Trends in global shark attacks

Abstract

Shark attacks are a global phenomenon that attracts widespread attention and publicity, often with negative outcomes for shark populations. Despite the widespread perceptions of shark attacks, trends in human water activities and shark populations are both dynamic, resulting in variable rates of shark attacks over space and time. Understanding variable trends in shark attacks may contribute to a better understanding of risk, and a more tempered response in the wake of an attack. We found that global shark attack rates are low, yet variable across global regions and over decades. Countries with low populations were found to have the highest rates of attack, while countries with high populations (U.S.A., Australia, South Africa) tended to have overall low attack rates, but also much more interannual variability. From the 1960s to the present, those countries with the highest populations also tended to be the places where attack rates have increased. Ultimately, shark attack risk is also driven by local conditions (e.g., time of day, species present); however, a global scale understanding of attack rates helps place risk into perspective and may contribute to a more scientifically-grounded discussion of sharks, and their management and conservation.

Fig 1. World map of countries (and regions) included in our analysis.

Countries (n = 14) included are shown in blue, while regions are represented by numbers (n = 7) and are areas within the USA, the Republic of South Africa, or Australia.

Fig 2. Shark attack rate (attacks per million people) from 1960–2015 for the 14 countries with the most shark attacks during this time.

Black dots indicate annual rates, the black line represents the temporal trend, and the gray region indicates uncertainty (95% credible region) around the trend.

Fig 3. Annual probabilities of an increase in shark attack rate from 1960–2015 for the 14 countries with the most shark attacks during this time.

Fig 4. Shark attack rate (attacks per million people) from 1970–2015 for 7 regions in countries with the most attacks during this time.

Black dots indicate annual rates, the black line represents the temporal trend, and the gray region indicates uncertainty (95% credible region) around the trend.

Fig 5. Annual probabilities of an increase in shark attacks rate from 1970–2015 for 7 regions in countries with the most attacks during this time.

Fig 6. Proportion of shark attacks by victim activity over time from 1960–2015.

(Diving includes Scuba diving, free diving and spearfishing; surface includes any surface or top water activities; surfing include boogie boarding and body boarding; swimming includes wading.) The widths of the 5-year periods are proportional to the sample size for the period, with thinner intervals indicating fewer samples (with 65 attacks for the period of 1975–1980 and 446 attacks for the period of 2010–2015, for reference).