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
