The IUCN/SSC Shark Specialist Group
Shark News 4: July 1995
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Editorial
Shark control measures
Shark meshing programmes have now been underway in Australia
and South Africa for several decades, from 1937 in New South Wales,
1952 in Natal and 1963 in Queensland. A number of other less well-
documented shark control initiatives (frequently short-term and
unplanned) have been undertaken elsewhere for swimmer protection,
apparently all too often as a panic or public-relations response to one
or more local shark attack incidents. Despite the potentially very high
cost of shark control programmes in relation to the risk that they pose
to the local population (Hamer 1993 suggested a risk of 1:107 or 108
for shark attack in New South Wales without beach meshing and
queried the economic rationality of the programme), the 1991 Shark
Conservation Workshop held in Sydney, Australia, appears to have
been the only international meeting to consider their results.
What has been learnt from the case studies presented in the
proceedings of this workshop (Pepperell et al. 1993), in this issue of
Shark News and from other sources?
There is a clear pattern of effect: all regular beach meshing
programmes have produced a large initial catch of sharks during the
first year or two of operation, followed by very marked decline and
then a low and relatively steady catch rate. All have successfully
protected the public, in that the (already infrequent) incidence of
shark attacks ceased or fell to a very low level after meshing.
However, none of the programmes provide much if any information
on shark population levels before or after meshing and the level of
scientific information obtained (with the notable exception of the
Natal Sharks Board programme) is generally poor. It is therefore
difficult to determine whether the methods used for shark control
were appropriate, whether judged in terms of economic costs, yield
of scientific data, or impact on dangerous sharks versus other sharks
and non-target animals. Virtually all have resulted in concern that the
control programmes, particularly when using beach meshing, may be
having unacceptable effects on by-catch including non-target sharks,
rays or threatened species such as small cetaceans and turtles.
It also seems clear that once shark control has been introduced to
areas where there is a history of shark attack (whether or not the
programme is necessary or effective), it is viewed by the beach tourist
industry and local bathing population as essential to safeguard their
continued economic health and survival. For political reasons,
therefore, it is almost impossible to abandon control programmes
once they have been initiated - a warning that it is very unwise to rush
into poorly planned and expensive responses to shark attack incidents.
It is therefore reassuring to see that shark control programmes are now
being more critically assessed and that at least some new initiatives
are being designed with more care (see opposite).
The organisers of the Second World Fisheries Congress next year
in Australia (see p.l2) plan to run a shark control programme (public
safety/swimmer protection) workshop as an adjunct to the congress,
targeted to the relatively small group of biologists and managers
involved in this field. It will be interesting to find out how attitudes
towards control programmes have changed during the five years
since the Sydney meeting as concern over the status of elasmobranch
populations, dangerous or not, has grown.
Hawaii
The following is the abstract of a paper by Wetherbee, B.M., Lowe,
C.G., and Crow, G.L. 1994. A review of shark control in Hawaii with
recommendations for future research. Pacific Science, 48(2): 95-115.
In an attempt to allay public fears and to reduce the risk of shark
attack, the state government of Hawaii has spent
over US$300,000 on shark control programmes
between 1959 and 1976. Six control programmes
of varying intensity resulted in the killing of 4,668
sharks at an average cost of $182 per shark. The
programmes furnished information on diet,
reproduction and distribution of sharks in Hawaii,
but research efforts had a number of shortcomings.
Analysis of the biological data gathered was
not directed towards the tiger shark Galeocerdo
cuvier, which is responsible for most attacks in
Hawaii. Reliable estimates of shark populations
in Hawaii cannot be made based on catch data
from control programmes because of sampling
biases. Most of the information gained from the
control programmes was not published in
reviewed journals and is not readily available to
the scientific community. The ability of the control
programmes to reduce shark populations and to
remove laree sharks from coastal waters appears
to have been stated with more confidence that is warranted, considering
seasonal changes observed in shark abundance and variable fishing
effort. Shark control programmes do not appear to have had measurable
effects on the rate of shark attacks in Hawaiian waters.
