DOI: 10.15468/11aicq
title: Winter Foraging Locations Of Southern Ocean Predators - sub-Antarctic islands 2008/09

description: Metadata record for data expected from ASAC Project 2940 See the link below for public details on this project.

Public:
The extent of Antarctic winter sea-ice influences all aspects of the Antarctic marine food-web. We will use natural variations in inter-annual ice extent, to assess how a key component of that ecosystem, the predators, use the sea ice zone. Core foraging areas and dietary signals for a key Antarctic predator (Antarctic fur seal) will be identified. We will use newly developed, technology to track the animals, and stable isotopes to examine tropic linkages. Combined with satellite-derived sea-ice data, this will lead to the development of a model to predict how changing sea-ice patterns will influence Antarctic marine predator communities.

Project Objectives:
1. Use large samples of newly-developed (and tested) animal-borne miniature geolocating light level recorders to population level information on the spatial extent of movements of Antarctic fur seals, thereby quantifying the extent of the use of the winter pack-ice and associated waters by these abundant predators.
2. To quantify how changes in winter ice extent influence the location of core foraging areas for this species.
3. To develop models to investigate how changing ice conditions in the future will influence the movements of this species and to examine a range of climate-change scenarios.

Taken from the 2007-2008 Progress Report:
No field work was conducted at Macquarie Island in the last 12 months. This was due to the decision by the state government to not issue permits for the work.

With the help of our colleagues from BAS we did however manage to deploy 20 GLS light loggers on Antarctic fur seals at South Georgia.

Taken from the 2008-2009 Progress Report:
Objective 1 has been revised to the study of Antarctic fur seals only (see below). Research is progressing well with 78 animals tracked in 2008 and a further 80 expected in 2009.
Objectives 2 and 3 will follow once field data is available for both years (May 2010).
Isotopic analysis of blood and whisker samples for the 2008 season will commence in May 2009 once samples have been received.

Taken from the 2010-2011 Progress Report:
Public summary of the season progress:
This study has quantified the response of the Antarctic fur seal (Arctocephalus gazella) to inter-annual variation in oceanographic and winter ice conditions. We have measured the winter spatial foraging patterns of 66 adult females from three circum-Antarctic populations over two years (2008, 2009) during 114 trips to sea, while simultaneously recording in situ water temperature. Stable isotope analysis of fur seal blood and whisker samples indicates that adult females feed on a range of lower (krill) to higher (fish and squid) trophic levels across their winter range. Broad-scale habitat preferences across the range of the species indicate the importance of shelf, ice edge, frontal and oceanic and continental upwelling features in determining winter foraging movements.Quality: Values provided in spatial and temporal coverage are approximate only.

Taken from the 2008-2009 Progress Report:
Variations to work plan or objectives:
Since the original submission of the proposal the project has undergone a change of focus due to logistic constraints imposed by the vertebrate pest eradication plan at Macquarie Island. The revised project objectives now relate to the influences of climate and oceanographic variability including changes in sea-ice extent, on the winter foraging behaviour and habitat use of the Antarctic fur seal, a numerous component of the Antarctic foodweb. Research is being undertaken at three sites with the collaboration of UK, US and South African scientists.

The changes necessitate a reduction in the power of predictions pertaining to Southern Ocean trophic models. However the project will provide much needed insight into the winter behaviour of one of Antarctica's most numerous marine predators.

Field work:
In 2007/8, 78 geolocation light loggers were deployed on adult Antarctic fur seals at three sub-Antarctic/Antarctic sites: South Georgia (n=30), Cape Shirreff (n=18) and Marion island (n=30). Blood and whisker samples were collected for each individual at deployment and on return to facilitate analysis of winter prey consumption.

Laboratory activity/analysis:
Currently whisker samples are being readied for isotopic analysis.