World-first genetic analysis reveals Aussie white shark numbers

Rich Hillary and
Swellnet Dispatch

Of all apex predators, the white shark Carchardon carcharias (commonly known as the great white) is perhaps the most fascinating. The potential danger from (very rare) human interaction has embedded the species in our national consciousness.

Debate as to the size and status of the white shark populations across the globe is both vigorous and often contested, and it is fair to say we have never had an accurate picture. Now, for the first time we estimate that the total number of adult sharks across the Australasian region is around 2,210. We’re lacking data on juvenile sharks in one region so it’s difficult to say what the total Australasian population is, but it’s likely to be in excess of 8,000-10,000 animals.

CSIRO researchers working with Australian and New Zealand scientists in the National Environmental Science Program have used world-first genetic analysis to investigate white shark populations. The results of this project, published on Thursday in the journal Scientific Reports, are the first estimates of white shark adult population size, trend and survival rates for the Australasian region.

One fish, two fish…

The widely used aphorism in marine and particularly fisheries modelling is that counting fish is like counting trees, but you can’t see them and they move around all the time.

Until now, researchers have had to rely on patchy sources, like historical catch data. The various shark control programs do not provide usable data on relative density over time. We do have information on white shark migration and population structure from electronic tagging and previous genetic studies, but these don’t tell us about shark numbers.

To address this key problem we worked with colleagues across Australia and New Zealand to use a highly novel method called close-kin mark-recapture, first developed by CSIRO in the late 2000s to monitor southern bluefin tuna.

Close-kin mark-recapture first involves taking a tissue sample from a shark, alive or dead, obtaining a genetic profile of the animal, and than comparing it to all the other sharks and asking: are these sharks related, and if so how are they related?

Due to a number of factors, it is easier to take genetic samples from juvenile white sharks (in the 3.5 to 4m or less range) than from adults.

In the first phase, we compared the genetic data from juvenile white sharks to look for half-sibling pairs – animals who shared either a mother or a father. The half-siblings are the close-kin side of the problem. The chances of finding these pairs in the samples is determined by (a) the size of the adult population, and (b) the survival rate of adult sharks.

Higher numbers of sharks, or sharks with low survival rates, make it less likely to find siblings in the samples.

This linkage between a specific type of relatedness (half brothers or sisters) and the size and survival rate of the adult population is the mark-recapture side of the equation. In traditional wildlife tagging studies, we “mark” an animal in some way (physically or in terms of visual or genetic ID) and try to “recapture” it again sometime in the future.

The mark-recapture principle is exactly the same with this method. The key difference is that a juvenile shark carries the “mark” of its parent within its DNA, which is “recaptured” when you find a half-sibling pair. Find enough of these half-siblings, and you can estimate both adult numbers and survival rates.

Population

Currently, we believe there are two main populations of white shark in the Australasian region: the “Eastern” population, which is basically everything to the east of Bass Strait (including New Zealand), and the “Southern-Western” population, which appears to range from west of Bass Strait, around the South Australia and West Australia coasts as far north as Ningaloo Reef.

As part of phase one of the project we looked for half-siblings among 75 Eastern Australasian juvenile sharks and found 20. To give this some context, 75 samples permits 2,775 unique comparisons between animals. So less than 1% of those comparisons were siblings. We estimated that the number of adult sharks to be around 470 (with a range of 280-650), with at least 90% surviving from one year to the next. Given limited data there was no precise information on adult population trend.

The close-kin approach can only tell us about the adult population, however. To extend these estimates to total population size, we need to know something about the survival rate of juvenile sharks. Using data from around 70 juvenile sharks fitted with acoustic emitters, archived under Australia’s Integrated Marine Observing System, we estimated that juvenile sharks had an annual survival rate of around 73%.

Combining these juvenile survival estimates with the adult abundance and survival information from the close-kin analyses we estimated there to be around 4,060 (and a range of 2,500-6,750) white sharks in the whole Eastern population.

