Limpus et al., 2003:

"There has been significant downward trend in the mean carapace length (CCL) of the nesting female C. mydas at Raine Island and Moulter Cay during mid summer over 26 breeding seasons, 1976-2001 (Limpus et al. 2003). While there was no significant change in CCL of the untagged females recorded at these islands during the 17 year period, 1985-2001, the size of the “older” turtles with a past breeding history has deceased significantly during the same period. This decrease in the size of the females has occurred in conjunction with a progressive increase in remigration interval. While the long term census of the size of the annual nesting population has not provided a clear indication of the stability of this C. mydas stock, the changes in CCL and remigration interval are consistent with a population that could be in the early stages of population decline as a result of excessive loss of adult females (Limpus et al. 2003).

Within a few years of commencement of our tagging at Raine Island it became apparent that many of the turtles were migrating from feeding areas outside of Australia.  In addition, large numbers of C.mydas were being hunted for food, both at the village level and for commercial market, within the feeding areas supplying turtles to the Australian rookeries.  So, while there has been almost total protection of the nesting females at the GBR rookeries for many years, the population is under a large but imprecisely determined harvest pressure.  In many areas this harvest targets large females but in Torres Strait gravid females migrating to breed are preferred where they are available.  The pattern that has developed this century with turtle harvests in other countries is that marine turtle population numbers will crash following several decades of intense harvesting.  Given that the large harvests that target the Raine Island turtles have only been operating in the past 2 or 3 decades, concern must be held for the future stability of this population.

There has been a progressive decline in the size of nesting females over the decades of the study.  This decline was associated with a decline in size of remigrant turtles.  There was no decline in the size of turtles being tagged for the first time.  The decrease in size of the females occurred in conjunction with a progressive increase in remigration interval.  In recent times, the nesting population is also characterised by a very low recruitment rate.  These demographic characteristics may indicate that this large population is in the early stages of decline as a result of loss of adult turtles." 

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Citation and/or URL

Limpus, C.J., Miller, J.D., Parmenter, C.J., and Limpus, D.J., 2003,  The green turtle, Chelonia mydas, population of Raine Island and the Northern Great Barrier Reef: 1843-2001,  Memoirs of the Queensland Museum, 49(1); 349-440.

Spatial Coverage

Northern Great Barrier Reef

Temporal Coverage

1843 to 2001

Update Frequency

Not applicable 

Other Information

None