Journal of the Royal Society of Western Australia, 87(4), December 2004 
America, the introduction of rusty crayfish Orconectes 
rusticus (Girard), presumably for recreational fishing 
(Horwitz 1990), is believed to be responsible for the 
decline of two endemic conspecifics, O. propinquus 
(Girard) and O. virilis (Hagen)(Lodge et al. 1985). 
Moreover, competitive displacement can occur even 
between endemic conspecifics if the range of one 
expands; in southwestern Australia, the spread of smooth 
marron C. tenuimamis (Smith) has resulted in a rapid 
decline in the population size and distribution of the 
highly restricted hairy marron C. cainii Austin (Austin & 
Ryan 2002). The redclaw crayfish mostly feeds on 
detritus and zooplankton (Loya-Javellana cl al 1993), and 
is able to survive and persist in a wide range of habitats 
(Jones et al. 2000), but what effect will it have on its new 
environment? The extensive burrowing behaviour of the 
introduced 'yabby' C. destructor (or C. albidus)( Clark) 
alters aquatic habitat (Austin 1985) and is thought to 
contribute to the displacement of native crayfish species 
such as smooth marron (Lynas et al 2004). 
Identifiable remnants of redclaw crayfish taken from 
fish guts were sent to P. Mather of the Queensland 
University of Technology for microsatellite gene 
screening, however DNA extraction (see Baker et al 2000) 
was unsuccessful and we were unable to determine the 
genetic origins of those samples. It is important, 
nevertheless, that we understand how these animals are 
entering Lake Kununurra and if they are dispersing 
throughout the Ord River system, because freshwater 
crayfish harbour a wide variety of symbiotic or parasitic 
organisms, including bacteria, fungi and parasitic worms 
(see descriptions in Herbert 1987; Horwitz 1990; Gelder 
1999). Following, if these animals are being translocated 
from wild populations, then what other invertebrates are 
also being introduced? Alternately, if these animals are 
escapees from aquacultures, 'disease-free' status should 
not necessarily diminish concerns for the potential 
introduction of deleterious symbionts, because 
presumably, such a certification is limited a priori in what 
is a 'disease'? Some recent Australian work has 
discovered some disturbing associations between 
cultured redclaw crayfish and the prevalence of 
infectious diseases. For example, rickettsia-like parasites 
have been explicitly linked to a variety of infectious 
diseases in humans and other vertebrates (Romero & 
Jimenez 2002), and these organisms have been found in a 
number of redclaw crayfish aquacultures in Queensland 
where the crayfish is thought to act as an intermediate 
host (Edgerton & Prior 1999). At another Queensland 
redclaw crayfish farm, viral infections characteristic of 
the Parvoviridae have caused mass mortalities and have 
again raised concerns for the potential spread of diseases 
by redclaw crayfish (Bowater et al. 2002). 
We are unaware of any documented accounts in 
Australia of where the introduction of a non-endemic 
tropical crayfish has caused either the displacement or 
elimination of native freshwater species or changes in 
aquatic communities. However, the nature of crayfish 
and particularly their associations with a wide variety of 
organisms, suggests that there are justifiable reasons to 
be concerned with any translocation of them, regulated 
or not. The opportunity to understand better the 
potential impacts of a redclaw crayfish introduction now 
presents itself at Lake Kununurra. 
Acknowledgements: Financial assistance was provided by the Lake 
Kununurra Fish Stock Enhancement Committee and administered by Ord 
Land and Water Inc. We are grateful for the oral histories and 
unpublished data provided by C Astbury, D Harvey, A Storey and T 
Thome, and N Baker and P Mather attempted the genotyping of redclaw 
samples. S Beatty and P Horwitz kindly commented on the draft 
manuscript. 
References 
Anon 1997 The Aquaculture of Non-Endemic Species in Western 
Australia, Redclaw crayfish. Fisheries Management Paper 
No. 100, Department of Fisheries, Perth. 
Austin C M 1985 Introduction of the yabbie, Cherax destructor 
(Decapoda: Parastacidae) into Southwestern Australia. 
Western Australian Naturalist 16:78-82. 
Austin C M 1998 A comparison of clutch and brood size in the 
Redclaw, Cherax quadricarinatus (von Martens) and the yabby, 
C. destructor Clark (Decapoda: Parastacidae). Aquaculture 
167:135-145. 
Austin C M & Ryan S G 2002 Allozyme evidence for a new 
species of freshwater crayfish of the genus Cherax Erichson 
(Decapoda: Parastacidae) from the south-west of Western 
Australia. Invertebrate Systematics 16:357-367. 
Baker N, Byme K, Moore S & Mather P 2000 Characterisation of 
microsatellite loci in the redclaw crayfish, Cherax 
quadricarinatus. Molecular Ecology 9:494. 
Ball J N 1961 On the brown trout of Llyn Tegid. Proceedings of 
the Zoological Society of London 137:599-622. 
Barki A, Levi T, Hulata G & Karplus I 1997 Annual cycle of 
spawning and moulting in the redclaw crayfish, Cherax 
quadricarinatus, under laboratory conditions. Aquaculture 
157:239-249. 
Bowater RO, Wingfield M, Fisk A, Condon K M L, Reid A, Prior 
H & Kulpa E C 2002 A parvo-like virus in cultured redclaw 
crayfish Cherax quadricarinatus from Queensland, Australia. 
Diseases of Aquatic Organisms 50:79-86. 
Bradsell P, Prince J, Kuchling G & Knott B 2002 Aggressive 
interactions between freshwater turtle, Chelodina oblonga , 
hatchlings and freshwater crayfish, Cherax spp.: implications 
for the conservation of the critically endangered western 
swamp turtle, Pseudemydura umbrina. Wildlife Research 
29:295-301. 
Cohen J E 1978 Food Webs and Niche Space. Princeton 
University Press, New Jersey. 
Curtis M C & Jones C M 1995 Overview of redclaw crayfish, 
Cherax quadricarinatus , farming practices in northern 
Australia. Freshwater Crayfish 10:447-455. 
Doupe R G & Bird C 1999 Opportunities for enhancing the 
recreational fishery of Lake Kununurra using barramundi 
luites calcarifer : a review. Proceedings of the Royal Society of 
Queensland 108:41-48. 
Doupe R G & Lymbery A J 1999 Escape of cultured barramundi 
{hates calcarifer Bloch) into impoundments of the Ord River 
system. Western Australia. Journal of the Royal Society of 
Western Australia 82:131-136. 
Doup6 R G & Lymbery A J 2000 Managing translocations of 
aquatic species. Aquaculture Research 31:151-156. 
Doupe R G & Pettit N E 2002 Ecological perspectives on 
regulation and water allocation for the Ord River, Western 
Australia. River Research and Applications 18:307-320. 
Doupe R G, Morgan D L & Gill H S 2005 Prospects for a 
restorative fishery enhancement of Lake Kununurra: a high- 
level tropical impoundment on the Ord River, Western 
Australia. Pacific Conservation Biology 11: in press. 
Edgerton B F & Prior H C 1999 Description of a hepatopancreatic 
rickettsia-like organism in the redclaw crayfish Cherax 
quadricarinatus. Diseases of Aquatic Organisms 36:77-80. 
Elton C 1958 The Ecology of Invasions by Animals and Plants. 
Methuen, London. 
190 