After obtaining these results from the initial data, we moved onto phase two of the project. We collected and processed more samples to obtain both more data for the Eastern population, and enough samples and half-sibling matches to estimate the adult population size in the Southern-Western region. In the East we now have 214 juvenile samples, and found 73 half-siblings; in the Southern-Western case we now have 175 samples, and found 27 half-siblings.

The revised estimates of adult population size in the East were around 750 (with a range of 470-1,030) and annual survival probabilities of 93%. Revised estimates of total population size in the Eastern region were around 5,460 (with a range of 2,909-12,802).

Our initial estimates of the Southern-Western adult population were around 1,460 (with a range of 760-2,250) and that survival probabilities were very high (in the 90% and above range, as for the East). So these estimates suggest there are almost twice as many adult white sharks in the Southern-Western population relative to the East.

Are shark populations increasing?

In Australia white sharks have been protected under the Federal Environment Protection and Biodiversity Conservation Act since 1999. Between 1995 and 1999 a national recovery plan was in effect. protected under various state legislation and subject to a national recovery plan.

We found that in both populations the adult population trend since protection has been essentially flat, with no evidence for a substantial increase or decrease. However, the picture is more uncertain when it comes to estimating population changes for younger white sharks.

White sharks take 12-15 years to mature. Assuming protection of the species reduced the juvenile mortality rate, then any such effect will not be apparent in the adult population until the next 5-10 years.

Balancing the conflicting goals of conservation and human protection is at times difficult and contentious. But, unquestionably, without being able to monitor populations effectively there is no way to resolve these questions.

Now we can monitor juveniles through electronic tagging programs, and keep track of adult populations with the close-kin method, we should finally have solved the problem of how to track the population size and status of this iconic predator.

Rich Hillary, Russ Bradford and Toby Patterson - CSIRO
Great White shark image courtesy Elias Levy/Flickr
This article first appeared on The Conversation

Comments

Blowin's picture
Blowin's picture
Blowin commented Friday, 9 Feb 2018 at 10:55am

Were the samples of fish taken focused on a neritic survey method ?

Is it possible there is a seperate population that is predominantly open ocean pelagic ?

velocityjohnno's picture
velocityjohnno's picture
velocityjohnno commented Friday, 9 Feb 2018 at 10:37am

Well done CSIRO, great stuff. This is quite groundbreaking, for now we can at least pinpoint a number of adults being out there.

A couple of points - life isn't easy for a young shark. Survivability of 1 year at 0.73, 2 years at 0.73*0.73, 3 years at 0.73*0.73*0.73, etc. If that's how you calculate it. For the young one that lined me up for a look on one of the local beachies last April (about 6ft long), good luck.

Being in Bass Straight, I wonder exactly where that line is between the East Coast Posse and the Westside Massif. (Apologies to Ali G). Is there overlap? Any genetic mixing? The line being in Gippsland would explain the submarines coming and having a bask around here, then heading west hugging the Otways and into the blue yonder.

And... the $12,802 question, just how fecund are they? Some days it really seems this number. How many km of surfable coastline on the East Coast again?

Terminal's picture
Terminal's picture
Terminal commented Friday, 9 Feb 2018 at 10:52am

Hi Rich, Russ and/or Toby.
Interesting results, any chance you could provide the link to the journal article? I would like to read it and can't seem to find it in CSIRO Publishing (assuming that's where it's published).
Cheers,
Terminal

Andrew P's picture
Andrew P's picture
Andrew P commented Friday, 9 Feb 2018 at 11:14am

The paper was published in the scientific journal Nature. Link here:

https://www.nature.com/articles/s41598-018-20593-w.pdf

Terminal's picture
Terminal's picture
Terminal commented Friday, 9 Feb 2018 at 12:36pm

Thanks for that and Nature, nice one.

