Shark attacks and whale migration
in Western Australia
Increased great white shark attacks in Western Australia since the 1990s may be connected to the increasing number of migrating humpback and other whale species which lure their scavengers close to shore.
February 2014: read Western Australian Coastal Shark Bites: A risk assessment (PDF 1.5mb), a study published in the Australian Medical Journal by Professor Peter Sprivulis from the Department of Emergency Medicine at the University of Western Australia.
Conclusion: As whale abundance increases off the coast of Western Australia, it is reasonable to predict that, in the absence of effective personal or policy based risk mitigation, the risk of white shark bite when undertaking recreational water activities off the southwest coast of WA will continue to increase. However, the risk of shark bite for beachgoers engaged in bathing activities less than 25m from shore in shallow water during the WA summer, is likely to remain very low, and well below the risk of other recreational activities commonly undertaken in WA.
The paper estimates that WA may expect a mean of 8.6 shark bites and two shark bite fatalities per year from 2014 to 2018, with individual risk ratios tabulated below:
The Australian newspaper, 13 February 2014 was the first and only print media to correctly inform the public about the Sprivulis study findings and the correlation between great white shark attacks and WA's whale migration season.
The WA Government maintains the link between whales and great white sharks is not proved so the AMJ paper has been ignored.
In December 2013, the West Australian government began a program of baited drum lines one kilometre offshore from popular Perth and south-west beaches to catch sharks from January to April 2014.
Under the 2013/14 trial program, in WA's southern waters a commercial fisherman was paid to kill any sharks above three metres within the monitored areas, and Fisheries Department staff looked after drum lines off metropolitan beaches. Adequately large great white, tiger and bull sharks in these areas were hooked and destroyed until 30 April 2014 through an interim exemption under Australia's Environmental Protection and Biodiversity Conservation Act and two separate WA conservation and fish resource management laws.
7 May 2014: the WA government claimed success (desktop site) for its Shark Hazard Mitigation program with drum lines off Perth and south-west beaches from December to 30 April 2014 catching 172 sharks, 82 dead, and WA Department of Fisheries results showing almost all were tiger sharks. No sharks caught were the killer species, great whites. Tiger sharks are the confirmed killer in just one attack since 1995 (Geraldton 1997). Great white sharks were responsible for at least 10 deaths since 1995 but none have been caught in the government's cull program because there are no whales and thus few if any great whites to be caught in summer or early autumn.
11 September 2014: the Environmental Protection Authority (desktop site) recommended against continuation of the WA Government's drum line strategy and in October the government abandoned its plans to maintain the shark cull, which will not alter public risk because great white sharks are mostly absent from coastal waters in the spring and summer months when the drum lines were to be set. Oddly, the EPA recommendations acknowledge that great white sharks follow migrating whale herds but dismiss any correlation with attack risk during different seasons.
Among WA's 12 confirmed or likely great white shark fatalities since 1995, two have been in September, two in October, two in November, one in December, none in January, none in February, two in March and none in April, with two in July and one in August.
WA Fisheries Department research published in June 2014 suggests between 3,400 and 5,400 great white sharks inhabit coastal waters between Victoria and WA's North West Cape.
The WA Department of Fisheries and the government are well aware that a majority of great white attacks occur during the whale migration season in winter and spring. The charts below are extracted from A correlation study of the potential risk factors associated with white shark attacks in Western Australian waters published in November 2012.
Frequency of attacks vs season and victims’ activities
Validated white shark records July 1994 – July 2012
There have been only two shark attack fatalities in summer since 1995, one by a great white, yet the government and media ignore the whale season correlation so the public is unnecessarily frightened from swimming and exercising during summer.
This website researches evidence that great whites are lured from the deep waters of the Indian and Southern oceans to roam near whales close to the WA shoreline, with the risk of swimmer fatalities increasing during the humpback migration season from May/June to November/December.
There are other factors influencing WA's rapid increase in shark attacks but there has been almost no public or government consideration of the role played primarily by the recovery of humpback whales, which migrate 13,000 kilometres from Antarctica to the Kimberley and back each year, as well as other species such as right and sperm whales in more southerly waters.
This website does not assert that the connection between whale numbers and shark attacks is conclusive but seeks only to present evidence and spark debate or research in the absence of any media discussion.
Follow the links at the top of the page and give it some thought. WA's increased shark sightings and attacks would logically be related to a huge increase in whale numbers.
November 2012: The WA Fisheries Department has released A correlation study of the potential risk factors associated with white shark attacks in Western Australian waters (PDF download) as part of its study into the cause of increased shark attacks.
The study authors may as well have copied this website (launched in October 2012) as their conclusions are the same about the attraction of great white sharks to whale carcasses, likely seasons for attacks and an unlikely connection to seal and sea lion colonies.
The exception is that the Fisheries Department has done no published research into the correlation with booming whale numbers and the study only mentions them once - "The winter and spring period also corresponds with whale migration season. While this may be coincidental, White Sharks are known to feed on whales so caution should be exercised near a whale carcass or other such attractant."
The department fails to consider that great whites are likely to be near a whale carcass but equally likely to be attracted to a region where there's a good chance of finding one - i.e. WA's coastline during the whale migration season when there are a lot more whale calves and adult carcasses than there used to be.
December 2012: The West Australian and The Australian newspapers published WA shark stories on 22 December, one noting a swimmer decline at Perth beaches because of shark fear and the other reporting a Fisheries Department theory that record hot tropical currents off the WA coast in 2010/11 pushed cold water closer to the coast along with different fish species hunted by sharks. Ssshhh ... don't mention the whales.
July 2013: WA shark experts clash over increasing great white numbers with a former WA Fisheries Department boss acknowledging that recovering whale numbers are the cause. A former West Australian Fisheries Minister has also acknowledged that growing whale numbers are a contributor to increasing shark attacks. One expert predicts that numbers of mature great white sharks will increase off the WA coast in coming years because of their recovery since being protected in the late 1990s. However, he says this recovery in adult sharks isn't responsible for WA's spate of fatal attacks in recent years because there hasn't been enough time for juvenile stocks to reach maturity. This is correct but the reason for the shark attacks is described as a mystery, again failing to recognise the far more rapidly recovering whale herds migrating close to WA's coast that are a prized food source for adult great whites.