Implementation of large-scale control programmes in the future
in Hawaii may not be appropriate. Increased understanding of the
behavior and biology of target species is necessary for evaluation of
the effectiveness of small-scale control efforts, such as selective
fishing after an attack. Acoustic telemetry, conventional tagging, and
studies on population dynamics concentrating primarily on the tiger
shark may be used to obtain data about activity patterns, distribution,
and population parameters, providing information useful for reducing
the risk of shark attack in Hawaii and elsewhere.
Queensland, Australia
The following text is abstracted from Simpfendorfer, C. 1993. The
Queensland Shark Meshing Program: Analysis of the results from
Townsville, North Queensland. ln:J.Pepperell,J. West and P. Woon,
Shark Conservation. Zoological Parks Board of NSW, Australia.
Data from the Queensland Shark Meshing Program in the
Townsville area were analysed for the period 1964 to 1986. The
programme uses both anchored gillnets and baited drumlines, during
47 weeks of the year. Catch per unit effort data indicate that the
programme has reduced the populations of hammerhead, blacktip
and whaler sharks in the Townsville area by up to 80%, but has had
little effect on the population of tiger sharks (thought to be a wide
ranging species). Catches of hammerhead, blacktip and whaler
sharks were highest in spring and summer, associated with nearshore
migrations for pupping and mating. Tiger sharks showed no seasonal
variation in the catch. Drumlines are more effective than nets at
catching the more dangerous larger sharks and have a lower by-
catch. The review recommended greater use of lines to reduce
impacts on non-target species and more collection of scientific data
from the catch (the latter has been attempted since a review in 1992).
The programme was effective in its aim of reducing shark
attacks by cutting the numbers of dangerous sharks near popular
beaches: there were 11 attacks prior to its introduction in 1963, but
none subsequently. Withdrawing the programme would allow shark
numbers and the likelihood of attacks to increase. There have been
environmental effects, both on sharks and by-catch, but the species
concerned are widely dispersed and often wide-ranging, and the
areas affected by the programme are small and scattered. The effects
on populations as a whole are therefore considered to be minimal.
Shark nets in Hong Kong
Hong Kong is famous for many things ... shark attack is not generally
considered one of them. In the early 1990s, however, a number of
incidents, including several fatalities, put sharks under the spotlight and
sent government officials scurrying for a solution. The immediate reaction
was to bring in a shark hunter from Australia to catch what was believed
to be a large tiger shark (although the species was never confirmed). The
privately-funded hunt was unsuccessful, but did dissipate public concern;
an emotional response to an emotionally-charged situation.
Once the initial furore had died down, the government established
a working committee which included representatives from the police
force, fisheries, public safety, academia etc. to develop a 'shark attack
response strategy'. This was in 1994 and the absence of incidents that
year meant that this committee could discuss the issue rationally, taking
time to look at responses to similar situations elsewhere, to learn more
about what is and is not known about shark biology and attack, and to
develop a plan that responded to local concerns and needs.
Structure of shark prevention net used in Hong Kong. ®Maritime Mechanic Ltd. 1994.
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The plan that emerged included an education initiative introduced in
the swimming season of 1994. Posters and leaflets were produced to
advise the public of what to do in the event of shark sighting or attack and
a contingency plan was established to deal with such events. Swimmers
were warned of times and places to avoid swimming (based on the rather
consistent profiles of the recent attacks) and aerial surveys were conducted
at weekends. Shark exclusion nets were set-up as part of a pilot project
at three popular swimming beaches to provide protection and peace of
mind for bathers. The mesh characteristics of the netting were also
selected to minimise by-catch, which totalled little more than a few
cuttlefish and filefish last summer, according to weekly surveys by the
company contracted to supply and maintain the netting. The final plan
makes sense for Hong Kong and for addressing the apparently low risks
of shark attack in the area.
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