Strip-transect aerial surveys of Shark Bay, Ningaloo Reef and Exmouth Gulf
were conducted during the winters of 1989 and 1994. These surveys were
designed primarily to estimate the abundance and distribution of dugongs,
although they also allowed sea turtles and dolphins, and, to a lesser extent,
whales, manta rays and whale sharks to be surveyed. Shark Bay contains a large
population of dugongs that is of international significance. Estimates of
approximately 10000 dugongs resulted from both surveys. The density of dugongs
is the highest recorded in Australia and the Middle East, where these surveys
have been conducted. Exmouth Gulf and Ningaloo Reef are also important dugong
habitats, each supporting in the order of 1000 dugongs. The estimated number
of turtles in Shark Bay is comparable to the number in Exmouth Gulf plus
Ningaloo Reef (7000–9000). The density of turtles in Ningaloo Reef and,
to a lesser extent, Exmouth Gulf is exceptionally high compared with most
other areas that have been surveyed by the same technique. Shark Bay supports
a substantial population of bottlenose dolphins (2000–3000 minimum
estimate). Exmouth Gulf and Ningaloo Reef were not significant habitats for
dolphins during the winter surveys. Substantial numbers of whales (primarily
humpbacks) and manta rays occur in northern and western Shark Bay in winter.
Ningaloo Reef is an important area for whale sharks and manta rays in autumn
and winter.
The Shark Bay Marine Park excludes much of the winter habitats of the large
vertebrate fauna of Shark Bay. In 1989 and 1994, more than half of all the
dugongs were seen outside the Marine Park (57·4 and
50·7%, respectively). Approximately one-third to one-half of
turtles and dolphins were seen outside the Marine Park (in 1989 and 1994
respectively: turtles, 43 and 27%; dolphins, 47 and 32%). Almost
all the whales and most of the manta rays were seen outside the Marine Park.
Expansion of the Shark Bay Marine Park, to bring it into alignment with the
marine section of the Shark Bay World Heritage Area, would facilitate the
appropriate management of these populations. This would also simplify the
State– Commonwealth collaboration necessary to meet the obligations of
World Heritage listing. The coastal waters of Western Australia north of the
surveyed area (over 6000 km of coastline) are relatively poorly known and
surveys of their marine megafauna are required for wise planning and
management.
Abundance, survival and temporary emigration of bottlenose dolphins (Tursiops sp.) off Useless Loop in the western gulf of Shark Bay, Western Australia
