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OPERATIONAL SUMMARY:
* Vessel arrived at the location for the whale mooring, successful retrieval of the original mooring, and subsequent deployment of a new whale mooring.
Late this morning, the Aurora Australis arrived in the vicinity of one of several whale moorings which are located within the migration and feeding routes of many different whale species that frequent the waters of Eastern Antarctica over the Austral summer season.
The retrieval and deployment exercise is largely conducted by the Aurora's deck crew, led by Chief Mate Nick Jones and Bosun Joe McMenemy, using the vessel's aft trawl deck to land and re-position the large moorings. The Australian Antarctic Division's Communications and Technical Officer for the voyage, Daniel Mawson, takes charge of the technical management of the moorings, including sending out signals to the original mooring to confirm its location instructing it to release from its position suspended above the sea floor, as well as setting the new mooring to register its details with the systems aboard the ship before deployment.
After a briefing for those personnel involved, the Aurora's bridge team brought the ship into position and arranged for the ship's bathymetry and sonar equipment to be temporarily disabled so that Daniel and the deck team could listen for the mooring's response. Once a bearing had been confirmed to the mooring, the bridge moved the vessel in a slow arc away from that location and then re-confirmed the bearing a second time, before Daniel issued electronic instructions to the mooring to release. It took around twenty minutes for the mooring to appear at the surface, with the vessel moving closer, and then using its thrusters to position the mooring at the stern – where the deck crew could then grapple it aboard the trawl deck.
The moorings, when first deployed, are comprised of a large weight stack to secure them to the sea floor, long lines to permit the mooring to float mid-way through the water column, a large drum-like apparatus housing the microphones used to record whale vocalisations about the size of a household hot water heater - and two floats located several metres above the drum. The floats have a transponder which assists the ship to locate it once on the surface, as well as a strobe light in the event the mooring is recovered in darkness. Today however, conditions were relatively clear, with moderate swell passing our location.
As if the subjects of the mooring's placement somehow knew that their own underwater 'karaoke device' was about to be retrieved, several groups of whales appeared around the vessel during the exercise – some passing within 100 metres on both sides of the bridge. Most appeared to be adult Humpback whales, their distinctive dorsal fins and large tails making an impressive sight for those on the lookout for the mooring.
The whales were joined by groups of Giant Petrels and many smaller petrels and prions, as well as the odd Sooty albatross and their larger, whiter Wandering albatross cousins. These impressive masters of the Southern Oceans, with wingspans in excess of 3 metres, sailed around the ship dipping to disappear from view momentarily through each trough, then soaring back upwards in broad arcs. How these, and all other seabirds within these vast Southern latitudes, manage to survive for months on end without seeing land and how they're able to locate the same few small, isolated rocks each year when they do come ashore, is truly incredible.
The voyage has now completed its final objective, and we're on our way back to Hobart.
Cheers
Mark & Fred
Map
A map showing Australia and Antarctica. The map shows the journey of one voyage that has occured in the season, with each route highlighted in a distinct colour.