Ontheroad's picture
Ontheroad's picture
Ontheroad commented Friday, 9 Feb 2018 at 12:26pm

Good to hear there's been some real data collection happening on this big question.. congrats to Rich, Russ and Toby.

It'll be interesting to see how the results will fair in 5-10 years once those juveniles enter adulthood. Are we really seeing an explosion of white shark numbers, or like the current results seem to suggest, are there different dynamics at play resulting in increased shark encounters round here...?

uncle_leroy's picture
uncle_leroy's picture
uncle_leroy commented Friday, 9 Feb 2018 at 4:37pm

It all seems a bit far fetched to me, CSIRO saying that numbers are stable with no increase v's an old salty Ab diver with 40 years water time saying interaction counts are going through the roof.
Or is CSIRO simply telling their boss (Australian government and taxpayers) what they want to hear, safety blanket to make everyone feel ok, tourism dollars keep flowing in and all the sheep are happy........
Are they the same people that said there was only 250 adult grey nurse sharks left along the entire eastern seaboard when in-fact, here were a lot more, just never spoken about for fears of resulting lockouts that came with the marine parks? https://www.facebook.com/NSWDPIFisheries/videos/273290869534281/
In the words of dory, keep swimming, keep swimming.....

Sprout's picture
Sprout's picture
Sprout commented Friday, 9 Feb 2018 at 6:09pm

What are their eating habits in a healthy environment? I've got no idea, but perhaps the Ab diver is having more interactions due to humans destroying their usual feed in deeper waters? In that scenario there could be far less sharks but with far greater human interaction?

t-diddy's picture
t-diddy's picture
t-diddy commented Friday, 9 Feb 2018 at 11:29pm

I don't mean any disrespect but your abalone diver saying he's seeing more sharks is anecdotal non-scientific evidence. It will tell you nothing about the shark population in Australasia.

gcuts's picture
gcuts's picture
gcuts commented Tuesday, 13 Feb 2018 at 3:49pm

Not just ab divers ... pro fisho's up 'n down the coast, all reporting same thing.

A lot more interaction. A LOT.

It's time to stop listening to the mainstream media, political BS and reports based on filtered data / info.

simba's picture
simba's picture
simba commented Friday, 9 Feb 2018 at 5:53pm

I heard from a reliable source that the sharks getting caught on drum lines around the Ballina and Evans area were not being reported to the Dorsal site because the state government and council were afraid of tourists cancelling their stay in the area over Xmas and it was bad for business.

simba

The Gull's picture
The Gull's picture
The Gull commented Friday, 9 Feb 2018 at 7:48pm

I noticed the numbers of drum line/ tag readings/ helicopter sightings reported on dorsal dropped off a cliff from many a week to almost zero reports over the holiday period in the Forster/ Great Lakes area. Coincidence?

velocityjohnno's picture
velocityjohnno's picture
velocityjohnno commented Saturday, 10 Feb 2018 at 2:41pm

Hope there's no truth to that - otherwise there's no point in having the ap as its results are not indicative of what's going on out there.

Quint's picture
Quint's picture
Quint commented Friday, 9 Feb 2018 at 6:23pm

Arrr...time for some of that fishin then.

freeride76's picture
freeride76's picture
freeride76 commented Friday, 9 Feb 2018 at 8:10pm

Revised estimates of total population size in the Eastern region were around 5,460 (with a range of 2,909-12,802).

Thats a might large margin of error.
And really, it makes a bit of a mockery of any claims of either population size or whether the population is increasing , at what rate or not.

Back to the drawing board CSIRO.

They should also have the intellectual honesty to admit they have no idea on whether populations are stable or increasing.

Pretty piss poor science.

bonza's picture
bonza's picture
bonza commented Friday, 9 Feb 2018 at 9:41pm

"They should also have the intellectual honesty to admit they have no idea on whether populations are stable or increasing"..

...but that is exactly what the authors did say.

