of tagged sharks increased from 35 m in winter to 60 m in spring following an increase in water temperature at 60 m, with maximum mean depths attained when water temperatures at 60 m stabilised around 29uC. Sharks descended to greater depths and used a wider range of depths around the time of the full moon. There were also crepuscular cycles in mean depth, with sharks moving into shallower waters at dawn and dusk each day. We suggest that daily, lunar and seasonal cycles in vertical movement and residency are strategies for optimising both energetic budgets and foraging behaviour. Cyclical patterns of movement in response to environmental variables might affect the susceptibility of reef sharks to fishing, a consideration that should be taken into account in the implementation of conservation strategies.
Effects of provisioning ecotourism activity on the behaviour of white sharks Carcharodon carcharias
Ecotourism operations which provide food to large predators have the potential to negatively affect their target species, by conditioning them to associate humans with food, or by generally altering their behavioural patterns. This latter effect could have potentially detrimental consequences for the ecosystem inhabited by the predator, because any behavioural changes could affect the species with which they interact. We present the results of an experimental study conducted from June to October 2004, which examined the effects of provisioning ecotourism on the behaviour of white sharks around a seal colony on a small island in South Africa. Although ecotourism activity had an effect on the behaviour of some sharks, this was relatively minor, and the majority of sharks showed little interest in the food rewards on offer. It is unlikely that conditioning would occur from the amount of ecotourism activity tested, because even those sharks identified supplying most of the data presented here (which may be more strongly predisposed towards conditioning, as their persistence around the boat is what allowed them to be identified) showed a nearly ubiquitous trend of decreasing response with time. Furthermore, even the sharks frequently acquiring food rewards typically stopped responding after several interactions. Consequently, moderate levels of ecotourism probably have only a minor impact on the behaviour of white sharks, and are therefore unlikely to create behavioural effects at the ecosystem level.
Biological effects, conservation potential, and research priorities of shark diving tourism
Biological Conservation, 2015
Shark diving tourism is a burgeoning, global industry. The growing perception that sharks can be worth more alive for tourism than dead in a fish market has become one of the leading contemporary arguments for shark conservation. However, there still exists concern that many aspects of shark-related tourism (e.g., provisioning) may alter natural behaviors and foraging areas, as well as pose a threat to humans by associating people with food. These concerns are largely driven by the previously limited scientific knowledge regarding the effects of shark diving tourism on shark biology, the marine environment and human interactions. Here we review and summarize previous research in these areas and evaluate the potential effects of dive tourism on shark behavior, ecology and subsequent human dimensions. To assist the development of future research, we provide a set of research questions. Taken together, we conclude that under the right conditions and if done in a precautionary, responsible manner, shark diving can provide a net conservation benefit (i.e., garnering of protective measures, raising awareness, instilling a conservation ethic) for a handful of species.
Frontiers in Marine Science, 2023
We used acoustic telemetry to investigate the roles of depth and temperature in the daytime foraging behaviours of 13 tagged pelagic thresher sharks by monitoring their fine scale vertical movements in the Philippines. Cumulatively, pelagic thresher shark dives traversed the entire water column where they encountered temperatures that ranged from 33°C at the surface to 12°C at 250 m depths throughout the day, but the movements of individuals varied in the extent of both their deep and shallow water limits. Dives were not synchronized to diurnal cycles, and periodicity reflected cycles of similar dives, the dives themselves, deviations, cruising, and individuality. Pelagic thresher shark movements between the warm surface layer and cooler waters below the thermocline (155-175 m) may reflect a common Alopiid strategy that balances maintaining tolerable ambient water temperatures with opportunities to search for and forage on spatially patchy distributions of prey.