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SAPA PR -- PIONEERING STUDY IN SOUTH AFRICA ON GREAT
WHITE SHARKS
Issued by: Dyer Island Conservation Trust
PIONEERING STUDY IN SOUTH AFRICA ON GREAT WHITE SHARKS
Gansbaai, Western Cape, South Africa - The global
population of great white sharks -
generally estimated at 3000-5000 - may have been significantly overestimated.
As a result the great white shark -
already listed as a species "vulnerable to extinction in the wild" by
the International Union for the Conservation of Nature (IUCN) - may be in
greater danger than has been previously recognised."
This is the implication of a pioneering study
conducted by marine biologists from the Dyer Island Conservation Trust (DICT)
working with the shark cage
diving company Marine Dynamics shark tours, in the world's densest population of
great white sharks at
Gansbaai, near the southern tip of Africa. The study is published in PLOS ONE
today (http://www.plosone.org/
The Trust's marine biologists conducted a non-invasive
study by collecting more than 20,000 photographs of great white shark dorsal fins
between 2007-2012 from Marine Dynamics shark tours vessel, Slashfin. As
each dorsal fin is unique to each shark, the researchers adapted a computerised fin
recognition programme previously used on dolphins to accurately identify
individual sharks.
This analysis took more than three years to complete.
Only 532 individual sharks were identified over the
five year collection period. As individual great white sharks are not resident in
Gansbaai, DICT marine biologists used open population statistics to extrapolate
their findings to estimate the number of great white sharks in this densely populated
area is most likely less than 1000 individuals.
"These results came as a surprise to everyone as
previously unpublished but widely accepted estimates based on non-computerised
photographic studies predicted the population was twice this number," a
member of the team, Alison Towner, commented.
As global population estimates of the great
white shark have
been calculated without accurate data provided by such a dorsal fin recognition
programme, the DICT's results are very worrying as they suggest that current
estimates of great white sharks numbers
may be significantly exaggerated.
The species is already classified as
"vulnerable" in the Red List issued by the IUCN, but now the Trust
believes that South Africa could - and should - take the lead in urgent,
scientific re-evaluation of the threat to the great white shark.
The founder and chair of the Trustees of the DICT,
Wilfred Chivell said: "Since 1991 when South Africa became the first
country to protect Great White sharks, South Africa has been at the forefront of the
study and conservation of the species. Now, for the first time, we have
scientific evidence that the threat is greater than was previously perceived.
At the Trust, we are contributing to the research urgently needed to allow
effective, evidence-based conservation policies and interventions. This
requires the active support of government at home - who are mandated to protect
this species - and form them to urgently develop their leadership in
international conservation forums. It is time for South Africa to take the
initiative, because time is clearly not on the side of the great white shark."
The Trust is continuing to collect data which is being
contributed to the national white shark dorsal fin database being analyzed by NMMU
Ph.D. student, Rabi'a Ryklief. This project will be the first national estimate
of white sharks based
on dorsal fin identification. Additionally, the Trust is sending their results
to international conservation organizations such as the World Wildlife Fund
through WWF SA and the IUCN and CITES in order to inform their efforts to
protect white sharks globally.
The study is published in PLOS ONE (eISSN-1932-6203)
an international, rigorously peer-reviewed, open-access, online science
publication read by researchers worldwide.
"Gauging the threat: The first population
estimate for white sharks in
South Africa using photo identification and automated software"
For the interactive infographic:
You can download an embed code for our interactive
infographic of our study here:
http://www.sharkwatchsa.com/
Comparative population sizes of other threatened
species (International Union for Conservation of Nature - IUCN Red Data List)
White rhino 20170
Cheetah 10000
Snow Leopard 4080-6500
Black rhino 4800
Tiger 3000
Great White Shark Not known (Frequently
quoted estimates 3000-5000)
About the Dyer Island Conservation Trust: www.dict.org.za
The Dyer Island Conservation Trust (DICT) was founded
in 2006 by Wilfred Chivell. The Trust delivers unique conservation and research
programmes in the fragile and critically important marine eco-system at the
southern-most tip of Africa. It strives to protect the largest surviving
colonies of the endangered African Penguin whose numbers are at an all-time
low; the globally important breeding and calving grounds of the Southern Right Whale;
and, the world's densest populations of the vulnerable Great White Shark.
About Marine Dynamics shark tours: www.sharkwatchsa.com
Marine Dynamics shark tours is a Fair Trade
accredited conservation orientated 5-star shark cage diving experience
based in Gansbaai, South Africa. Every client that joins Marine Dynamics for a
dive directly contributed to the Great White shark research programme of the
Dyer Island Conservation Trust. Marine Dynamics guarantees an accredited marine
biologist guide on every trip.
Contact details: Dyer Island Conservation Trust
Michelle Wcisel
MichelleSharkWatchSA.com
Wilfred Chivell
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