SEARCH

SEARCH BY CITATION

We are deeply thankful for the valuable comments provided by our colleagues with regard to the shark attack prevention strategy that has been developed in Brazil. The shark attack outbreak off Recife is a relatively recent phenomenon that has had a huge impact on the local economy and social welfare (Hazin, Burgess & Carvalho, 2008). By the time local authorities realized that a shark attack mitigation strategy was necessary, due to the gravity of the problem, the global concern for the conservation of depleted shark populations was already widespread in the scientific literature (e.g. Baum et al., 2003). This context motivated us to develop a solution that would not require the removal of sharks from their populations (i.e. shark cull), which has been the main strategy used in several regions experiencing historically high rates of shark bites on humans, such as South Africa, Australia and Hawaii (Dudley & Cliff, 2010). Additionally, the performance of nearshore protective gillnets (i.e. shark meshing), which have been traditionally employed to mitigate shark peril in some regions, was not compatible with our goals because of low survival rates and the wide diversity of harmless, frequently endangered species in the catch composition (Paterson, 1990; Krogh & Reid, 1996; Dudley, 1997; Gribble, McPherson & Lane, 1998).

The philosophy behind the Shark Monitoring Program of Recife involved catching and removing potentially aggressive sharks before they entered the hazardous area to increase bather safety while minimizing deleterious impacts to the local environment. To achieve this, we initially focused on developing a fishing strategy that could provide acceptable levels of both survival and selectivity toward the target species. The combination of optimized longline and drumline gear allowed us to effectively reduce the capture of bycatch and hooking mortality (Afonso et al., 2011). Additionally, the spatial arrangement of baited hooks contributed to lure approaching sharks away from the critical area where most attacks occurred. With this strategy, we were able to reduce the rate of shark bites considerably while releasing most of the captured specimens alive. Furthermore, all potentially aggressive sharks were translocated to deeper waters and double tagged with acoustic and satellite transmitters upon release to assess their post-release behavior. This method allowed us to verify that such sharks did not move back to nearshore waters off Recife after being released and did not experience post-release mortality (Afonso & Hazin, 2014), at the same time it supplied precious information on shark movements and behavior.

The results obtained so far confirm the efficacy of the Shark Monitoring Program off Recife in reducing the incidence of shark attacks with little environmental damage, particularly when compared with shark meshing strategies. After 10 years of research, we came to the conclusion that shark culling is not necessary to mitigate shark peril off Recife. Furthermore, the fact that tagged sharks made extensive movements along the Brazilian continental shelf (Afonso, 2013) indicates that site-specific features in the region of Recife are contributing to the abnormally high rate of shark bites observed exclusively in this area (Hazin et al., 2008). Such features may include, among others, the construction of a commercial Port to the south of Recife and the presence of an alongshore channel in the most hazardous area. Therefore, local environmental factors, instead of an increase in the abundance of potentially aggressive sharks, seem to have triggered the shark attack outbreak off Recife.

The Shark Monitoring Program of Recife has been developed specifically for the local conditions, which involved specific taxa (mostly tiger and bull sharks) and environmental characteristics. Therefore, replicating this strategy elsewhere may depend on a number of adaptations that must be carefully considered. Also, as noticed by our colleagues, the fact that our mitigation strategy operates in a relatively small area results in moderate logistic requirements, which will increase if the strategy is applied to larger geographical ranges. Notwithstanding, the strategy herein introduced shows that, under certain circumstances, it is possible to mitigate the shark peril with minimum impacts to shark populations. Future directions to the Shark Monitoring Program of Recife seek to further reduce the mortality of more susceptible species by decreasing the amount of time sharks spend on the hook, an issue being currently addressed with the use of hook timers and hematological analyses. As our understanding of foraging behavior and stress physiology increases, we expect to further optimize our procedures in order to release all captured specimens alive. Moreover, the efficacy of bather protection strategies also depends on incorporating adequate public engagement policies so that beach goers can cope with such scenarios. Thus a component of environmental education should be desirably included in every shark control program, as is the case of Recife. While we continuously struggle to provide the most efficient measures to increase bather safety at hazardous shores, a striking conclusion that may be drawn from the case study of Recife is our general lack of capacity to predict the responses of the environment to the processes of anthropogenic pressure in coastal regions.

References

  1. Top of page
  2. References
  • Afonso, A.S. (2013). Bioecology and movement patterns of sharks off Recife, Brazil: applications in the mitigation of shark attack hazard. PhD thesis, University of Algarve, Faro, Portugal. Available at http://hdl.handle.net/10400.1/2872
  • Afonso, A.S. & Hazin, F.H.V. (2014). Post-release survival and behavior and exposure to fisheries in juvenile tiger sharks from the South Atlantic. J. Exp. Mar. Bio. Ecol. 454, 5562.
  • Afonso, A.S., Hazin, F.H.V., Carvalho, F., Pacheco, J.C., Hazin, H., Kerstetter, D., Murie, D. & Burgess, G.H. (2011). Fishing gear modifications to reduce elasmobranch mortality in pelagic and bottom longline fisheries off Northeast Brazil. Fish. Res. 108, 336343.
  • Baum, J.K., Myers, R.A., Kehler, D.G., Worm, B., Harley, S.J. & Doherty, P.A. (2003). Collapse and conservation of shark populations in the Northwest Atlantic. Science 299, 389392.
  • Dudley, S.F.J. (1997). A comparison of the shark control programs of New South Wales and Queensland (Australia) and KwaZulu-Natal (South Africa). Ocean Coast. Manag. 34, 127.
  • Dudley, S.F.J. & Cliff, G. (2010). Shark control: methods, efficacy, and ecological impact. In Sharks and their relatives II: biodiversity, adaptive physiology, and conservation, 1st edn: 567592. Carrier, J.C., Musick, J.A. & Heithaus, M.R. (Eds). Boca Raton: CRC Press.
  • Gribble, N.A., McPherson, G. & Lane, B. (1998). Effect of the Queensland Shark Control Program on non-target species: whale, dugong, turtle and dolphin: a review. Mar. Freshw. Res. 49, 645651.
  • Hazin, F.H.V., Burgess, G.H. & Carvalho, F.C. (2008). A shark attack outbreak off Recife, Pernambuco, Brazil: 1992–2006. Bull. Mar. Sci. 82, 199212.
  • Krogh, M. & Reid, D. (1996). Bycatch in the protective shark meshing programme off south-eastern New South Wales, Australia. Biol. Conserv. 77, 219226.
  • Paterson, R.A. (1990). Effects of long-term anti-shark measures on target and non-target species in Queensland, Australia. Biol. Conserv. 52, 147159.