Monday, August 16, 2010

Hit and run in the Atlantic!

Very interesting!

Once again, some stellar stuff by Guy Harvey & Co.!
I literally stumbled across this plethora of information about Atlantic Ocean Tiger Sharks when googling for the pic of Doc in the previous post. It very much confirms the results from Hawaii insofar that Tigers roam immense ranges spanning thousands of miles. Are they proper territories? Probably not as that would imply that they are defended against conspecifics which does not seem to be the case as most tracks overlap.

The picture that is emerging is that Tigers are basically hit & run predators.
When they are not exploiting regular periodic food aggregations like the Laysan Albatross fledglings in Midway or the Turtle mating sites all across the South Pacific and probably elsewhere, they are always on the move, make a point of turning up at irregular intervals, linger for a while and then carry on. Like this research in Australia's Shark Bay shows (watch the video: cool!), they thus influence the behavior of their prey that never quite knows when they will appear and have to engage in costly avoidance behavior. Check out the research papers (bottom of page) or consult the very good synopsis in Predators as Prey by Oceana, one of the bibles of every Shark lover.
Fascinating stuff!

But what was Correia doing in July, smack in the middle of the Atlantic Ocean (click to view)???
It really is true that the more we learn, the less we know!

Which obviously brings me back to Fiji!
2010 has been an exceptional year for Tigers as so far, they have been around throughout the wet season from January to May and continue to be regular visitors at present.
This is obviously speculative, but we correlate this with this year's El Niño that led to a very dry Summer, meaning that there were no floods when the Tigers are believed to linger closer to the rivers. We're now in a La Niña, meaning that the weather will remain dry but cold until September and then likely become very wet indeed, with heightened risk of flash floods.

In brief: Tigers now, but they may well disappear towards the end of the year!
And again: this is pure speculation as we just do not dispose of enough yearly data sets to correlate our Shark sightings with ENSO!
Meaning that all I've said so far may be totally wrong!

Scarface by the way, being the usual hussy (being aplacental viviparous, she doesn't even have to wait like the other Carcharhinids), has once again gotten herself into trouble and is again very much pregnant and consequently huge - and I mean HUGE!
The way she looks, she'll be leaving us soon to engage in her usual months-long trek to her unknown pupping grounds, something we may well once try to decipher going forward.
Same-same for the big Bull ladies, some of which are are definitely rubicund and accordingly famished!

All-in-all, August diving is just great!
Stellar viz, nice cool weather, plenty of Sharks!
So, what are you waiting for...

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