Thursday, April 30, 2009

Husky Dusky? Maybe!


Remember the mystery Shark?
It's still a mystery - but at least, we've managed to narrow down the choices to two likely suspects. And having gone digging, I found some brilliant pics on Andy Murch's great Elasmodiver website.
The two suspects look like this.


That would be a Dusky (Carcharhinus obscurus) on top and a Silky (C. falciformis) below. See the alignment and the size of the fins? And that caudal keel that for so long has left everybody baffled? Except that, apparently, it aint really a proper "caudal keel"? Read below and you'll understand - it's complicated!

And now, compare them with the mystery pic on top: any preferences?

Like El Tiburon and after a knee-jerk reaction in favor of it being a Silky, I now root for the Dusky. I've never seen a Dusky, but I've seen plenty of Silkies - and although I can't quite put my finger on it, the mystery Shark just doesn't "feel" like one of them. I'm specially unconvinced by the first dorsal, but then again, who am I to say!

Talking of which, Juerg cautiously tends towards the Silky - but being the good scientist he is, he has passed on the question to a very prominent (and probably, the best) Shark taxonomist who has come back with the following.

"C. falciformis it is, nice pics."

but then, after reflection:

"I was a bit deprived of sleep when I made the call on the identification, so that your friend may be on to something.
I did a composite illustration of C. falciformis vs C. obscurus, and append it to this note for comparison with the best of your two images.

The only carcharhinids with prominent keels when alive and dead are Galeocerdo cuvier and Prionace glauca, so that your Carcharhinus when alive and swimming shows a keel but not when dead. Rather like observing a live bird in a tree through binoculars vs a live bird of the same species in hand from a mist net, and again the same species of bird as a study skin.
Fin size and shape change with growth in Carcharhinus. I was wondering about your C. falciformis in terms of second dorsal shape, position of the first dorsal, and pectoral fin shape and relative size.

Tooth shape of upper anterolateral teeth and vertebral counts are diagnostic for these species, but until we can pack underwater mini CAT-scan machines, we have to rely on dead animals to voucher live ones. Shark watching is not quite as advanced as bird-watching, but it's getting there"

There you have it! And yes, it's complicated! But fascinating, too - at least to me!
But whatever Shark that really was, the myth about Bronzies (C. brachyurus) prowling the waters of Fiji remains just that, a myth! As expected! For now!

Stuart: there you have it!
Well, sort of.

9 comments:

Stuart in Fiji said...

Thanks Mike,

I have to agree with the call "doesn't feel like a Silky", that was exactly my felling in the water!

So DUSKY it is as far as we are concerned at Matava! Very cool!

Stuart

the One called "Bitey".... said...

I have to vote for dusky, in a rather unscientific way: look at the shadowing of the musculature of all 3 pics; "mystery" and dusky seem to have the more similar forms. (While the actual musculature is likely close to identical for most carcharhinoids, the bulk and flex of these muscles may differ species to species...? I don't know, I'm making this up as I go.)

DaShark said...

Thx Terry!

as you know, I agree on the Dusky hypothesis, especially after viewing the pics.

Thing is, coloration and other optical indicators are quite useless when comparing very similar species that present no striking markings like Blacktip Reefs or Tigers. I was hopeful that the "keel" would be diagnostic but was apparently wrong.

As the scientist said, it's rather about fin size & alignment, and tooth & vertebrae counts.
For that, one typically requires specimen - and I for one am not about to go asking for one!

