Oh well.
So much for being too busy to blog.
There has been a
Shark strike in Western Australia.
From what I can discern, it very much appears to have been a
predatory attack (
Christopher???) and it comes right on the heels of Mr. Moore's decision to
preemptively ban cage diving there. The apparent reason for that politically motivated stupidity was that South Australia had
restricted cage diving there because
Barry Bruce et al had discerned that
berleying (= chumming) had caused a minimal change in GW distribution.
Nothing whatsoever to do with Shark attacks - but who gives a shit provided that one can engage in populist grandstanding, right? And
this? Indeed:
Neanderthal reactions!
Which brings me straight to the following.
I rather despise those couch farting Shark lists - but people do keep me in the loop about the rare noteworthy discussions; and so I got sent this remarkable, and provided that you got a sense of humor, incredibly witty post by the Grand Mufti of Shark behavior, non other than the forever unequaled
Doc.
I hope he doesn't mind me re-posting it
verbatim in all of its glory.
A key criticism of the ruling in Western Australia is that researchers were not able to show a causal link between shark attack and chumming at shark dives. Lets see how they might prove such a link using the scientific method. How about setting up two dive sites within say 5 km of each other. At one you use chum and feed the sharks from a feeding tube or box. At the other you attract sharks by low frequency sound attraction and again feed shark from some device that precludes odorant from getting to the test-beach 5 km distant.
Now if there are sharks around I wager they will very quickly be attracted to the baiting station due to currents which rapidly brings the olfactants to their nostrils---so you might get them trained up in just a few days. For the acoustic attractions the sharks have to be within about 500 m of the hydrophone and be fairly motivated at the time. This might take several months but eventually the sharks at both sites will be feeding regularly, and reliably but probably seasonally.
To be further certain about your experimental study population you would have to tag the sharks and possibly take genetic samples to be sure you are working with different animals at the two sites...ok it could be done. Thus you have established two relatively equal feeding sites with a control and a treatment trial....good!
So after about two years of preparations you can now set up an hypothesis: H0, the null hypothesis is that there is no statistical difference between the control and treatment groups with respect to shark attacks; H1 is the proof of the pudding---There is a statistical difference between the two.
Ahhh, but here's the rub: You would of course have to continue your trials until you collect and adequate sample size for your appropriate statistical tests that you would used to either accept or reject H1 or H0. Based only on the annual rate of shark attacks world wide, this will take on the order of 1,000 years depending on the seasonality of the sharks. Considering the paucity of attacks and the time required for a human generation, you should put in your will that for the next 50 generations your offspring must continue the experiment on a daily basis until each season ends, then start again next year when the season begins. Get my drift? So it goes for all such shark-attack research.
OK...I put it up there now you shoot it down. I personally would love to understand the motivation of why sharks bite naked apes. (see Gruber, S.H. 1988. Why do sharks attack humans? Naval Research Review 40(1):2-19.)
Bingo! :)
As I've said
all along, those musings about Shark attacks amount to nothing more than conjecture, i.e. sometimes plausible but ultimately untestable hypotheses.
But is the whole story?
Is there really no evidence whatsoever to point us one way or the other?
I believe that in fact, there is.
Yes George the great doyen of
Sesselfurzing should indeed finally
creep out from behind his desk and have a reality check by doing a couple of Shark dives; but in this specific specific case, he may even be useful by staying right where he is, smack in the middle of his
Sammelsurium of Shark attack data - and ditto for
Collier!
What I'm suggesting is this.
Get a Masters student to mine those data and to analyze
whether globally, there is any statistically relevant correlation between the location of Shark strikes and that of baited Shark dives!
Of course correlation, even if it were found, is not causation. And, this would
not be
testing the hypothesis that baiting leads to more Shark attacks. For that, one would have to proceed like Doc suggests and wait for several centuries. But it would at least give us an indication about whether the hypothesis is at least plausible and thus, worth testing!
Betcha the result it is a big fat zero!
And if so, wouldn't that be all the more surprising as common wisdom would suggest the exact contrary!
Here's the long version of why this should be the case - but if you can't be bothered, here's the synopsis.
For there to be a Shark strike, a person and a Shark need to be in the same place at the same time (dooh...) and consequently, anything increasing the rate of such encounters increases the probability for such a strike.
When it comes to baited Shark dives, it thus follows that, equally trivially
- the more Sharks are present, the higher the risk of a Shark bite
- the more divers are present, the higher the risk of a Shark bite
- the more dives are being conducted, the higher the risk of a Shark bite
- the closer the divers and the Sharks interact, and the more frequently those interactions occur, the higher the risk of a Shark bite - meaning that protocols are incredibly important!
And then there's also the element of location, i.e. where those baited Shark dives are being conducted.
They are obviously being conducted where there are Sharks (dooh...) - but often, they are even located where Sharks aggregate naturally to mate and feed, e.g. around Dyer and Seal Islands in South Africa, the Neptunes in Southern Australia, Guadalupe, etc., meaning that those places are more dangerous to start with, something one may want to consider when analyzing the data.
But then again, maybe the above is a fallacy.
Maybe Shark dives habituate the Sharks to the presence of people, meaning that they become more relaxed or "tame" and thus refrain from biting. Let's not forget that
agonistic (= essentially, defensive) behavior may well be one of the principal causes of Shark bites on divers! And if we put too many divers in the water, the Sharks may well decide to
simply go away.
Yes as always it's complicated!
So how about it.
Will those guys finally let somebody analyze those data, and will those stupid assertions be finally outed for what they really are, nothing but rubbish and completely unsupported and probably even falsified by the very data collected by the people proffering them!
PS Patric here (thanks!)
and Jillian here!
PS great comment on the attacks
here!
Jillian and Duncan - lovely people!
