Significance of the Gnaraloo Bay Rookery

A rookery with 300 turtle nests per season is considered to be a significant turtle breeding area.  The number of nests per breeding season in the Gnaraloo Bay Rookery has been 426 (2010/11), 522 (2009/10) and 368 (2008/09) within a 7km stretch of beach. As such the area is considered to be a significant sea turtle rookery, particularly for Loggerheads (Caretta caretta).

During March 2011, Gnaraloo released its data sets to a Department of Environment and Conservation (DEC) researcher in Shark Bay for input and use in estimates of Loggerhead population numbers in WA.  The researcher advised that Dirk Hartog Island at Shark Bay has the biggest Loggerhead rookery in Western Australia (WA), while Bungelup at Cape Range National Park and Gnaraloo Bay have the highest Loggerheads nesting on the mainland. Linda Reinhold, Project Eden ecologist & Shark Bay representative of the State Marine Turtle Recovery Team, DEC, March 2011:

‘Seasons like 2010/11 resulted in most of the main nesting beach at Dirk Hartog Island being unexpectedly washed away which reinforces the importance of viewing all breeding beaches together to sustain the population.  Dirk Hartog is not necessarily secure as a unit by itself and active conservation at significant mainland rookeries like Gnaraloo Bay is important for the Loggerhead population as a whole … The Gnaraloo Bay turtles are recognised as part of the third largest Loggerhead turtle population in the world and probably the best vantage point along the population’s range to record the parameters of their breeding biology.  This is because Gnaraloo is on the mainland, has accommodation facilities, and the relative density of Loggerhead nests means that enough data can be gathered to be statistically meaningful’.

James Cook University (Queensland) advised during February 2010 that there are few long term data sets for sea turtles in WA, in particular for Loggerheads.  While most of the Loggerhead turtle nesting sites in WA are offshore and remote, the Gnaraloo mainland rookery provides an excellent opportunity for the collection of robust long term monitoring data.

The CSIRO has used GTCP data sets for ecosystem modelling work for the Ningaloo – Exmouth region that is attempting to capture system function and give insight into sustainable development and natural resource management.  Dr. Fulton, Marine and Atmospheric Research, CSIRO Tasmania, February 2010:

‘… turtles and their survivorship is a particularly important objective for the region, but one that is highly uncertain … The size of the Gnaraloo Bay Rookery means that it is likely to make a substantial contribution to the Loggerhead turtle population. Gnaraloo’s geographic location is in an area where there is no information available on the turtles and related system components. Together this makes the monitoring work in the Gnaraloo Bay Rookery a key source of information that could help reduce uncertainty about the functioning of the system and conservation management’.

These considerations make it obvious that it is important that monitoring work continues under the seasonal Gnaraloo Turtle Conservation Program.

Cheers, Karen