Anonymous said...

mexico pharmacy suboxone http://drugstore4.com/de/product/cialis-soft-tabs.html medicap pharmacy rapid city south dakota [url=http://drugstore4.com/product/ponstel.html]ponstel[/url]
jobs walgreens specialty pharmacy http://drugstore4.com/de/product/arcoxia.html washington board of pharmacy [url=http://drugstore4.com/de/product/himalaya-liv-52-drops.html]priceline pharmacy store[/url]
prilosec pharmacy http://drugstore4.com/fr/product/cefaclor.html new york pharmacy college [url=http://drugstore4.com/fr/product/dilantin.html]dilantin[/url]
celebrex pharmacy online http://drugstore4.com/de/product/himalaya-evercare-caps.html tennessee pharmacy tech jobs [url=http://drugstore4.com/fr/product/arava.html]pharmacy myrck[/url]

Anonymous said...

update download software system improve pml security driver microsoft windows http://freshoemsoftware.com/it/category-100-108/product-10576/Advanced-PDF-Repair-v1-0 Macromedia Studio MX 2004 [url=http://freshoemsoftware.com/de/category-100-108/product-27943/Excel-Sheets-Separator-10-1]Excel Sheets Separator 10 1[/url]
Syser Debugger 1.9 http://freshoemsoftware.com/it/category-13/product-19449/PowerFX-HumBox-VM1-1-0-VSTi bit torrent downloading software [url=http://freshoemsoftware.com/it/category-3/product-11394/Adobe-Acrobat-7-0-Pro]InstrumentLab VCL 4.3[/url]
dvd software http://freshoemsoftware.com/fr/manufacturer-9/product-18035/Autodesk-Lustre-2009 screen capture software [url=http://freshoemsoftware.com/fr/category-100-106/product-25243/Microsoft-BizTalk-Server-RFID-2009-x64]Microsoft BizTalk Server RFID 2009 x64[/url]
OO Defrag Server Edition 12.0 x64 http://freshoemsoftware.com/fr/category-100-106/product-26335/Hastasoft-TimOnize-Server-3-0-German PrimaSoft Check InOut Inventory Pro 2.0 [url=http://freshoemsoftware.com/de/manufacturer-9/Autodesk?page=4]camra software[/url]
handwriting software http://freshoemsoftware.com/de/category-100-103/product-10238/Adobe-InDesign-CS2 Catalyst SocketWrench dotNET Edition 6.0 [url=http://freshoemsoftware.com/de/category-200-203/product-10012/Macromedia-Fireworks-8-Mac]Macromedia Fireworks 8 Mac[/url]
time tracking software http://freshoemsoftware.com/category-200-203/product-15791/ImageDoctor-1-5-Mac outsourcing software development [url=http://freshoemsoftware.com/fr/product-17437/Coda-Mac]personal budget software[/url]

Anonymous said...

Good day!

Nowadays getting a good job is not an easy task.
If you are looking for a job check out an interesting [url=http://www.headhunterfinder.com]Headhunters [/url] directory.
Thanks to them i found a specialized headhunter and i got a new job.
Hope you find a nice job too!

Anonymous said...

Hi Piplы. Hi Piplы.Hi Piplы.Hi Piplы.Hi Piplы.Hi Piplы.Hi Piplы.Hi Piplы.Hi Piplы.Hi Piplы.Hi Piplы.Hi Piplы.Hi Piplы.Hi Piplы.Hi Piplы.Hi Piplы.Hi Piplы.Hi Piplы.Hi Piplы.Hi Piplы.Hi Piplы.Hi Piplы.Hi Piplы.Hi Piplы.Hi Piplы.Hi Piplы.Hi Piplы.Hi Piplы.Hi Piplы.Hi Piplы.Hi Piplы.

Anonymous said...

Clomiphene(Clomid) tablet
What is this medicine?

CLOMIPHENE is a fertility drug used to increase the chance of getting pregnant. It is

used to help women ovulate (produce a mature egg) properly during their cycle. Compared

to other fertility treatments, clomiphene alone does not greatly increase your chances

of having multiple babies. An increased chance of having twins may occur in roughly 5

out of every 100 women who take this medication. Occasionally clomiphene is prescribed

to men with fertility problems due to low sperm counts.

Anonymous said...

Isotretinoin capsule
What is this medicine?

ISOTRETINOIN treats severe acne that has not responded to other therapy such as antibiotics.