A spatial and environmental analysis of shark attacks on Reunion Island (1980–2017)
Introduction
The risk of shark attacks has increased dramatically worldwide in recent decades [1], from a few attacks recorded in the early 1980s to over 100 per year since the 2000s, with a relatively regular number of fatal attacks (about 10 per year). It should be stressed that the world population has increased by nearly 3 billion since 1980, with a parallel rise in the number of those who engage in water sports. Such growth in leisure activities is also explained by the improvements in living standards and the introduction of new leisure opportunities and equipment, enabling year-long activity.
In order to reach a better understanding of the risk of human-shark interaction, numerous studies have been conducted at various levels, both worldwide [1], [2], [3], [4] as well as on Reunion Island [5], [6], [7]. If sharks do play an important role in marine food webs, they likewise remain at the heart of a heated debate, with public authorities in a quandary as to necessary shark preservation against coastal recreational activities.
Coastal water sports have been practiced on Reunion Island (Western Indian Ocean) for roughly 50 years [8]. Seaside tourism has developed in parallel since the 1970s [9]. Often at the foreground of the imagery linked to tourism promotion of Reunion Island, the island's west coast symbolises the tropical beach resort ideal. Yet, as in other areas of the world, Reunion Island has not been spared of the risk of shark attacks [10]. However, it can be considered that shark attack risk for the Reunionese population and tourists visiting the island is much lower than many other risks present on the territory. Nevertheless Reunion Island is vulnerable to shark attacks as evidenced by the series of 24 attacks between 2011 and 2017, of which 9 were fatal. This uncommon succession of attacks on an area that is so small, and with marked structural social and economic vulnerability [11], has had a particular impact on Reunion's insular society [5]. The political and social malaise caused by these attacks is compounded by economic damage and indirect financial losses linked to the sharp drop in coastline use [12], [13].
This paper proposes to analyse the data relating to shark attacks on Reunion Island since 1980 (n = 57). Following a preliminary framing of Reunion Island within the world ranking of shark attacks, the environmental, contextual and individual variables will be analysed in order to find some possible explanations for the attacks. The rise in the number of attacks since 2011 will also lead to research possible variables to understand and explain this increase as well as probe into their specificities. Finally, possible correlations between explanatory and significant variables of the dataset will be assessed.
Section snippets
Study area
Reunion Island is a small island of 2512 sq km with a population of 860,000 inhabitants, located east of Madagascar (Fig. 1). This volcanic island is institutionally linked to mainland France (of which it is an Overseas Department). The climate is tropical with a cool, dry season from April to September (austral winter) and a warm, humid season from October to March (austral summer). The island's climatology is made even more complicated by its rugged terrain, several dozen micro-climates [14]
Shark attacks worldwide
The number of shark attacks has increased worldwide over the past decades. From just between 30 and 45 attacks a year (Fig. 2a) recorded in the early 1980s, the number has topped a hundred annually since the 2000s, with relative regularity in the number of fatal attacks, at around 10 per year on average. These first data taken from the Global Shark Attack File compilation database [20] are reliable and have been improved over the years. However, they include some sources of bias in their data
Conclusion
In this study of shark attacks that occurred between 1980 and 2017 on Reunion Island, database analysis (57 attacks since 1980) enables identification of several variables which might influence the occurrence of attacks. The apparently most relevant parameters in this context are the following: time of day, month, and turbidity. As for vulnerability, the type of activity performed by victims seems decisive, with swimmers and bodyboarders being the most vulnerable group for fatal attacks. Two
Acknowledgments
Our many thanks for their precious help and advice go to Dr Dominique Gay (University of Reunion Island/UR), Emmanuel Marcadé (UR), Dr. Hélène Magalon (UR), Magali Duval (Ifremer), Pr. Sébastien Jacquemet (UR), Pr. Vilasnee Tampoe-Hautin (UR) and Jean-Luc Clairambault (UR).
Conflicts of interest
None.
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