Progress report 23 February
24th February 2010
The Antarctic whale expedition is now almost half way through its six-week voyage. After departing Wellington on 2 February, the Tangaroa travelled for eight days towards the Antarctic ice edge. The expeditioners encountered some rough weather initially, however the last few days have provided some good opportunities to launch the small boats and conduct research near the Balleny Islands.
Nine species of cetaceans have been sighted: humpback whales, Antarctic minke whales, fin whales, sei whales, sperm whales, southern bottlenose whales, killer whales, an unidentified beaked whale and hourglass dolphins. South of the Antarctic circle (60ºS) a total of 174 cetacean sightings have been logged, which represent about 309 individual animals. 45 sea bird species have also been logged.
Whale acoustic survey
Over 50 sonobuoys have been deployed so far. These units record whale vocalisations and transmit them via a radio signal back to the ship. Blue whale sounds have been detected on over half of the deployments , the most commonly recorded species by far, including a high concentration in the centre of the Ross Sea. A distinct song-like sound was recorded in the direct presence of minke whales, suggesting minkes may produce a similar, currently unidentified song that is often recorded in the Southern Ocean. Its source has been a mystery for years, but this may be the first evidence that this is an Antarctic minke whale song. The waters surrounding the Balleny Islands have been filled with the sounds of humpback whales. Sperm whales and fin whales have also been recorded.
Biopsy and photo-identification
The expedition team have collected 24 humpback biopsy samples and 27 photos of individual humpback flukes. These samples will be archived and form an important collection for improved understanding of linkages between the humpback whales on these southern feeding ground and the breeding grounds across the southwest Pacific and eastern Australia.
So far 20 tags have been deployed on humpback whales in the region of the Balleny islands. Some data has been transmitted from the tags back to the ship, showing a number of whales foraging to the east of the Balleny Islands. The satellite tagging is hoped to provide new insights into feeding behaviour, and later, as winter begins, show whale tracks from the Southern Ocean to their breeding grounds.
Research investigating whale feeding habitat and prey is also underway. Echo sounders, across a broad range of frequencies, have been acoustically sampling the water column below the Tangaroa for the entire voyage. This extensive data set will be analysed after the voyage. Phytoplankton samples have been collected at 68 sites along the research track, and net samples of animals detected on the echo sounders have been sampled on five occasions. Measurements of the physical properties of the water column have been conducted at three sites.
Approximately two weeks of research time remains before the Tangaroa commences its journey back to Wellington. The ship is currently near the Balleny Islands and is heading westwards. The expeditioners intend to concentrate their research effort in this region, with a focus on humpback and blue whales.