Inferring trends and linkages between shark abundance and shark bites on humans for shark-hazard mitigation

Abstract

The present study aims at inferring linkages between the abundance of potentially dangerous sharks (PDSs) and shark hazard, so as to derive information about the underlying processes of shark peril off Recife, Brazil. Fishery-independent longline and drumline data collected from May 2004 through December 2014 for Carcharhinus leucas and Galeocerdo cuvier measuring ≥109cm were considered for analysis. Generalised additive models showed that the frequency of shark bites was directly proportional to and followed the same seasonal trends as PDS abundance, meeting the hypothesis that higher shark abundance may result in an increased chance of a shark bite. However, the species-specific seasonality of bull and tiger sharks seemed to follow distinct patterns. This method was helpful in comparing the abundance dynamics of the PDSs caught by the local shark hazard-mitigation program with the distribution of shark bites, so as to infer whether the species involved in the incidents were being effectively captured. Also, it provided some information about each species’ contribution to the overall dynamics in local shark hazard. However, despite being a potentially useful risk-management tool, its predictive efficacy for shark-peril mitigation may depend on the availability of abundant data spanning across wide temporal ranges.