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14.05.2014 04:14 Age: 4 yrs
Category: AATAMS, BlueWater

Latest tracks from tagged seals provide unique data in the Southern Ocean

The Southern Ocean is one of the most important, yet least observed of marine habitats. Connecting all the world’s oceans through the Antarctic Circumpolar Current, the physical structure of the Southern Ocean profoundly influences world climate and ecology, and plays a key role in global climate.

Southern elephant seal tracks originating from the Kerguelen Islands

Weddell seals tracks from seals tagged at Scott Base, Antarctica

Since 2009/10, the IMOS Animal Tagging and Monitoring Facility has been using Southern Ocean seals as ‘samplers’. Individual animal-borne miniaturised trackers attached to the seals collect physical data such as depth, temperature, and salinity of the waters in which they forage, as well as behavioral data on the movements of individual marine animals.

In February this year, IMOS tagged 19 Southern elephant seals at the Kerguelen Islands in the southern Indian Ocean, and eight Weddell seals at Scott Base in Antarctica. At this time of year the elephant seals are accumulating resources during foraging trips in preparation for the breeding season that starts in September. Elephant seals are capital breeders, meaning that when they are ashore to give birth and suckle their pups they rely on stored resources and do not feed at all during this time. 

As can be seen from the maps (see right, click on the images to open at full size) the seals are providing nice coverage in the Ross Sea and across the southern Indian Ocean and into the southern Pacific Ocean. The Weddell seals in particular are producing “mooring-like” information at the ice edge; meaning the seals are providing multiple casts from a single area over time rather than from a wide range of sites.

Since the seals were tagged in February the elephant seals have provided 4,703 conductivity, temperature, and depth (CTD) profiles and the Weddell seals 1,447 CTD profiles in the Southern Ocean. Whilst the physical data from these profiles will feed into ocean and climate models, the data also allows biologists to gain a much better understanding of how the environment influences the seals’ foraging behaviour and success in relation to changes in the ocean around them.

Dr Sophie Bestley is using the IMOS repository of seal data to develop and evaluate statistical models that describe and predict the migration and foraging behavior of southern elephant seals and other top marine predators between sub-Antarctic islands and east Antarctic waters. She holds an ARC Super Science Fellowship under a joint project of the University of Tasmania’s Institute of Marine and Antarctic Sciences, Macquarie University and the Australian Antarctic Division.

Dr Bestley is particularly interested in incorporating the vertical dimension – animal diving behavior – into movement predictions as “analyses that incorporate at least two dimensions can test more sophisticated models of foraging behaviour”.

“A fundamental goal of animal ecology is to quantify how environmental factors influence individual movement,” she explains, “because this is key to understanding how a population can respond to future change.”

“Many species are of significant conservation concern, others are recovering from previous harvesting, some are being harvested and all will be affected by a changing climate. Our research, which aims to better describe and understand the ecology of the vast ocean to the south of Australia, will provide the information that will assist in managing this region in an era of change.”