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. 2020 Oct 19;10(1):17710.
doi: 10.1038/s41598-020-73579-y.

Environmental influences on foraging effort, success and efficiency in female Australian fur seals

Cassie N Speakman  1 , Andrew J Hoskins  2 , Mark A Hindell  3 , Daniel P Costa  4 , Jason R Hartog  5 , Alistair J Hobday  5 , John P Y Arnould  6
Affiliations

Environmental influences on foraging effort, success and efficiency in female Australian fur seals

Cassie N Speakman et al. Sci Rep. .

Erratum in

Abstract

Understanding the factors which influence foraging behaviour and success in marine mammals is crucial to predicting how their populations may respond to environmental change. The Australian fur seal (Arctocephalus pusillus doriferus, AUFS) is a predominantly benthic forager on the shallow continental shelf of Bass Strait, and represents the greatest biomass of marine predators in south-eastern Australia. The south-east Australian region is experiencing rapid oceanic warming, predicted to lead to substantial alterations in prey diversity, distribution and abundance. In the present study, foraging effort and indices of foraging success and efficiency were investigated in 138 adult female AUFS (970 foraging trips) during the winters of 1998-2019. Large scale climate conditions had a strong influence on foraging effort, foraging success and efficiency. Foraging effort and foraging success were also strongly influenced by winter chlorophyll-a concentrations and sea-surface height anomalies in Bass Strait. The results suggest increasing foraging effort and decreasing foraging success and efficiency under anticipated environmental conditions, which may have population-level impacts.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
Location of the Kanowna Island breeding colony (♦) within south-eastern Australia and inflow of major water bodies (SAC—South Australian Current; SASW—Sub-Antartic Surface Waters; EAC—East Australian Current) into Bass Strait. Arrows represent current flow and dashed lines represent water flow into Bass Strait. The Bonney Upwelling region is indicated by the shaded grey area and extends into South Australia. Inset map shows the position of the region relative to Australia. The shaded box indicates the region for which local-scale environmental conditions were derived. Map generated using marmap (version 1.0.3), oce (version 1.1-1) and ocedata (version 0.1.5) packages in the R statistical environment (version 3.6.1), and modified using Adobe Illustrator version 23.0.3.
Figure 2
Figure 2
Predicted response from Generalised Additive Mixed effects Models of foraging effort of female Australian fur seals to local-scale environmental conditions. Models were constrcuted using the mcgv package version 1.8.31– in the R statsitical environment version 3.6.1.
Figure 3
Figure 3
Relationships between foraging effort of female Australian fur seals and local-scale environmental conditions identified using Linear Mixed Effects models. Models were constrcuted using the nlme package version 3.1-140 in the R statsitical environment version 3.6.1.
Figure 4
Figure 4
Predicted response from Generalised Additive Mixed effects Models of foraging effort of female Australian fur seals to large-scale climate indices. Models were constrcuted using the mcgv package version 1.8.31– in the R statsitical environment version 3.6.1.
Figure 5
Figure 5
Relationships between foraging effort of female Australian fur seals and large-scale climate indices identified using Linear Mixed Effects models. Models were constrcuted using the nlme package version 3.1-140 in the R statsitical environment version 3.6.1.
Figure 6
Figure 6
Relationships between the benthic Foraging Trip Success Index and Foraging Trip Efficiency Index of female Australian fur seals with local-scale environmental conditions and large-scale climate indices identified using Linear Mixed Effects models. Models were constrcuted using the nlme package version 3.1-140 in the R statsitical environment version 3.6.1.
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