Monday, January 13, 2014

Big Sharks - Papers!


I've been posting fluff as I'm exceptionally busy - but several papers need urgent mentioning, so there!

First the GWS.
As everybody dealing with Sharks has known for a long time, Sharks do get cancer and more importantly, Shark cartilage is utterly useless in curing that disease. Finally, there's scientific verification of the former: here's a possibly first article describing tumors in Sharks, namely GWS' and Bronzies. And here's a synopsis with a funny quotable by DaSchiffman and a stellar pic by Ozzie Sam!

And, they live to at least 70 years!  
This is substantially longer than past estimates and finally confirms the intuition of many researchers and enthusiasts, with possible surprising differences in growth rates between males and females. 
Synopses here, here, and here!

And now the Tigers.
Much like described by several other authors for other oceans, the SoPac Tigers are equally highly migratory. Once again depending on individuals, they may be rather transient in coastal habitats and rather resident in offshore reefs, but then alternate those phases with large oceanic migrations, the latter especially by mature females. This paper by Jonathan Werry and others, among which my pal Eric describes such migrations between New Caledonia and Oz, and highlights the Chesterfields as an important pit stop and temporary habitat for adult males and subadult males and females.
Interview here, synopsis here.

And then, there's this.
Using mark-recapture, Meyer, Yannis and Co have estimated the growth rates and maximum lengths of Tigers in Hawaii. When it comes to the growth rates, this very much validates our observation that the smaller tigers grow incredibly fast, es exemplified by these two pics of Adi from 2005 (maybe 1.5m) and 2011 (a good 3m+), respectively.
Click for detail!

And the maximum size?
I am, quite frankly, highly frustrated!
Until now, I was of the opinion that Tigers could grow to 7m, possibly even longer - and now this: a paltry 4.6m in Hawaii and 5.5m globally! 

Frankly, not totally convinced.
Yes the 1957 record from likely Vietnam reported by Fourmanoir may well be unverified - but 50 years ago, we had not yet managed to obliterate the largest individuals of the largest species and with that in mind, it is not completely implausible. And let's also not forget the Shark culling programs in Hawaii that may have removed Sharks that could otherwise be larger now!
Obviously, those super sizes Sharks would likely be extremely rare, much like those fabled submarines - especially nowadays where they would have to be very lucky indeed to always manage to dodge the barrage of hooks we are throwing at them!
But like the GWS example from Oz and those new records from the Eastern coast of the US are showing, there's always the possibility of a surprise - or maybe one of those current 5m ones will have a better chance of growing even larger now that better management measures are slowly being implemented!
So fingers crossed!

Anyway, enjoy the papers!

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