Shifts in the incidence of shark bites and efficacy of beach-focussed mitigation in Australia.

Shark-human interactions are some of the most pervasive human-wildlife conflicts, and their frequencies are increasing globally. New South Wales (Australia) was the first to implement a broad-scale program of shark-bite mitigation in 1937 using shark nets, which expanded in the late 2010s to include non-lethal measures. Using 196 unprovoked shark-human interactions recorded in New South Wales since 1900, we show that bites shifted from being predominantly on swimmers to 79 % on surfers by the 1980s and increased 2-4-fold. We could not detect differences in the interaction rate at netted versus non-netted beaches since the 2000s, partly because of low incidence and high variance. Although shark-human interactions continued to occur at beaches with tagged-shark listening stations, there were no interactions while SMART drumlines and/or drones were deployed. Our effect-size analyses show that a small increase in the difference between mitigated and non-mitigated beaches could indicate reductions in shark-human interactions. Area-based protection alone is insufficient to reduce shark-human interactions, so we propose a new, globally transferable approach to minimise risk of shark bite more effectively.

Combining the use of gradients and reference areas to study bioaccumulation in wild oysters in the Hunter River estuary, New South Wales, Australia.

Two approaches for measuring the effects of human activities on aquatic biota are gradient studies and comparison of impacted areas to external references. Wild oysters were sampled at 12 sites adjacent to, upstream and downstream of a steelworks in the Hunter River estuary and in two reference estuaries. Regression analyses for the Hunter indicated reduced concentrations with distance from the point source for some metals and PAHs. Data compared from the reference estuaries to the two sites nearest and the two furthest from the point source in the Hunter indicated elevated concentrations of contaminants both near the point source and on an estuary-wide basis. The gradient approach was useful in identifying the industrial effluent as a point source for bioavailable chemicals. Combining this with the use of reference estuaries provided a broad geographic context in which to interpret results from the Hunter and identified estuary-wide effects.