Title

Are there seasonal changes in dugong distribution in the southern Great Barrier Reef?

Objective

To determine whether the Dugong Protection Areas support a significant proportion of the dugong population in the southern Great Barrier Reef at all times of the year.

Relevance

The rationale behind the Dugong Protection Areas is that they support a significant proportion of the dugongs in the southern Great Barrier Reef throughout the year. This conclusion was based on the analysis of all available distribution data by Preen and Morissette (1997). However, most of the regional scale surveys have been timed to take advantage of the calm weather after the south-east trades finish and before the wet season. The importance of the Dugong Protection Areas as year-round sanctuaries for dugongs needs to be verified.

Feasibility

Methods to estimate the distribution and abundance of dugongs at regional scales using aerial survey have been developed by researchers at James Cook University and extensively applied in Australia and overseas. Although the methodology to do this is well established, this approach is expensive (e.g. $80 000 for the area Hervey Bay to Cape Bedford) and it may be difficult to find the necessary weather window in winter months. However, it would probably be possible in June–July using two aircraft and two survey crews. Ideally, it should be done in the same year as the regular regional survey timed for November 1999 (i.e. either or both July 1999 and July 2000). This approach will still provide only one or two snapshots of the winter distribution of dugongs in the southern Great Barrier Reef and would need to be replicated.

This approach is likely to be spatially less comprehensive than the winter surveys proposed above because there are no winter regional scales surveys except some qualitative shoreline surveys conducted by Heinsohn in the 1970s. However, it is far more temporally comprehensive than one or two winter regional surveys and has the advantage of using data for a variety of sources. There are several series of local scale surveys conducted at intervals of weeks/months for the Shoalwater Bay region and the Townsville–Hinchinbrook region as well as information from satellite-tracked dugongs.

Methodology

There are two approaches to answering this question:

1. To repeat the regional scale surveys at different times of the year.
2. To conduct a desktop study of all available information on dugong distribution in the southern Great Barrier Reef (aerial survey and satellite tracking) to determine if there is any evidence for seasonal trends in distribution or movements.

Approximate cost

1. Winter surveys

   July 1999 $80 000

   July 2000 $80 000

2. Desktop study

$5000 (could be done in conjunction with study of relationship between fine-scale habitat use and impacts).

Time required

1. Winter surveys: one month survey time, six months to final report
2. Desk top study: one month