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Ecology, management and conservation in natural and modified habitats
RESEARCH ARTICLE

Plausible bounds for maximum rate of increase in magpie geese (Anseranas semipalmata): implications for harvest

Barry W. Brook A B and Peter J. Whitehead A
+ Author Affiliations
- Author Affiliations

A Key Centre for Tropical Wildlife Management, Charles Darwin University, Darwin, NT 0909, Australia.

B Corresponding author. Email: barry.brook@cdu.edu.au.

Wildlife Research 32(5) 465-471 https://doi.org/10.1071/WR02105
Submitted: 11 November 2002  Accepted: 11 February 2004   Published: 8 August 2005

Abstract

We used improved information on fecundity and credible estimates of survival to define the plausible bounds of maximum intrinsic rate of population increase (r m) in magpie geese and explored the management and conservation implications, given current estimates of off-take. We considered previous estimates of r m (0.78, based on time-series analysis of aerial count data) and the corresponding predicted maximum sustainable harvest rates (30–39% per annum) to be excessive, thereby risking poor management decisions. In contrast, our estimate of the maximum plausible range of r m (0.11–0.28) is substantially lower than the previous estimate, and suggests maximum harvest rates of no more than 5–14% of total population size per annum. We consider that it would be unwise to adopt the prior estimate of r m for management policy because it would risk over-exploitation. Our results embody a more precautionary approach to assessing maximum sustainable yield for magpie geese in northern Australia, and are not confounded by migration. The move from a simple empirical model to a partially mechanistic one reflects a significant improvement in understanding, but must nevertheless be viewed as part of an ongoing process of model refinement and testing.


Acknowledgments

We thank Peter Bayliss, David Bowman, Tony Griffiths and an anonymous referee for helpful comments and suggestions, and Keith Saalfeld (Parks & Wildlife Commission NT) for supplying the 2001 recreational harvest data. This work was funded by the ARC Key Centre for Tropical Wildlife Management and the Parks and Wildlife Commission of the Northern Territory.


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