Title

Fidelity of dugongs to Dugong Protection Areas and their fine-scale movements within them

Objective

To document the fine-scale habitat use of dugongs in the Dugong Protection Areas (DPA) Zone A and their fidelity to those areas.

Relevance

If the Dugong Protection Areas are to work, the areas will have to support significant numbers of dugongs at all times and management will need to minimise all impacts. This will require knowledge of the fine-scale habitat use of dugongs within these areas and the movement of dugongs within DPA boundaries. At present, such information is available only for the Hinchinbrook and Shoalwater DPA As. Priority should be accorded to the other DPA As in the Great Barrier Reef, especially those in the Townsville and Mackay regions.

Feasibility

James Cook University researchers have documented small and large scale movement patterns of more than 50 dugongs in five areas in Australia using this technique which has also been used successfully for more than 100 manatees in Florida over 10 years.

Methodology

At least five satellite transmitters will be used to track dugongs for up to six months in each of two years and each of two regions: (1) Townsville and (2) Mackay. Dugongs will be caught in each area and fitted with the transmitters which broadcast information to polar-orbiting NOAA satellites. This information will be interpreted and disseminated by Service ARGOS, and information on location (correct to 150 m), dugong activity and water temperature made available via e-mail. Parallel studies in the southern Great Barrier Reef and the Gulf of Carpentaria suggest that an average of two locations will be received from each dugong daily. Tagged dugongs will also be telemetered with time-depth recorders to record dive behaviour. This information will be used to refine correction factors used in the aerial surveys (see Project 4 entitled ‘Improving estimates of absolute abundance of dugongs’).

After six months of tracking the transmitter attachment will self-release from the dugong. Attempts will be made to retrieve the transmitter using the latest satellite derived locations and the VHF beacon in each transmitter. If the instruments are retrieved, they will be re-deployed on additional dugongs after replacement of batteries and down-loading of the dive data. Some instruments may shed prematurely due to failure of the attachment link which is designed to snap if the transmitter becomes fouled in mangroves or coral, or if it is attacked by sharks or crocodiles.

The data on the movements of the tagged dugongs will be compared with the spatial information on other impacts using a Geographic Information System.

Approximate cost

$90 000 per year for two years per area

Time required

Two years per area