Great White Elephant

By John Ogilvie

It's been a while since we looked at fisheries management in Western Australia. Things have been relatively quiet, aside from a few lawsuits and an ongoing inquiry into the effects of the demersal fishing ban.

You can read my latest piece on that here.

A related issue has been building for years without much official attention. It has become impossible to look away now.

On 28 September, a dead humpback whale washed up on City Beach. The carcass sat on the beach for days leaking blood and oil into the sand and surf, while large great whites circled just offshore. I took the photo below on 28 September.

The whale has since been removed, but experts say that sharks will likely be attracted to the area for weeks. Swanbourne, City Beach and Floreat remain closed.

This comes after three West Australians have lost their lives to shark attacks so far this year.

Steven Mattaboni, 38, was killed while spearfishing off Rottnest Island in May. Daniel Turpin, 35, was killed while spearfishing near Albany in June. Most recently , 63 year old Greg O’Neill was killed while swimming at Sorrento Beach in September, around 15 metres from shore. Just a few days before the fatal Sorrento attack, a surfer was seriously injured in an attack near Geraldton.

The data shows that attacks are becoming more frequent in Australian waters than in previous decades.

There is also the secondary problem. Recreational fishers routinely report having their catches “sharked” (i.e. bitten in half on the way up). This is now happening often enough that the government is examining shark depredation as part of the demersal fishing ban inquiry.

These are two different problems, and so they should be kept distinct. Depredation is a fisheries problem, shark attacks are a public safety question.

Another explanation?

There is a straightforward reason the beaches north of Fremantle are closed now. When a humpback whale washed up on Two People’s Bay near Albany in 2010, researchers dropped an array of acoustic receivers around it. These receivers went on to record the highest detection rates of tagged great whites anywhere in WA’s entire network (more than 80x the average of every other receiver up and down the coast).

A 2017 study by McAuley et al. was done on the movements of great whites off the coast of WA. While the study explicitly rejects the theory that great white sharks follow the humpback migration, it did find something interesting. Peak great white activity off Perth coincided with snapper spawning aggregations in Cockburn Sound, and almost half of the sharks tagged in the metro area were caught close to them.

The researchers suggested that management actions to recover stocks of snapper and other demersal fish could offer one explanation for the increase in shark activity around Perth.

What does the data show?

In 2018, CSIRO used a genetic technique to produce the first reliable estimates of great white shark numbers in Australian waters.

For the south-western population (South Australia through to north-western WA) it was estimated that there were around 1,460 adults, with a range from 760 to 2,250. It also found that the number of adults hadn’t changed much since great whites were protected in the late 1990s.

A few things stand out immediately. The estimate is eight years old, and the range is enormous (“between 760 and 2,250”).

Several politicians have now called for a reassessment of the stock.

They are right to do so.

Jim Penn, a retired fisheries scientist and WA’s former chief fisheries researcher, has called for an urgent reassessment of the state’s great white population. Dr Penn believes that WA’s numbers have been seriously underestimated , and that when applying the eastern population’s ratio of adults-to-juveniles, the west’s population of great whites could be as high as 10,000 animals.

While this is just an extrapolation based on the eastern ratio rather than a direct measurement, the point here is that nobody can tell him he's wrong, because nobody has the data to try.

Dr Penn also argues that the justification for blanket federal protection was questionable, as the southern and western stocks of great whites didn’t see the same heavy depletion as the east coast.

In 2014, the WA Department of Fisheries tested this hypothesis, and published the result as an appendix to the drumline environmental review. Researchers reconstructed great white catches back to 1938, using confidential interviews with licensed gillnet and longline fishermen, recreational fishers and even former whaling station workers. This information was modelled against logbook data.

Researchers found that great white shark mortality in WA was overwhelmingly incidental (bycatch in the demersal gillnet and longline fisheries). Estimated annual captures across the region peaked at 261 in 1988, and have since fallen to around 92 a year.

The decrease was attributed mainly to reductions in fishing effort (introduced to protect school and gummy shark stocks). Targeted commercial shark fishing effort fell by around 60%, retention of shark bycatch in other fisheries was eliminated and Perth waters were permanently closed to it.

The assessment wasn’t ambiguous, putting the south-western population in a high-likelihood range of 3,400 to 5,400 individuals. It remained above 70% of unexploited levels in every plausible scenario, and above 85% in the most likely ones.

