Ashmore - NOT Fin Whale but Bryde's Whale prob Omura's

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Subject: Ashmore - NOT Fin Whale but Bryde's Whale prob Omura's
From: Simon Mustoe <>
Date: Tue, 17 Nov 2009 02:14:39 +0000

Having now seen all of Rohan's images, I am confident that the animal seen at 
Ashmore Reef is not a fin whale but a Bryde's Whale. This is really interesting 
because the characteristics match Omura's Whale, which is a fairly recently 
described subspecies of Bryde's and to the best of my knowledge, not previously 
reported from Australian waters. It is however, reportedly from the east Indian 

Rohan's photos are here:

Note particularly the last three images, which are definite fin whales. This 
image is 
particularly notable. This is a classic dorsal fin shape for Fin Whale. See the 
way it is big, thick-based, and triangular. It almost seems to fall off the 
back of the animal as it rolls. The sheer girth of the dorsal fin base can also 
be seen in the pictures of animals logging in the Antarctic (second last 
image), as well as the huge distance between splash guards and dorsal.

Now back to the animal from the northwest shelf. Note, when we talk about 
Omura's, we're talking about a type of Bryde's Whale. Taxonomy on Bryde's is 
incomplete and Omura's was only described in 2003. Since getting accurate adult 
lengths depends on whaling or stranding, we don't really know. So I would not 
put great stock in any absolute indications of size in any books. It is likely 
that they vary somewhere around the length of a Bryde's Whale. Estimates from 
the time apparently varied from 15-20m, based on the length of the vessel. 
Shirihai and Jarrett say that Omura's is smaller than Bryde's, however I have 
other books that disagree. Since length is very difficult to estimate at sea - 
when you can only see small parts of an animal - there is every likelihood this 
whale was small enough to be at the large-end of Bryde's for size.

Second, the lack of rostral ridges. This is also down as a feature for Omura's 
whale, as is the white lower jaw, visible here:

This simply doesn't look like a fin whale. The dorsal is small, thin and like 
an isoceles triangle with a slight curl at the top. In fin whale it would be 
big, thick and tipped backwards off the body.

The base colour is wrong. Fin whales are an amazing steely-grey colour. This 
animal is cloaked in mottling, which is also very Bryde's whale. The 
splashguards are too small 
and the rostrum is not long and flat-enough.

There is a page with a description on fin whale here: Brett Jarrett's image also 
indicates the sheer size and length of features on this animal.
Here's info on Bryde's for comparison:

That all said, this is a very exciting discovery. Omura's whale has, to the 
best of my knowledge, not been confirmed in Australia before.



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