Doupe el al .: Introduction of a tropical 'yabby' to Lake Kununurra 
on redclaw crayfish, although we only caught four 
individuals because very few barramundi are found 
in Lake Kununurra as a consequence of damming 
(Doupe & Bird 1999). 
Lesser salmon catfish and silver cobbler were collected 
at nine sites in Lake Kununurra and six sites in Lake 
Argyle, and redclaw crayfish were detected only in 
samples taken from these two species in the lagoons of 
Emu Creek and Four Mile Creek (see Fig 1). No evidence 
of redclaw was found in gut examinations of 94 lesser 
salmon catfish and 20 barramundi sampled outside of 
Lake Kununurra; we are therefore uncertain of the 
distribution of redclaw crayfish in either Lake Kununurra 
or the greater Ord River system, however we are aware 
of redclaw crayfish being caught at the lower end of Lake 
Kununurra (A. Storey, UWA, pers comm.; R.Doupe 
unpub data). 
What are the likely impacts of introducing a crayfish 
to a water body where the resident community has 
(presumably) evolved in their absence (sensu Horwitz 
1990; Jasinska et al 1993; Horwitz & Knott 1995; Lynas el 
al 2004)? Lamentably we are presently unable to answer 
this question for Lake Kununurra, however we have a 
number of concerns. For example, in southwestern 
Australia, introduced Cherax have shown aggressive and 
predatory behaviour toward congenerics (see Austin & 
Ryan 2002; Molony et al 2002) and aquatic vertebrates 
(Bradsell et al 2002), and Fernendez & Rosen (1996) 
documented similar antagonistic behaviour toward 
aquatic reptiles by introduced virile crayfish Orconectes 
virilis (Hagen). Jones & Ruscoe (2001) have described 
redclaw crayfish as "gregarious" in a crowded 
monoculture, but what might we anticipate when Lake 
Kununurra suddenly has an extra decapod? In North 
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