WEST KIMBERLEY PLACE REPORT - Department of Sustainability ...

visit the bay each year.
The Roebuck Bay mudflat system is best known because it is one of the most
significant sites for international migratory waders on the Australian continent, and its
protection under the Ramsar Convention confirms that status. While each migratory
species' population follows its own particular annual migration path, there are
nonetheless generalised global migration routes that connect breeding areas in the
north, via stopovers in temperate and subtropical zones, to non-breeding areas in the
south. These routes are called flyways. The East Asia–Australasian Flyway, of which
Roebuck Bay is part, is one of eight major migratory waterbird flyways around the
world. From August each year, at the end of the northern summer, shorebirds make a
journey across oceans and continents to reach Roebuck Bay, sometimes flying for
stretches of up to 8,000 kilometres without landing.
Roebuck Bay has been known to hold as many as 170,000 birds at one time (Rogers
et al. 2003). Sixty four waterbird species have been recorded here, and 34 of these are
listed under international conservation treaties. The site supports more than one
percent of the national population for 21 species of wader, including pied
oystercatchers (Haematopus longirostris), Mongolian plovers (Charadrius mongolus)
and ruddy turnstones (Arenaria interpres). Australian shorebirds also make Roebuck
Bay home for part of the year, and for many it is their main breeding ground. Redcapped
plovers (Charadrius ruficapillus) and black-winged stilts (Himantopus
himantopus) occur in large numbers; more than one per cent of their flyway
populations may spend time at Roebuck Bay each year. Twenty-two of the 24
Australian raptor species also live around the shores of Roebuck Bay (Rogers et al.
2003).
While the mudflats are spectacular at the height of the wet season, the best time for
birds is at the end of the wet, when the ground starts to dry out. As surface water is
absorbed and evaporated, mud is exposed and a rich feast begins. Birds feed on the
multitude of invertebrate fauna, which have reproduced rapidly during the wet
(Rogers et al. 2003). Because little rain falls during the dry season, for much of the
year surface water at the mudflats is restricted to a few permanent or semi-permanent
waterholes and streams. Most of these are not supplied directly by rainfall, but are
maintained by water seeping from underground aquifers – these in turn are
replenished each wet season, when the whole area is once more immersed.
The rivers of the Kimberley: a haven for fish
Researchers have found that a number of fish species in the northern and western
rivers and in the Fitzroy system are endemic and have distributions restricted to the
Kimberley. This is thought to be the result of a number of factors: the varied habitats
throughout the river systems, including areas of extremely rugged topography in the
upper catchment; the periodic very high flows which occur, and the large area covered
by the Fitzroy catchment (Morgan et al. 2002). Recent surveys recorded 37 species of
fish in the northern and western rivers, including 23 freshwater species and 14
estuarine or marine species. Three of the freshwater species did not have scientific
names at the time of the survey, but researchers recorded names of fish, where
available, in Bunuba, Gooniyandi, Ngarinyin, Nyikina and Walmajarri. The
researchers found that the range of fish species varied significantly between the lower,
middle, and upper reaches of each river, and was different again in billabongs, smaller
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