2009 (Week 1) Soela Seamount Pelagic
July 14, 2009 — July 16, 2009
We set out under steam at 2am on Tuesday the 14th heading SSE towards the Soela Seamount, a distance of 217 Nm from Hobart and just within the Australian EEZ. With cruise speed varying between 7-8 knots this was expected to take about 31 hours. We passed the continental shelf slope south of Tasmania just after dawn but progress towards Soela was delayed slightly by strong winds on the evening of the 14th so we arrived at Soela by midday on the 15th (not early morning, as anticipated). This allowed several hours for birding under sail before the return north. Wind remained from the southerly quarters throughout the trip so the return to Hobart was comfortable with the swell behind the vessel. On the 16th we awoke about 50 miles north of the continental shelf slope and after a few hours heading northwest along its margin, we turned towards the Derwent via a narrow pass in the basalt cliffs of the Tasman Peninsula. Shortly after this a casing in the Blizzard's gearbox shattered, so we were forced to set sail overnight back to Hobart, arriving at 9am on the 17th.
WEATHER AND SEA CLIMATE
A ridge of high pressure was located to the north and weather was calm for the first day at sea (14th). A light southerly wind was at or below Beaufort 3. In the evening this strengthened to Beaufort 6 with the onset of a southeasterly as a weak high pressure front passed. By the morning (15th) the wind had eased to about Beaufort 2 and for the rest of the trip remained Beaufort 2 and below. Throughout the trip we had confused swells but dominated by southeasterly. Air conditions were surprisingly warm, mostly about 10-12 degrees until the final night in the Derwent when a south westerly brought a rapid fall in air temperature. Sea surface temperature was also surprisingly warm: 14 degrees off Tasmania dropping to only 13 degrees at the Soela seamount.
More detailed daily trip reports are below. As predicted, albatross numbers were quite low. With the exception of Southern Royal Albatrosses and the locally breeding Tasmanian Shy Albatrosses, most species are breeding during winter so we saw mostly juvenile birds. Close into Tasmania seabird densities were very low. We were surprised by the very small number of Common Diving Petrels and very few birds at all were present at the shelf-edge. About a day south of Tasmania bird density increased significantly but was patchy. Near the Soela seamount densities of birds were particularly high, dominated by huge numbers of prions.
The most significant find of the trip was large numbers of Broad-billed Prions. This is one of the most difficult seabirds to see in Australia and virtually unknown of at sea. We conservatively estimated 500 birds around the Blizzard on the 15th but numbers were likely to have been much higher. The finding is not only significant in terms of its rarity but also, the discovery of such a high density feeding area for the species, is a first for Australian waters. Other species highlights included Salvin's Prion (present with the Broad-bills), Grey Petrel, Blue Petrel, Light-mantled Sooty Albatross and Grey-headed Albatross.
The only cetaceans were a mixed pod of about 100 (total) Long-finned Pilot Whales and Oceanic Bottlenose Dolphins in about 1000m of water over the continental shelf slope 50 miles south of Tasmania. We turned off the engine and cruised slowly using the foresail. The whales were not particularly inquisitive but approached the vessel on a number of occasions giving everyone great views. We also encountered a few fur seals (Australian or New Zealand fur seals). One was present with the whales and dolphins, three were on the shelf on the way out of Tasmania and the rest were hauled out on the cliffs of the Tasman Peninsula.
Thanks to all those below who attended and made the trip possible and to Fred and Dave of Blizzard Expeditions for making it such an enjoyable and safe trip.
- Grant Penrhyn
- Nathan Waugh
- Stacie Ward
- Ron Broomham
- Susan Abbotts
- Xenia Dennett
- Geoffrey Jones
- Dave Stickney
- Steve Murray
After an uncomfortable night steaming into a strong southeasterly wind and swell, the conditions abated for dawn and we began about 30 miles north of the Soela seamount. At first light, there were several large prions around the back of the vessel, initially tentatively identified (in half light) as Broad-billed Prions. As the sun came up more birds appeared and remained with the vessel throughout the day. Contrary to views expressed in the field guides that these birds are "boat shy", we had them flying within feet of the vessel throughout the day. By the time we reached the seamount we had in excess of 500 birds around the boat. Inspection of photos back at shore after the trip also confirmed Salvin's Prion, in addition to Antarctic Prions, mixed in with the Broad-bills. Grey Petrels were present near the seamount, coming into berley and within a few feet of the vessel, along with over 20 White-headed Petrels throughout the day, two juvenile Grey-headed Albatross, a juvenile Salvin's Albatross and a Brown Skua. Just before dusk, two Blue Petrels passed in quick succession very close to the vessel.Read more.
After an overnight steam north, we were about 50 miles south of the Tasmanian continental shelf slope at dawn and bird density was very low. Grey-backed Storm Petrel numbers were much lower than on the outward journey (only two seen). Another Light-mantled Sooty Albatross was a highlight but remained distant. The highlight of the morning was when Stacey found a mixed pod of Oceanic Bottlenose Dolphins and Long-finned Pilot Whales. On the trip back in to the Derwent we recorded a few species not seen elsewhere in the trip, including Little Penguin, Crested Tern, Black-faced Cormorant and Kelp Gull.Read more.