"We found that in both populations the adult population trend since protection has been essentially flat, with NO EVIDENCE for a substantial increase or decrease. However, the picture is more UNCERTAIN when it comes to estimating population changes for younger white sharks".

i'd say your comment is pretty piss poor steve. have you read the paper? confirmation bias much? for someone who claims to have a science background your comment is remarkably rapid and ignorant in fire.

here is a paper researched from Australia's leading research institute published in by of the worlds most recognised and leading scientific publishers - and you straight up claim its piss poor science... within hours... big call.

simba's picture
simba's picture
simba commented Friday, 9 Feb 2018 at 8:26pm

Exactly what i was thinking,huge gap so lots of guess work by the sounds of it .... but just say there was 8000 sharks on the eastern side which to my mind is a lot ,potentially means that in the next 5 or so years there will be a big leap in numbers if 50% are females.

simba

I focus's picture
I focus's picture
I focus commented Friday, 9 Feb 2018 at 9:15pm

I am shocked at the low numbers is that a large enough population to sustain them genetic wise?

Distracted's picture
Distracted's picture
Distracted commented Friday, 9 Feb 2018 at 10:17pm

Velocity J, re the east and west posse’s. Shark 28 on the wildlife tracking page has no trouble cruising between the two crews and looks like it might be heading your way for a high five moment in a few weeks. See if this link below works
http://www.wildlifetracking.org/index.shtml?tag_id=157666&full=1&lang=

velocityjohnno's picture
velocityjohnno's picture
velocityjohnno commented Tuesday, 13 Feb 2018 at 8:56pm

a) Maybe there is just one population

b) Maybe that shark is a snitch for the East Coast Posse. Could get iced in a drive by. Like this:

http://metro.co.uk/2014/06/26/ten-year-mystery-solved-great-white-was-ea...

Clam's picture
Clam's picture
Clam commented Friday, 9 Feb 2018 at 10:35pm

Poor things are endangered species hopefully they figure out how to stop them eating people that would be cool

t-diddy's picture
t-diddy's picture
t-diddy commented Friday, 9 Feb 2018 at 11:36pm

Thanks posting these results - very interesting. I'm confused by 2 statements and was hoping for clarification:
1) "Now, for the first time we estimate that the total number of adult sharks across the Australasian region is around 2,210. We’re lacking data on juvenile sharks in one region so it’s difficult to say what the total Australasian population is, but it’s likely to be in excess of 8,000-10,000 animals." These statements seem to contradict each other..? which is 2000 or >10000?
and
2) "However, the picture is more uncertain when it comes to estimating population changes for younger white sharks." ...Aren't you sampling tissue from younger white sharks and therefore wouldn't your estimate be an over estimation?

t-diddy's picture
t-diddy's picture
t-diddy commented Friday, 9 Feb 2018 at 11:37pm

1) GOT IT - adult sharks 2.210

Dean Mc's picture
Dean Mc's picture
Dean Mc commented Saturday, 10 Feb 2018 at 12:25am

All those little sharks are just going to get bigger and my best guess is they will still be hunting fish in the gutters of popular tourist beaches. While the marine parks are providing a smorgasbord of larger fish, the sharks have no reason to leave. It is great to see some results on numbers, but I get the idea that the situation as it stands is a lot of jobs will be created to manage the new coastal aquarium. I remember what we had, and dread what we may end up having to deal with.

Quint's picture
Quint's picture
Quint commented Saturday, 10 Feb 2018 at 7:39am

Sharks were never endangered this is a hoax. Movies have been made "The Shark Con" books have been written "Shark Man" by Vic Hislop he mentions the shark attack cover up.

Its a hoax like "climate change" is. Sciemce. Water is the next Earth Guilt that's coming to our brains in fractions. Hoaxes in fractions. Agenda 2030' mind control in fact. Sciemce.

