Sei whales were seen off Sydney on the scheduled Halicat pelagic trip on 12 November 2011, My analysis of them (from a combination of field observations and Raja's cracking photos) is based on the following characteristic features:
Both Fin and Brydes are therefore safely eliminated, each on numerous counts.
- Very tall, up-right and falcate dorsal fin (except the one missing most of the dorsal fin), with the leading edge about 60 deg (on fin whale it is about 45 deg; on Brydes it is also leans back more and not nearly so tall).
- Narrow base to the fin (Fin Whale and Brides have a broader base because the fin leans back further)
- Flat backed surfacing appearance with the fin appearing at the rear of the exposed back before the head submerged and not much arching (fin whale arches its back early after blowing so the head goes down quite a while before the fin appears; Brydes I'm not so familiar with but the head does sink before the fin appears)
- Down-curved rostrum in profile is evident in the photo of the half breach (characteristically straight and flat in Fin, only slightly down curved towards the very tip in Brydes)
- Fairly broad, rounded rostrum in dorsal view (narrower in Fin)
- Pale lower jaw on the left side (dark in fin which is asymmetrically coloured)
- Single rostral ridge (three in Brydes)
- Complex pale, swirly blazes on the left flank above the pectoral fin (only two narrow faint chevrons on the left side of a Fin, nothing on Brydes)
- I suspect the pink throat might also be diagnostic (assuming the photo of a breaching whale labelled Bryde's in Shirihai's field guide is really a Sei as Dion has indicated).
- Also, shallow swimming leaving a trail of foot prints in between surfacing is said (By Shirihai) to be characteristic of Sei, and is certainly not typical of Fin (pers obs).
Incredibly, I think this brings the list of Balaenoptera species seen around Sydney this year to five: Bryde's, Antarctic Minke, Dwarf Minke, Fin and Sei (though I've only seen the last 3 here myself).