Ausnetters,
We've just got back from a weekend spent looking for cetaceans along the
Great Ocean Road between Port Fairy and Portland.
The trip was a great success with Blue Whales seen on both days, including a
boat trip on the Sunday. Despite having favourable conditions on Saturday we
did not get out to sea. The reasons are still somewhat unclear! Instead, we
headed out for sunrise to the petrified forest at Cape Bridgewater just west
of Portland in the hope of seeing Blue Whales off the coast.
It was a cool morning with a refreshing light north easterly wind. We
trudged slightly eastwards to a cliff edge where we would get a good
panoramic view of the horizon. Within about 20 minutes we had found our
first enormous whale blow about 4 miles out to sea.
The Blues feed on krill which is super-abundant along an area of upwelling
which is most prevalent between Cape Otway and the border with South
Australia. The 'Bonney upwelling' is caused by winds that blow along the
shore from east to west during the late summer months. Instead of blowing
surface water westwards it actually causes surface water to be transported
out to sea - this phenomenon is known as Ekman transport. Deep water is
frictionally coupled to the seabed and is caused to spin with the earth's
rotation. The nearer you get to the surface of the sea, the less friction
there is as surface layers slide over each other. Essentially you get a
spiralling effect with the greatest movement at the bottom and the least
movement at the surface. The net result is that the surface tends to move
away from the coast when wind conditions are along the shore in the Otway
basin. As the surface water moves away, deeper Antarctic water from beyond
the continental shelf circulates up to fill the space and collides with
warmer coastal water. This upwelling is several degrees cooler and the
nutrients it carries are concentrated along the boundary between the water
masses. There are two principle examples of where Ekman transport fuels
upwelling and krill blooms occur: here in the Otway basin and off Monterey
Bay in California. Both areas support reliable seasonal aggregations of
feeding Blue Whales and are internationally significant for the species.
At Cape Bridgewater the whales seemed to be feeding along the edge of two
water masses and after about an hour we had managed to confirm the presence
of three Blue Whales. A brief trip to Cape Nelson yielded another baleen
whale blow probably a Blue - near the horizon.
The rest of the day was spent doing a bit of birding before an early meal, a
few beers and bed.
On Sunday morning we left Port Fairy at 6am as we wanted to get out into
deep water as early as possible. On the way out we were treated to
encounters with several Yellow-nosed Albatrosses, Black-browed Albatrosses
and a Wandering Albatross. There were also a number of Prions as well as a
Grey-backed Storm Petrel and many White-faced Storm Petrels. With only a few
hours of observation time left we decided to take a course that would loop
back around towards Portland towards a region of upwelling where Blue Whales
and a number of dolphins had been seen the day before. The following two
hours was disappointing with no dolphins and extremely low numbers of
seabirds. At about 12:30 we stopped the boat and scanned the horizon for
whale blows. The sharp eyes of Steve Anyon-Smith were the first to sight a
surface disturbance at about 2 miles followed by a single blow. We headed
slowly towards the area and were delighted to find a second whale that was
slightly 'smaller' - probably only about 20 metres long!
Both whales were Blue Whales. They were feeding and on several occasions the
larger of the two would break the surface with a pectoral fin in the air as
it rolled on its side and gulped a mouthful of krill. The two animals were
significantly different sizes and although at one point they were swimming
side by side it is only possible to speculate on whether they were a mother
and calf. The Otway Basin hasn't been identified as a place that Blue Whales
breed and in fact we do not know where they breed at all.
Identification of them as Blues was simple enough. The Blues break the
surface with a massive blow about 10 metres high. The rostrum (the
flat area in front of the splash guards) is flat and rarely breaks the
surface. The splash guards are of volcanic dimensions and protrude
ridiculously high out of the water as though they would be an encumbrance
for travelling through water (see http://www.orcaweb.org/gallery.html for
some pictures). Occasionally the smaller of the two animals
would log at the surface and the dorsal fin would be above the surface. The
larger animal often did not show the dorsal which is not unusual for Blue
Whales which are so long that they are below the surface by the time the
dorsal fin passes. The region behind the head is extraordinarily wide and
the spine appears like a massive muscular column down a broad rotund back.
The next nearest whale in size would be Fin Whale which have been recorded
in the Otway Basin occasionally. Fin Whales are generally about 20 metres
long but are far slimmer than Blues appearing more bullet shaped at the
front and are less obviously massive in proportions. From the side the Blue
Whale breaks high above the surface when it rolls forward to dive and is
usually coloured pale grey-blue
with dapples of lighter grey, the patterning of which is unique for
individual animals and will shortly be the subject of a photo-identification
study at Deakin University. Although Blue Whales are often photographed
fluking (throwing their tails in the air), this does not happen often and
wasn't observed once on Sunday. This behaviour probably depends on how deep
the whales are diving to feed.
Margi Morrice - who works on Blue Whales at Deakin University and to to whom
we are indebted for her expert advice on the trip - netted some krill
(Nyctiphanes australis) for us to have a look at; each tiny animal being
about a centimetre in length. Nytiphanes krill comprises the majority of
what the Blues feed on here.
We continued to sit, watch and marvel for about two hours during which time
the whales continued to feed before we decided to head home.
If any of my photos come out reasonably I will put them on the ORCA website
for everyone to have a look at (www.orcaweb.org) but this won't be for
perhaps a week or so. For information, I am not planning to run another of
these trips this year but maybe next year when the season comes around
again. The weather and sea conditions are generally unfavourable in this
area and we were very lucky to get a weekend like we did.
In the mean time, if you wish to see Blues this year and you are in the
area, I would recommend a trip to the Capes just west of Portland as they
have been regularly seen there in recent weeks.
Thanks to everyone who came this weekend for their patience and
understanding when we couldn't get out on Saturday and for making it
possible for everyone else, including myself, to share in this wonderful
experience.
Regards,
Simon.
_____________________________________________
Simon Mustoe - Principal
AES Applied Ecology Solutions Pty Ltd.
59 Joan Avenue
Ferntree Gully
Melbourne
Victoria 3156
AUSTRALIA
Telephone 03 9762 2616
International Telephone +61 (0) 3 9762 2616
Mobile 0405 220830
Email
Website www.onthe.net.au/ecologysolutions
Birding-Aus is on the Web at
www.shc.melb.catholic.edu.au/home/birding/index.html
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