In a single line of discussion, the Department observed that the inverse of this situation (similar types of evidence, mostly from the east coast indicating decline) was what had been used in the 1990s to list the species as vulnerable in the first place.

One size doesn't fit all

There is another element to the current data on great white shark populations and management that is missing from much of the discussion.

The 1999 EPBC listing for great whites was made on the assumption of a single Australian population. The 2014 assessment states plainly that the evidence supporting it came mostly from eastern Australia.

The problem is that genetic later genetic work (Blower et al. 2012) found this to be incorrect, and tracking has established that eastern and south-western great white sharks are two functionally separate populations, split at Bass Strait

How does it make sense to impose management restrictions on sharks in Western Australia using data drawn mostly from a distinct population on the other side of the continent?

More people=more attacks?

That same research from the Department of Fisheries found that the shark attack rate per million WA residents more than doubled between 1995/96 and 2010/11. During this same time period, the Department noted that participation in certain water activities actually fell. Participation in “surf related sports” reportedly declined from 2.1% of the population to 1.2% (according to the ABS). Through to 2010/11, the attack rate doubled while participation in surf sports fell. Nobody has repeated that analysis since, which is itself the point.

This is yet another area where more research should be done.

Flashback

In 2014, after seven deaths over three years, the Barnett government deployed drum lines along the coast of WA for a 13-week trial. The policy was ultimately scrapped because of the EPA citing a high degree of scientific uncertainty about the effect on the south-western white shark population (i.e. a lack of data about white shark stocks).

It’s worth noting that the Department’s 2014 assessment came out before the EPA’s ruling. It was an appendix to the very application the EPA was assessing.

12 years later, nothing has changed. The 2014 assessment has never been finalised. Its two main inputs (catch reconstruction and the demographic modelling) were marked “in preparation” and appear never to have been published. Nobody has repeated the exercise, and the EPBC listing has never been reviewed.

The best data we have (CSIRO’s genetic estimate) is now eight years old and carries a massive range from 760 to 2,250 adults.

The precautionary principle has degraded into a blanket prohibition. Uncertainty (brought about due to a lack of research) is used as a reason to never act.

The cost of this arrangement is borne almost entirely by people who use the water.

It should be noted that the 2014 data is from a working draft, and it was produced by a department whose minister was seeking approval for the drum line program. The catch reconstruction also rests on fishers recalling bycatch from decades prior with no obligation to have recorded numbers at the time. The paper also explicitly chose to apply the precautionary principle in favor of human safety (not that I have a problem with this).

Those are reasons why the work should be finished and independently reviewed. Not left sitting in an appendix for 12 years while the body count increases.

Where do we go from here?

I am not calling for a wholesale slaughter of sharks. On the 2014 drumline trial, it is worth noting that it killed 68 sharks (mostly tigers). No great whites were removed. Regardless of what one thinks about lethal control measures, it’s clear that version wasn’t effective.

I should also state plainly that I don’t think these animals are vermin, and I wouldn’t support treating them as such, even if it worked. A great white is not a feral cat or a fox. It’s a wild animal doing what it has done for millions of years in its own element. The question is how we manage the risk, not how we eliminate the animal.

It would also be dishonest to pretend that WA can simply reopen a commercial great white fishery. Great whites are protected as vulnerable and migratory under the federal EPBC, and Australia is also bound by several international treaties (CITES Appendix II and CMS Appendices I and II).

Even if you disagree with those policies, the point here is that it is outside of the WA government’s control.

So what can be done?

Finalise, publish and independently review the 2014 assessment and the catch reconstruction.

Repeat it with current data, and carry out a close-kin genetic estimate of the total southern-western population (not just the adults).

Formally review the EPBC listing against the results. Great whites were listed because of an observed decline. If that decline has stopped, the listing should be reviewed. It would also be worth examining if it is even prudent to apply the same protections across the entire continent (when the condition of shark populations could differ significantly).

Investigate non-lethal control measures. The SMART drum line trial on the south-west coast showed promise, recording no attacks at the beaches where it was carried out. The program should be expanded and evaluated properly.

The scandal here is not that the government is ignoring sharks. Between the inquiry, the beach closures and the catch-and-kill order issued after Sorrento, it plainly isn't. The scandal is that the state government answered this question 12 years ago, filed the answer as an appendix, and has been pleading ignorance ever since.

Do the research. Then we can talk.

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