04/01/2017 - 12:29

Summer shark focus off the mark

04/01/2017 - 12:29


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OPINION: With the hot days of summer now upon us, many Western Australians might be confused about how safe it is to head to the beach, given the state government’s mixed messages on the threat posed by sharks.

A fatal shark attack at Cottesloe Beach in October 2011 followed a fatality at Bunker Bay the previous month.

OPINION: With the hot days of summer now upon us, many Western Australians might be confused about how safe it is to head to the beach, given the state government’s mixed messages on the threat posed by sharks.

Last September, Fisheries Minister Joe Francis said white shark attacks were not more likely during the humpback whale migration from April-May to November-December.

But Premier Colin Barnett later said increasing whale numbers was a probable reason for the increase in shark fatalities.

Adding to the confusion are media warnings that the summer shark season has begun and the government should allow mass culling or the legal capture of great whites in fishing zones.

Headlines are stoking public fear while both government and private sector solutions are mostly aimed at preventing attacks during the summer months.

Nets, spotter planes and drones are among the proposals – in addition to a $500,000 trial over the next three months of two shark-detecting buoys anchored to the seabed about 400 metres off City Beach.

Most of these proposals are for use during summer, however, when the evidence suggests there are few, if any, great whites to worry about in the first place.

With the premier’s views at odds with those of his minister and the Department of Fisheries, and millions of taxpayer dollars being spent on possible solutions, is the government’s shark attack prevention strategy based on a proper understanding of when, where and why?

Shark history

Prior to 1995 (apart from a death at Jurien Bay in August 1967), there are no confirmed reports of fatal great white attacks since the early 1900s, when WA’s population was less than 20 per cent its current size.

The September 1995 fatality at Hopetoun was the beginning of WA’s attack resurgence and since then there have been 12 confirmed deaths by great whites, with a further three by unknown species but probably whites.

The timing of the great white fatal attacks since 1995 is important. Two in December, two in March, one in May, one in June, two in July, one in August, two in September, two in October and two in November – but none in January, February or April.

The Barnett government’s controversial drum line program off Perth and South West beaches from December to April 2014 caught plenty of sharks, but no great whites.

The evidence suggests that great white sharks aren’t likely to be a risk during summer, despite our crowded beaches. Fatal attacks by mature whites are more likely from May to December, despite few people swimming mid-year.

Research published in 2014 calculated WA could expect an average of two great white fatalities per year. Tragically, two deaths were recorded during the 2016 whale migration.

Shark diet

The diet of great white sharks is also important. They are a solitary animal that feeds mostly on fish until puberty, which can occur anywhere from 12 to 17 years of age when they are almost three metres in length and at which time their main food source changes to marine mammal meat.

In other words, young great whites are unlikely to have a taste for humans or anything mammalian, and it makes little sense to claim that the mature killer sharks are attracted by large schools of salmon or other fish.

There are varying estimates of great white longevity but some estimates are up to 50 years, with females believed to give birth about once every three years to between five and 10 pups that are immediately abandoned to care for themselves.

There is evidence that a full belly from feasting on a whale carcass triggers hormones that cause great whites to mate.

If true, this indicates it is their taste for whale meat that ensures survival of the species; this runs counter to claims WA’s increasing seal population is what lures great whites to our coastline. Overseas studies have shown the main diet mass of white sharks is whale.

However, seals are probably useful snacks while on the hunt for a proper meal and sex.

Whale history

After decades of slaughter by whalers on sailing ships before they were hunted with modern technology, WA’s humpback population in 1935 was estimated to be around 17,000.

Official Southern Hemisphere protection of humpbacks was enforced in 1963, by which time fewer than 600 adults were believed to have survived in WA waters.

Since then, humpback numbers have recovered at an astounding 11 per cent every year. In 1996, it was estimated that about 5,000 humpbacks migrated off the WA coast, with the latest population estimate greater than 30,000.

Other species, such as southern right and sperm whales, have recovered at between 5 and 10 per cent each year and there is speculation that total numbers of all species are approaching their natural levels prior to WA colonisation.

Adult humpbacks weigh about 40 tonnes, and if 30,000-plus are migrating along WA’s coast next year, that’s about 1.4 million tonnes of whale blubber that wasn’t in the water 30 years ago to attract great whites.

Humpbacks begin their 13,000-kilometre migratory swim from the Antarctic to the Kimberley and back in April or May.

They normally give birth in WA’s tropical waters from June to November and the first begin their swim back south around August, most hugging the shore and calm bays to protect their newborn from rough seas.

The journey south takes its toll on old and sick whales, many of which die, with their carcasses providing a feast for scavenger animals such as great whites.

State position

On the day that Mr Francis said shark attacks weren’t associated with whale migration, the Department of Fisheries released its four-year review of the South West white shark population.

The report used the word ‘whale’ just three times in its 97 pages and provided no evidence to back the minister’s misleading statement that the risk of great white attacks isn’t greater when the whales are migrating.

The study also conceded that nothing is known about the size of WA’s white shark population, nor if their numbers are increasing or decreasing.

International studies have shown that, since the 1800s, global great white numbers collapsed by between 60 per cent and 95 per cent in different oceans around the world.

It seems unlikely that, since protection in 1999, their WA numbers have exploded from such a low base within a single generation.

There is speculation that the number of WA shark attacks has increased because of our growing human population.

However, studies by the Australian Sports Commission and the Bureau of Statistics have shown that, possibly because of shark fear, the proportion of Australia’s population who swim, surf and enjoy other water-based activities fell by almost 20 per cent in the decade to 2010.

Winter solutions

The WA government has budgeted $20 million for its shark mitigation strategy and large sums of taxpayer and private money are being invested in research or infrastructure to reduce the risk in summer.

Most of the proposed solutions aren’t possible or are unlikely to withstand the weather in winter, when few people venture into the shark domain apart from surfers and divers.

Research, subsidies, inventions and similar investment should be aimed at protecting these mid-year swimmers who are actually at risk, whether it be wetsuit colours or electronic and chemical technology to protect individuals.

Mass culling or removal of their protected status might reduce the risk of great white attacks in WA during all months of the year, even though the evidence suggests many swim thousands of kilometres to roam our waters while the whales are migrating.

The renewed slaughter of another species may assuage public and voter fears about being killed by a shark, but is unlikely to reduce the hazard to surfers and divers who are otherwise happy to risk a trip to beaches in the winter months.

Why is there a reluctance to acknowledge or publicise the coincidence of increasing whale migration and shark attacks? A likely explanation is that few people are willing to believe there’s a dark side to the recovery of everyone’s favourite environmental icon – whales.

In the meantime, is it worth risking a swim at the beach this summer?

While there’s no denying there are great whites in WA waters during these sweltering months, it’s worth remembering there have been no fatalities in January or February.


Chris Gillham runs the website http://www.washarkattacks.net


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