Sir Victor Coppleson would be turning in his grave over this green shark disgrace. Here's some data on shark, snake and croc deaths since 1992' Rio Earth Summit. Peter Singer et al.

https://en.wikipedia.org/wiki/List_of_fatal_shark_attacks_in_Australia
https://en.wikipedia.org/wiki/List_of_fatal_snake_bites_in_Australia
https://theconversation.com/croc-attacks-a-new-website-with-bite-20671

Here's some variety to read while the shark multiplies exponentially.

http://saturndeathcult.com/the-sturn-death-cult-part-1/
https://geopolitics.co/vital-issues/ben-fulford/nazionist-mafia-circles-...
http://allnewspipeline.com/FDA_Declares_War_Upon_America_People.php
http://www.2012-spiritual-growth-prophecies.com/age-of-aquarius.html

groovie's picture
groovie's picture
groovie commented Saturday, 10 Feb 2018 at 6:55am

If we were on the menu then it'd be like Crocs in the Nth u wouldn't go into the ocean without a cage around you! They hunt marine mammals, which humans aren't. We aren't the target but sometimes humans can be taken by mistake by a curious Great White. More people get killed by Bees every year so we need to keep it all in perspective!

Clam's picture
Clam's picture
Clam commented Saturday, 10 Feb 2018 at 9:44am

"But WA Fisheries Minister Dave Kelly says the CSIRO report shuts down previous claims by Mr Frydenberg that 'blind Freddy' could see white shark numbers had increased off WA.
Mr Kelly said the report found there was no increase in the southern-western shark population.
"It's time for Josh Frydenberg to stop playing politics and actually help us make our beaches safer," Mr Kelly said on Friday.
"On several occasions, I have asked the federal environment minister to commit more funding for research into the southern-western white shark population.
"Like so many other requests from WA, including a fairer share of GST, this request has been ignored."

http://www.watoday.com.au/wa-news/new-research-sheds-light-on-was-white-...

uncle_leroy's picture
uncle_leroy's picture
uncle_leroy commented Saturday, 10 Feb 2018 at 12:37pm

Peak numbers on the eastern side of 12,802 according to CSIRO
Approx 2,200km from just below Stanage to Wilson Prom, puts it at 5.819 whites per km of coastline.

groundswell's picture
groundswell's picture
groundswell commented Sunday, 11 Feb 2018 at 3:08pm

What are they still doing on the endangered list? cull culll cull

Tarzan71's picture
Tarzan71's picture
Tarzan71 commented Sunday, 11 Feb 2018 at 6:04pm

Yeah, I reckon we kill all the dolphins too, never met one I could trust, after that we should start hacking into baby fur seals and then them pesky whale sharks have had it coming for fucken ages....

groundswell's picture
groundswell's picture
groundswell commented Monday, 12 Feb 2018 at 3:42pm

But dolphins and fur seals and whale sharks arent as tasty as great whites and havent got as much mercury in them which is really good for the brain.

simba's picture
simba's picture
simba commented Sunday, 11 Feb 2018 at 6:30pm

Personally i think what they are doing now with the drum lines is a good thing as im pretty sure that the trauma a shark goes thru when hooked, tagged and having humans give it a hard time is something it will never forget .Time will tell.

simba

freeride76's picture
freeride76's picture
freeride76 commented Monday, 12 Feb 2018 at 4:18pm

Smart drumlines do seem to be working , as well as giving us valuable real data for scientific purposes.

Quint's picture
Quint's picture
Quint commented Monday, 12 Feb 2018 at 4:23pm

“SURFING will be banned at all Catholic schools on the North Coast for the foreseeable future.
THE Catholic Diocese of Lismore, which controls all Catholic schools from Port Macquarie to the Queensland border, has issued a ban on all open ocean surfing and surf lifesaving in response to the threat of "shark encounters".
A memo announcing the ban was sent to principals by Director of Catholic Schools David Condon on February 1.
It stated that the Catholic Schools Office had recently sought an independent risk assessment of parish schools conducting surfing and surf lifesaving in open waters, "specifically in relation to potential shark interactions".
"After consultation with the Catholic Schools Council, it has been determined that all Diocesan surfing, and Diocesan surf lifesaving in open waters conducted under the auspices of the Catholic Schools Office, will cease in 2018," the memo said.
At this stage it is unknown who conducted the independent risk assessment, nor what criteria were used.
The door was left open however for schools to conduct their own "independent assessments" of the risk
The memo listed three recommendations if schools opted to continue with ocean activities:

