Marsh et al.,1999:

"The numbers of dugongs caught in shark nets at eight shark contract areas between latitudes 17^o and 28^oS declined from the inception of the Queensland Shark Control Program in 1962. The estimated rate of decline in dugongs caught per beach per year for a balanced data set from the 31 beaches in six localities averaged 8.7% per year [95% CI = (7.1, 10.6)]. This represents a decline to 3.1% (1.4, 6.1) of initial catch rates over the 38-year sampling period (1962–1999). For the full data set from 47 beaches in eight localities, the overall capture rates were 8.2% per year (6.8, 9.7), only marginally lower than for the reduced data set.

This estimated decline in the by-catch of dugongs in shark nets can be taken as an estimate of decline in the dugong populations from all causes averaged over the areas where nets were deployed, provided that: (1) the catch of dugongs was dependent on dugong population density in the contract area, (2) dugongs did not learn to avoid the nets, or (3) dugongs had not been alienated from the contract areas by increased human use of the beaches. Marsh et al. (1999) regard the first two potentially confounding factors as unlikely and have no data to reject or support the third factor. The authors conclude that, at the very least, the netting data suggest a substantial depletion in dugong numbers along the urban coast of Queensland since the early 1960s. This result accords with anecdotal reports by long-term residents including Indigenous peoples of a decline in dugong numbers. If the by-catch of dugongs in shark nets is a reliable index of changes in dugong abundance, our results suggest that by 1999, dugong numbers in the local regions of the shark nets had declined to about 3% of 1960 values, reinforcing concern for the status of the dugong along the urban coast of Queensland based on other evidence."

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Citation and/or URL

Marsh, H., De'ath, G., Gribble, N. & Lane, B. 2001, Shark control records hindcast serious decline in dugong numbers off the urban coast of Queensland, Great Barrier Reef Marine Park Authority, Research Publication 70: 1-24.  

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Spatial Coverage

Urban coast of Queensland 

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Temporal Coverage

1962 - 1999

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Update Frequency

Not applicable 

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Other Information

None