Human‐induced shifts in habitat use and behaviour of a marine predator: the effects of bait provisioning in the blacktip reef shark

Abstract

While the negative effects of consumptive pressures on marine predators are well established, the effects of increasing non-consumptive activities such as wildlife tourism are still understudied. As such, the long-term effects of the provision of bait on shark behaviour are still unclear. Here, we assessed the effects of provisioning using a Control-Impact design on the spatial use and level of residency of the blacktip reef shark Carcharhinus melanopterus over a 2-year period. We used effect sizes to model the relative changes in residency between provisioning and non-provisioning sites. Sharks showed a high degree of residency and significant changes in their habitat use which persisted overnight while the activity ceased. We suggest that provisioning activities can affect species with high level of residency such as the blacktip reef shark. Further research is needed to better understand how these behavioural modifications can alter the fitness of this species. It is important to adapt shark provisioning activities to limit the induced changes in habitat use.

Social Network Analysis Reveals the Subtle Impacts of Tourist Provisioning on the Social Behavior of a Generalist Marine Apex Predator

“…It is thus unsurprising then that individuals have different site preferences within Tiger Beach, perhaps determined by timing of arrival, density of conspecifics or human presence. Wide-ranging movements may also explain why space use and diel movement patterns were found to be relatively unimpacted by provisioning in this species (Hammerschlag et al, 2017), compared to highly site-attached and resident species of elasmobranchs that exhibit marked shifts in behavior in response to provisioning (Fitzpatrick et al, 2011;Mourier et al, 2020).…”

“…At face value, shark ecotourism appears to be a conservation "winwin" providing localized protection to species, while generating local income and employment (of particular importance in developing countries) and raising public awareness of imperiled species (Apps et al, 2018). Since the initial boom of these tourism operations, considerable research effort has focused on the potential ecological impacts of this industry, resulting in a number of species-specific studies exploring the influence of shark dive tourism on movement ecology (Hammerschlag et al, 2012), residency patterns (Mourier et al, 2020), trophic ecology (Abrantes et al, 2018), community composition (Clarke et al, 2013), field metabolic rates (Barnett et al, 2016), and harmful human-wildlife encounters such as shark bites [see Brena et al (2015), Gallagher et al (2015) for reviews]. On balance, each operation, as well as each species/ecosystem response to dive ecotourism are different.…”

“…In some instances, these very characteristics might buffer these species from any persistent biological impacts. For example, individuals with large activity spaces (and no or diffuse core areas) are unlikely to be exposed to the same intensity of provisioning as site-attached sharks such as reef sharks (Mourier et al, 2020). At a well-studied dive tourism site in The Bahamas, tiger sharks (Galeocerdo cuvier) appear to neither change their long-range migratory behaviorcompared to sharks from areas unimpacted by human activitiesnor their short-term diel space use in response to provisioning (Hammerschlag et al, 2012(Hammerschlag et al, , 2017.…”

Effects of a COVID‐19 lockdown‐induced pause and resumption of artificial provisioning on blacktip reef sharks (Carcharhinus melanopterus) and pink whiprays (Pateobatis fai) in French Polynesia (East‐Pacific)

“…The provisioning of sharks and rays also raises concerns regarding the potential ecological effects on the animals. Indeed, previous studies highlighted some negative impacts such as modification of the composition of elasmobranch communities (Brunnschweiler et al, 2014 ; Meyer et al, 2009 ), reduced mobility or habitat shifts (Bruce & Bradford, 2013 ; Clua et al, 2010 ; Corcoran et al, 2013 ; Huveneers et al, 2013 ; Mourier et al, 2021 ), altered activity patterns (Barnett et al, 2016 ; Bruce & Bradford, 2013 ; Corcoran et al, 2013 ), the transmission of ectodermal parasites (Semeniuk et al, 2009 ; Semeniuk & Rothley, 2008 ), alteration of physiological characteristics (Semeniuk et al, 2009 ), and elevated intra‐ and inter‐specific competition (Brunnschweiler et al, 2014 ; Clua et al, 2010 ; Newsome et al, 2004 ; Semeniuk & Rothley, 2008 ). However, other studies did not show any significant negative impacts on ecology and behavior of targeted elasmobranchs species including white sharks ( Carcharodon carcharias ) (Laroche et al, 2007 ), Caribbean reef sharks ( Carcharhinus perezii ) (Maljković & Côté, 2011 ), tiger sharks ( Galeocerdo cuvier ) (Hammerschlag et al, 2012 ), bull sharks ( Carcharhinus leucas ) (Abrantes et al, 2018 ; Brunnschweiler & Barnett, 2013 ), and juvenile lemon sharks ( Negaprion brevirostris ) (Heinrich et al, 2021 ).…”

“…However, other studies did not show any significant negative impacts on ecology and behavior of targeted elasmobranchs species including white sharks ( Carcharodon carcharias ) (Laroche et al, 2007 ), Caribbean reef sharks ( Carcharhinus perezii ) (Maljković & Côté, 2011 ), tiger sharks ( Galeocerdo cuvier ) (Hammerschlag et al, 2012 ), bull sharks ( Carcharhinus leucas ) (Abrantes et al, 2018 ; Brunnschweiler & Barnett, 2013 ), and juvenile lemon sharks ( Negaprion brevirostris ) (Heinrich et al, 2021 ). Thus, shark provisioning appears to have differential effects depending upon practices, with hand or surface feeding facilitating the development of agonistic behavior in sharks for instance (Clua, 2018 ), and species, with resident species potentially more affected than highly mobile species (Mourier et al, 2021 ).…”