Marsh et. al., 2005:

"Recent studies have estimated the historical abundance of large marine vertebrates to determine potential targets for conservation. This approach was validated using 1990s aerial survey estimates of dugong abundance and an estimate of the decline in dugong numbers since the 1960s based on changes in the catch per unit effort of dugong by-catch in a government shark control program on the east coast of Queensland, Australia. This analysis indicated that the catch rate of dugongs caught in shark nets, at six locations between latitudes 16.58°S and 28.8°S, declined at an average of 8.7 per cent per year between 1962 and 1999. This represents a decline to 3.1 per cent of initial catch rates over the sampling period. If the changes in the populations sampled by the shark nets and aerial surveys were equivalent, this result suggests that the region supported 72 000 dugongs in the early 1960s compared with an estimated 4220 dugongs in the mid-1990s."

Fig 2.  Profile of the annual estimated mean numbers of dugongs caught for the period 1962 - 1999 for the balanced data set from six shark-netting contract areas, showing a strong overall decline in the number of dugongs caught per month per beach.  The profile was estimated by bootstrapped fits of log-linear models with linear and quadratic terms in year for each beach.  The bootstrap samples were generated by stratifying on beach within area; thus, for any sample, a beach was either completely included or excluded.  The confidence bands have 95% pointwise coverage.  The estimated rate of decline averages 8.7%/yr.

 

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Citation and/or URL

Marsh, H., De'ath, G., Gribble, N., and Lane, B. 2005, Historical marine population estimates:  Triggers or targets for conservation?  the dugong case study, Ecological  Applications, 15(2) pp. 481-492.

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Spatial Coverage

 Cairns to the Gold Coast

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Temporal Coverage

 1962 - 1999

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Update Frequency

 Not applicable 

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Other Information

Heinsohn, G (1972)  A Study of Dugongs (Dugong dugon) in Northern Queensland, Australia. Biol. Cons. 4(3): 205-213.

Marsh, H.,  De'ath, G., Gribble, N & Lane, B (2001) 'Shark Control Records Hidncast Serious Decline in Dugong Numbers off the Urban Coast of Queensland', GBRMPA Research Publication No. 70, Townsville, Queensland.