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Foraging ecology of fur seals at Iles Kerguelen

Entry ID: AADC-02128

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Summary

Abstract: Public summary for project 2128:

The aim of this study is to relate the foraging behaviour of Antarctic fur seals breeding on the Kerguelen Plateau at Iles Kerguelen and Heard Island, to the distribution of prey species at sea. Specifically this project seeks to examine the relationship between predators and prey, and how their locations at sea vary according to the position of major productive ... zones, such as the Antarctic Polar Frontal Zone. This project will provide important data on the relationship between predators and their prey and the developing commercial fisheries in the region. These data are central to improved conservation and management of marine resources on the Kerguelen Plateau.

Variations made to the work plan
The original comparative aspects of the program planned for the 1999/00 season, where fur seals from Iles Kerguelen and Heard Island were to be satellite tracked simultaneously could not be undertaken because of original 1999/00 field season to Heard Island was re-scheduled to 2000/01. Fortunately the project collaborator Dr Christophe Guinet (French CEBC-CNRS) agreed to extend the work program at Iles Kerguelen another season, and the comparative and integrated fur seal-prey-fisheries study over the Kerguelen Plateau was undertaken the following season (2000/01). Details of this study are presented in ASAC project 1251 (CI - Goldsworthy)and 1085 (CI-Robertson).

Significant findings:

The distribution of the foraging activity of Antarctic fur seal females was investigated at Cap Noir (49 degrees 07 S, 70 degrees 45E), Kerguelen Island in February 1998. Eleven females were fitted with a satellite transmitter and Time Depth recorder. The two sets of data were combined to locate spatially the diving activity of the seals. The fish component of the fur seal diet was determined by the occurrence of otolotihs found in 55 scats collected during the study period at the breeding colony. Oceanographic parameters were obtained simultaneously through direct sampling and satellite imagery. The mesopelagic fish community was sampled on 20 stations along four transects where epipelagic trawls were conducted at night at 50 meters of depth. We then investigated, using geographic information systems, the relationship between the spatial distribution of the diving activity of the fur seals and oceanographic factors that included sea surface temperature, surface chlorophyll concentration, prey distribution and bathymetry obtained at the same spatio-temporal scale as the spatial distribution of the diving activity of our study animals. An inverse relationship was found between the main fish species preyed by fur seal and those sampled in trawl nets. However, the diving activity of Antarctic fur seal females was found to be significantly related to oceanographic conditions, fish-prey distribution and to the distance from the colony but these relationships changed with the spatial scale investigated. A probabilistic model of the Kerguelen Plateau was developed that predicted where females should concentrate their foraging activity according to the oceanographic conditions of the year, and the locations of their breeding colonies.

Maternal allocation in growth of the pup was measured in Antarctic fur seals (Arctocephalus gazella) at Iles Kerguelen during the 1997 austral summer. Absolute mass gain of pups following a maternal foraging trip was independent of the sex of the pup but was positively related to the foraging trip duration and to maternal length. However, daily mass gain, i.e. the absolute mass gain of the pup divided by the foraging trip duration, decreased with increasing foraging trip duration but increased with maternal length. While fasting, the daily mass loss of the pup was related to the sex of the pup and initial body mass, with both heavier pups and female pups losing more mass per day than lighter pups and male pups. The mass specific rate of mass loss was significantly higher in female pups than in male pups. Over the study period, the mean growth rate was zero with no difference between female and male pups. The growth rate in mass of the pup was positively related to maternal length but not maternal condition, negatively related to the foraging trip duration of the mother and the initial mass of the pup. This indicated that during the study period heavier pups grew more slowly due to their higher rate of daily mass loss during periods of fasting . Interestingly, for a given maternal length, the mean mass of the pup during the study period was higher for male than for female pups, despite the same rate of daily mass gain. Such differences are likely to result from sex differences in the mass specific rate of mass loss. As female pups lose a greater proportion of their mass per day, a zero growth rate i.e. mass gain only compensates for mass loss, is reached at a lower mass in female pups compared to male pups. Our results indicate that there are no differences in maternal allocation according to the sex of the pup but suggest that both sexes follow a different growth strategy.

Results are in line with the objectives of the project.

Related URL

Link: GET DATA

Description: Download point for the data

Link: VIEW PROJECT HOME PAGE

Description: Public information for ASAC project 2128

Link: VIEW RELATED INFORMATION

Description: Download point for related publications - AAD Only

Link: VIEW RELATED INFORMATION

Description: Citation reference for this metadata record and dataset

Geographic Coverage

(Click for Interactive Map)

Spatial coordinates

N: -47.38

S: -50.95

E: 77.37

W: 64.68

Temporal Coverage

Start Date: 1998-02-06

Stop Date: 2000-03-05

Location Keywords

CONTINENT > ANTARCTICA

GEOGRAPHIC REGION > POLAR

Science Keywords

BIOLOGICAL CLASSIFICATION > ANIMALS/VERTEBRATES

BIOLOGICAL CLASSIFICATION > ANIMALS/VERTEBRATES > MAMMALS

BIOLOGICAL CLASSIFICATION > ANIMALS/VERTEBRATES > MAMMALS > CARNIVORES > SEALS/SEA LIONS/WALRUSES

ISO Topic Category

BIOTA

OCEANS

Platform

SATELLITES

Access Constraints These data are publicly available for download from the provided URL.

Copies of the referenced publications are available to AAD staff.

Use Constraints This data set conforms to the PICCCBY Attribution License
(http://creativecommons.org/licenses/by/3.0/).

Please follow instructions listed in the citation reference provided at http://data.aad.gov.au/aadc/metadata/citation.cfm?entry_id=AADC-02128 when using these data.

Ancillary Keywords

Fur Seals

Tracking

Data Set Progress

COMPLETE

Originating Center

AAD

Data Center

Australian Antarctic Data Centre, Australia

Data Center URL: http://data.aad.gov.au

Data Center Personnel
Name: DATA OFFICER AADC Phone: +61 3 6232 3244 Fax: +61 3 6232 3351 Email: metadata at aad.gov.au Contact Address: Australian Antarctic Division 203 Channel Highway City: Kingston Province or State: Tasmania Postal Code: 7050 Country: Australia

Distribution

Distribution Media: HTTP

Distribution Size: 10 kb

Distribution Format: csv

Fees: Free

Personnel

SIMON GOLDSWORTHY

Role: TECHNICAL CONTACT

Role: INVESTIGATOR

Email: goldsworthy.simon at saugov.sa.gov.au

Province or State: South Australia

Country: Australia

DAVE CONNELL

Role: DIF AUTHOR

Phone: +61 3 6232 3244

Fax: +61 3 6232 3351

Email: dave.connell at aad.gov.au

Contact Address:

Australian Antarctic Division

203 Channel Highway

City: Kingston

Province or State: Tasmania

Postal Code: 7050

Country: Australia

Publications/References

Goldsworthy, S.D., Lea, M-A. and Guinet, C. (2004), Comparison of mass-transfer and isotopic dilution methods for estimating milk intake in Antarctic fur seal pups, Polar Biology, 27, 801-809

Creation and Review Dates

DIF Creation Date: 1999-10-07

Last DIF Revision Date: 2012-07-23

Future DIF Review Date: 1999-10-07

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