1. Events to be held at beaches protected with either nets or smart drumlines

2. Drones to be used at events

3. If no nets or smart drum lines are present, then the event should not proceed.

The memo emerges at the same time a new CSIRO report using world first genetic analysis estimated there were almost 5500 white sharks living off Australia's East Coast.

The estimate came with a huge margin for error, with the real number considered in the report as being anywhere from 2900 sharks to 12,800 sharks.

Less than 15% of the estimated population (750) were adults, with an estimated 73% survival rate for juveniles each year (giving them a one in four chance of death each year).

In Australia white sharks have been protected under the Federal Environment Protection and Biodiversity Conservation Act since 1999.

They take 12-15 years to mature.

Terminal's picture
Terminal's picture
Terminal commented Monday, 12 Feb 2018 at 5:15pm

That'll mean less groms in the lineup!!!

Ontheroad's picture
Ontheroad's picture
Ontheroad commented Monday, 12 Feb 2018 at 10:14pm

If catholic schools were serious about protecting children's welfare they'd issue a ban on catholic priests

John Eyre's picture
John Eyre's picture
John Eyre commented Tuesday, 13 Feb 2018 at 10:53pm

Is there a difference between the two different sharks on the east coast and the sou west population........?
What the fk is the border all about.... Why is there a borderline between Victoria and Tasmania.....?
Anyone care to try explain please do...

chin's picture
chin's picture
chin commented Tuesday, 13 Feb 2018 at 11:46pm

There have been plenty of whites tracked from NSW to SA and back. It doesn’t take them long to do the trip either

Quint's picture
Quint's picture
Quint commented Wednesday, 14 Feb 2018 at 4:59am

No shark attacks in Vic or SA anymore John. Sharks know imaginary lines now.

John Eyre's picture
John Eyre's picture
John Eyre commented Wednesday, 14 Feb 2018 at 9:10am

More information please.........
and i dont mean sharks passports....
So......they are the same species going by this quote from article;

'Currently, we believe there are two main populations of white shark in the Australasian region: the “Eastern” population, which is basically everything to the east of Bass Strait (including New Zealand), and the “Southern-Western” population, which appears to range from west of Bass Strait, around the South Australia and West Australia coasts as far north as Ningaloo Reef.'

Quint's picture
Quint's picture
Quint commented Thursday, 15 Feb 2018 at 8:44am

The only way to count sharks is shark attacks on Humans John. That is WHY the true numbers of shark attack are being covered up carefully. Its quite an elaborate charade that's been going on decades since Harold Holt's disappearance. A dive industry-police cover up (for the "greens") you will find. Sir Victor Coppleson's fine work has been poo pooed also. Why? He fixed this for us surfers!! Then all of his work was reversed. Why? What happened in 1965' and thereabouts?

Mmm..

http://www.truthlibrary.info/articles/corporate-fraud/agenda-21-depopula...

https://thewildvoice.org/new-world-order-vatican/

Michael Docherty was the first to volunteer his life for Agenda 2030' by nature. A brutal attack his last moments were horrific beyond belief. Let him who have ears hear. For Michael.

http://sharkattackfile.net/spreadsheets/pdf_directory/1992.10.01-Dochert...

westozzie's picture
westozzie's picture
westozzie commented Friday, 16 Feb 2018 at 1:18am
simba's picture
simba's picture
simba commented Friday, 16 Feb 2018 at 6:15am

Good story westozzie,balances the debate and makes more sense to me.

simba

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