Abstract

Yabbies are widespread throughout the wheatbelt region in Western Australia. Although there are no reports of farm dams being damaged by yabby burrows, export markets have expressed concern at the potential damage to reservoirs, irrigation channels or pond banks that may be caused by burrowing crayfish. Techniques for casting and excavating the casts of burrows were evaluated. Expanding polyurethane foam was better than concrete, plaster or resin as it was lighter, less brittle and gave a three dimensional representation of the burrow. Excavating the casts of burrows using high-pressure water was better than digging as it was more efficient and preserved the shape of the casts. The maximum (65 cm) and average (26 cm) burrow lengths were less than in anecdotal reports, and less than those reported for other burrowing crayfish species. This is probably the reason why the physical integrity of the walls in any of the dams visited (n=25) was not compromised by yabby burrows. The occurrence of yabby burrows increased from 25% of dams in spring 1999 to 70% in autumn 2000. There was no relationship between burrow occurrence and either sediment type or water chemistry. The majority of burrows had only one entrance to a simple tunnel leading to a terminal cavern. Channels and large dams had longer burrows than small dams. Burrows in the levees of channels and dams were more complex than pond bottom burrows. Complex burrows were more prevalent in water bodies where there was a seasonal change in water table height. In 100 m² research ponds, burrowing activity was greater in those with either females only or well-fed yabbies. There was no relationship between the density of yabbies and the number of burrows per unit area.

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