Impacts of Provisioning
In recent decades marine wildlife tourism showed a dramatic growth (Dobson 2006) and shark tourism generates millions of dollars annually worldwide (Topelko & Dearden 2005). Between 1987 – 2007 the Bahamas alone offered over 1 million shark-diver interactions (Gallagher & Hammerschlag 2011) and shark provisioning has become increasingly popular (Brunnschweiler & Barnett 2013). Since its inception in 1990 the BBFS has encountered great hammerhead sharks, Sphyrna mokarran, at various sites around South Bimini and multi-year observations found that they show periodic high site fidelity at several locations surrounding the Bimini Islands (O’Connell et al. 2015). This offers a unique opportunity to analyze the effects of provisioning on the great hammerhead sharks in the Bahamas. Our project at the Bimini Biological Field Station (BBFS) in collaboration with the Neal Watson’s Bimini SCUBA center aims to analyze the possible effects of food provisioning on small-scale movements and the behavioural ecology of the great hammerhead shark Sphyrna mokarran on Bimini, Bahamas.
Our study aims to:
1. Evaluate if there is an influence of the daily provisioning on the behaviour of local great hammerheads in Bimini?
2. Quantify if there are individual differences and to what extent habituation and or conditioning occurs in the sharks?
3. Understand the role of different environmental factors and stimuli in changing the observed behaviour.
4. Document the daily bait uptake of individual sharks and calculate an average bait weight each shark consumed by attending provisioning events.
The gained insights were then compared to acoustic monitoring data to examine space use pattern differences aiming at:
5. Describe the individual and local space use of acoustically tagged hammerheads sharks in Bimini and potential correlation between provisioning activities and local movements of the individuals.
The Hammerheads Of Bimini
Sharks are among the most endangered groups of all vertebrates (Gallagher et al. 2014). The population of the great hammerhead shark, Sphyrna mokarran, is suspected to have suffered from major declines throughout their range during the past 25 years. S. mokarran are categorised as endangered by the IUCN (International Union for the Conservation of Nature) Red List and were added to the CITES (Convention on International Trade in Endangered Species) Appendix II.
Findings demonstrating associative learning behaviours in sharks similar to those in land mammals (Guttridge et al. 2009) led to concerns that provisioning might negatively influence wild behaviours and natural ecology of free-ranging sharks (Brunnschweiler & Barnett 2013).
As a consequence an ongoing debate about potential behaviourally mediated ecosystem effects because of ecotourism and provisioning emerged. Barnett et al. (2016) outlines that wildlife tourism causes behavioural changes in numerous shark species, but if these behavioural changes have consequences for the shark’s health and/or fitness still needs to be proven.
To date, no such study has been conducted on the great hammerhead sharks, a species that is particularly susceptible to anthropogenic impacts (Abercrombie et al. 2005).
Effective conservation management calls for a comprehensive understanding of species-specific life-history patterns, physiology, behaviour and the links to the physical environment (Ricklefs and Wikelski 2002). This project offers the outstanding opportunity to advance theory by improving our knowledge of the inadequately documented movements and habitat use of the great hammerhead sharks. Results regarding the effects of provisioning on small-scale movements, health and/or fitness allow minimizing ecological risks and maximizing conservational efforts.