Unsustainable harvest of dugongs in Torres Strait and Cape York (Australia) waters: two case studies using population viability analysis

Authors

  • Robert Heinsohn,

    Corresponding author
    1. Centre for Resource and Environmental Studies, Australian National University, Canberra A.C.T. 0200 Australia
      *All correspondence to: Robert Heinsohn. Tel: 61-2-6125 2100; Fax: 61-2-6125 0757; Robert.Heinsohn@anu.edu.au
    Search for more papers by this author
  • Robert C. Lacy,

    1. Department of Conservation Biology, Daniel F. and Ada L. Rice Center, Chicago Zoological Society, Brookfield, IL 60513, USA
    Search for more papers by this author
  • David B. Lindenmayer,

    1. Centre for Resource and Environmental Studies, Australian National University, Canberra A.C.T. 0200 Australia
    Search for more papers by this author
  • Helene Marsh,

    1. School of Tropical Environment Studies and Geography, James Cook University, Douglas, Townsville, 4811and CRC Torres Strait, P.O.Box 772, Townsville 4801, Australia
    Search for more papers by this author
  • Donna Kwan,

    1. School of Tropical Environment Studies and Geography, James Cook University, Douglas, Townsville, 4811and CRC Torres Strait, P.O.Box 772, Townsville 4801, Australia
    Search for more papers by this author
  • Ivan R. Lawler

    1. School of Tropical Environment Studies and Geography, James Cook University, Douglas, Townsville, 4811and CRC Torres Strait, P.O.Box 772, Townsville 4801, Australia
    Search for more papers by this author

*All correspondence to: Robert Heinsohn. Tel: 61-2-6125 2100; Fax: 61-2-6125 0757; Robert.Heinsohn@anu.edu.au

Abstract

A significant proportion of the world's remaining dugongs (Dugong dugon) occur off northern Australia where they face various anthropogenic impacts. Here, we investigate the viability of two dugong meta-populations under varying regimes of indigenous hunting. We construct population viability analyses (PVAs) using the computer package VORTEX and published estimates of population sizes and hunting rates. In Torres Strait between Cape York and New Guinea, our models predict severe and imminent reductions in dugong numbers. Our ‘optimistic’ and ‘pessimistic’ models suggest median times for quasi-extinction of 123 and 42 years, respectively. Extinction probabilities are also high for eastern Cape York Peninsula. We demonstrate the inadequacy of reserves when harvest rates in neighbouring areas are high, identify the maximum harvest rates for meta-population stability and emphasise the urgent need for indigenous community involvement in management to establish sustainable rates of dugong harvest in these regions.

Ancillary