Shark research shocker
New research from Australia points to proof that chumming keeps sharks in an area longer, suggesting this could raise the statistical chances of an attack.
The news comes after controversy erupted over the shark attack that killed Springbok bodyboarder David Lilienfeld, 20, at Kogel Bay on Thursday.
Researchers filming the documentary Shark Men in False Bay have come under fire recently for using a reported five tons of chum during their production.
The study, by the Australian equivalent of SA’s Council for Scientific and Industrial Research (CSIR), showed that chumming could lead to changes in the behaviour of white sharks.
The Commonwealth Scientific and Industrial Research Organisation (CSIRO) conducted its research off North Neptune Island in South Australia between 2010 and last year. They noted “significant changes” in white shark behaviour after 2007, when chumming increased as the shark cage diving industry expanded.
Since Lilienfeld’s death, social networks and websites have been running hot with the debate around perceived links between chumming and increased interaction with humans. And while the CSIRO report does not prove such a link – neither have local studies – it does underline that the area is murky scientifically.
The study showed that the “average residency period that individual sharks spend at North Neptune Island has increased from 11 days in 2001-2003 to 21 days in 2010-2011”. The average number of consecutive visits spent at the islands during residency periods “increased from two days in 2001-2003 to 6.5 days in 2010-2011”.
In addition, the average number of sharks seen by operators also increased – from 2.2 per day before 2007 to 3.4 per day after 2007.
The report said that while this did not mean the number of sharks had increased, it did reflect “that they are staying for longer periods, and that each individual is seen more often”.
The report suggested further that sharks were being conditioned to the extent that “daily movements of sharks have changed to more closely match the arrival and departure of shark cage dive operators”. They now arrived around the same time the operators arrived, and left when they left.
“This pattern now occurs on days where operators are present, and also on days when they are not present,” it said.
However, local scientists point out that shark cage diving boats operate for an average of 80 days a year in False Bay and 160 days in Gansbaai.
The CSIRO report recommends reducing the operating days at the Neptune islands to 200 per year, suggesting a much heavier chumming schedule.
Shark expert Lesley Rochat, from Afrioceans, said that while she had not seen the research, there was every reason to believe that if sharks behaved one way in Australia, similar behaviour would be recorded in SA.
The CSIRO report also identified several negative results, including “increased aggression between sharks if more sharks remain on site”, “distraction by tourism activities resulting in fewer opportunities to feed on seals and sea lions”, and “sharks provisioning on a food source (teaser baits) that is not as nutritious as their natural prey”.
These problems had the potential to bring about “unintentional impacts on the overall health of sharks”, and changes to the ecology of the area.
Minimising identified impacts on them and the environment within which they reside is important, particularly when the implications of such impacts are unknown,” the report said.
Concern about this grey area of science is reflected in the outpouring of anger locally at Lilienfeld’s death.
Two comments by surfers on the Wavescape surfing website’s Facebook page sum up the sentiment: “When are the damn authorities going to recognise and deal with the obvious FACT that chumming and cage diving has forever changed the feeding and migration habits of the Great White shark? Sharks no longer move away from humans and boats, they now look for humans and boats.” The other said:
- Sunday Argus