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Historical dynamics of the fur seal population : evidence of regulation by man?

Arnould, John, Boyd, I.L. and Warneke, R.M. 2003, Historical dynamics of the fur seal population : evidence of regulation by man?, Canadian journal of zoology, vol. 81, no. 8, pp. 1428-1436.

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Title Historical dynamics of the fur seal population : evidence of regulation by man?
Author(s) Arnould, John
Boyd, I.L.
Warneke, R.M.
Journal name Canadian journal of zoology
Volume number 81
Issue number 8
Start page 1428
End page 1436
Publisher NRC Research Press
Place of publication Ottawa, Ont.
Publication date 2003-08
ISSN 0008-4301
1480-3283
Keyword(s) seals (Animals)
animal populations
Summary The Australian fur seal (Arctocephalus pusillus doriferus) was severely over-exploited in the 18th and 19th centuries and until relatively recently its population had remained steady at well below estimated presealing levels. However, the population is now increasing rapidly (6%–20% per annum) throughout its range and there is a need to understand its dynamics in order to assess the potential extent and impact of interactions with fisheries. Age distribution (n = 156) and pregnancy rate (n = 110) were determined for adult females collected at a breeding colony on Seal Rocks, southeast Australia, in 1971–1972. Mean ± SE and maximum observed ages were 9.37 ± 0.41 and 20 years (n = 1), respectively. A stochastic modelling approach was used to fit an age distribution to the observed age-structure data and calculate rates of recruitment and adult survival. Annual adult female survival and recruitment rates between 1954 and 1971 were 0.478 ± 0.029 (mean ± SE) and 0.121 ± 0.007, respectively, suggesting that the population was experiencing a decline during the 1960s. The pregnancy rate increased from 78% at 3 years of age to an average of 85% between 4–13 years of age before significantly decreasing in older females (the oldest was 19 years of age). There was no significant effect of body mass or condition on the probability of a female being pregnant (P > 0.5 in both cases) and the nutritional burden of lactation did not appear to affect pregnancy rates or gestational performance. These findings suggest that the low survivorship was due to density-independent effects such as mortality resulting from interactions with fishers, which are known to have been common at the time. The recent increase in the population is consistent with anecdotal evidence that such interactions have decreased as fishing practices have changed.
Language eng
Field of Research 060801 Animal Behaviour
HERDC Research category C1.1 Refereed article in a scholarly journal
Copyright notice ©2003, NRC Canada
Persistent URL http://hdl.handle.net/10536/DRO/DU:30015945

Document type: Journal Article
Collections: School of Life and Environmental Sciences
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Every reasonable effort has been made to ensure that permission has been obtained for items included in DRO. If you believe that your rights have been infringed by this repository, please contact drosupport@deakin.edu.au.