Shark Research – Brazil looks for a better way to keep beaches shark safe

Whilst shark attacks are relatively rare, when there is a sharp increase in the number of attacks it will often provoke public outcry. Between 1992 and 2011 there was an abnormally high number of shark attacks in Recife, Brazil – around 55; the increase in attacks was owing to the development of a new port area in the region.

Whilst the Government was eager to take preventative measures against future attacks, they valued the aquatic ecosystems and understood that gill nets and longlines are non-discriminatory measures which kill species other than sharks. The Shark Monitoring Program of Recife (SMP) was set up to find a technique which could reduce shark attacks whilst causing minimal disturbance to the surrounding ecosystem.

Two researchers from Universidade Federal Rural de Pernambuco (UFRPE) looked at ways this could be achieved. They first used baiting techniques to attract sharks and then relocated problem sharks away from the hazardous area. These techniques showed a 97% reduction in the amount of attacks around the site, and reduction in the mortality rates of sharks and bycatch when compared with gillnets.

During the survey the researchers aimed to reduce the mortality rate of the sharks, as well as to reduce the mortality rate of people using the water in this region. The SMP techniques involved catching sharks using circle hooks – as oppose to the traditional J style hooks – as this lowered mortality rates in the sharks. During the relocation process steps were taken to reduce the stress caused to the sharks – such as covering their eyes with a cloth. Finally the capture and relocation of the sharks afforded the researchers the opportunity to tag the sharks. The tags proved that relocation was a suitable technique in this area, as the sharks did not return to the region after being transported.

The reduction in shark mortality rates was most prevalent in tiger sharks – in South Africa 40% of tiger sharks (Galeocerdo cuvier) are released alive, whereas using the techniques employed by SMP, 82% of tiger sharks were released alive. For the remaining shark species (including bull sharks, blacktip sharks, silky sharks etc) mortality averaged about 30% - which is still a fairly high number when we consider that many of these species are considered Near Threatened in the IUCN Red List of Threatened Species.

The notion of relocating sharks as oppose to culling them is something which this study proved can work – at least in this location. However, whilst it is refreshing to see a government attempting to protect their wildlife whilst keeping sharks away from the public, the fact remains that this study still uses hook based fishing gear to attract the sharks. If steps could be taken to reduce the mortality rate of captured sharks even further, then relocation could be a real, ecologically sound solution to removing sharks from certain areas – after all relocation techniques have been used to remove venomous snakes from properties for years and are a very successful strategy in this regard. 

Hazin, F. H. V. and Afonso, A. S. (2013), A green strategy for shark attack mitigation off Recife, Brazil. Animal Conservation. doi: 10.1111/acv.12096