Shark attacks and whale migration
in Western Australia
Australia's last whaleboat skipper Ches Stubbs warned decades ago that a recovery in whale numbers would result in great white shark attacks in Western Australia.
The resumption of fatalities since the 1990s suggests a surge in migrating humpbacks (1960s ~600 / 2018 ~40,000) and other whale species is luring their main predator/scavenger close to shore.
In May 2021: the West Australian government abandoned its drumline program off various beaches as it was deemed inefficient after catching just two great white sharks in two years (see Results of the non-lethal SMART drumline trial in south-western Australia between 21 February 2019 and 20 February 2021 - PDF 3.3mb).
The chart below shows how many tagged great whites were tracked during the two years :
The tracking supports evidence that great white sharks are mostly absent off WA's coast during summer months with a clear increase in numbers during the colder months when humpbacks migrate. Read why the 2019-2021 drumline program failed.
November 2021: A fatal great white shark attack at Port Beach near Fremantle, following two deaths in 2020 near the southern coastal town of Esperance, (see here), is a reminder of a 2014 study predicting two great white fatalities per year in WA waters (see below) after decades without deaths before whale numbers recovered. WA also had two great white fatalities in 2016.
The evidence is consistent that great white shark fatalities are an autumn/winter/spring rather than a summer problem, and the most likely cause are almost two million tonnes of migrating whales that didn't exist a few decades ago, luring great whites to hunt, scavenge and mate around their carcasses.
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 including 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.
7 May 2014: the WA government claimed success 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 15 deaths since 1995 but none were 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 18 confirmed or likely great white shark fatalities since 1995, two have been in September, three in October, three in November, two in December, one in January, none in February, two in March, one in April, one in May, one in June, 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 three great white fatalities in summer since 1995 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 April/May 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 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. There was no mention of booming whale numbers likely to attract mature great white sharks with a mammalian diet.
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.
24 January 2016: The Sunday Times newspaper reports that just one of 222 tagged great white sharks being satellite tracked through 25 buoys off the WA southern coast were detected in the first two months of summer, with the last detection in late November 2015. Late November is when the last of the migrating whale herds had departed WA waters swimming south to Antarctica, removing the whale bait that lures great white sharks close to WA's shoreline where the satellite buoys are located.
7 April 2016: The West Australian newspaper reported on a new Fisheries Department study into WA's great white sharks, claiming that: "... a number of popular myths are understood to have been debunked. Among them were that great whites follow the migration routes of whales off the WA coast ...".
16 September 2016: Review of potential fisheries and marine management impacts on the south-western Australian white shark population published by the Fisheries Department is a four year study conceding that nothing is known about the size of WA's white shark population, nor if their numbers are increasing or decreasing. Despite whales being a substantial target prey and component of the adult white shark diet, the word "whale" is used only three times in the report.
When releasing the report, WA's Fisheries Minister stated that white sharks are not more likely to attack during whale migration. This is despite only three of 18 great white fatalities from 1995 to 2020 occurring in summer months when whales aren't migrating, the beaches are crowded with swimmers and summer drum lines can't catch a single great white shark.
12 December 2017: Shark mitigation and deterrent measures was published by the Australian Senate committee of inquiry into efficacy and regulation of shark mitigation and deterrent measures. The committee dismisses any connection between recovering whale numbers and increased shark attacks, seemingly based on CSIRO advice that correlation does not prove causation and the possibility of changes in near-shore fish species preyed on by sharks. It appears the Senators are unaware that great white sharks experience a dietary change preferring mammal to fish meat when they mature.
11 December 2018: The West Australian newspaper published Shark fears as more dead whales wash up on WA coast, an "exclusive" story highlighting concerns that an increase in whale carasses along the WA coast is attracting more sharks to the state's beaches. The story points out that 44 dead whales were reported on or close to the WA coast in 2018, a big increase on previous years. Among the estimated 40,000 humpbacks migrating along the WA coast, 44 is 0.1%. The annual mortality rate of humpbacks isn't know but studies have estimated 5% (up to 20% for infants), which is approximately 2,000. That suggests about 1,956 unseen humpback carcasses are floating many kilometres off the WA coast each year.
The newspaper remains unwilling to recognise that if 44 dead whales might attract sharks, 2,000 dead whales might explain why great white sharks have been congregating along the WA coast over the past 20 years, and why the public still isn't informed that the shark threat is in the humpback migration seasons of autumn, winter and spring rather than the summer months when most people go the beach.
Learn more about whale numbers, shark numbers, attack months and other possible causes of the increase in great white shark fatalities in Western Australia.Back To Top