Feral populations of red-claw crayfish (Cherax quadricarinatus) have been identified within the Lake Eyre Basin, the largest internal draining system within Australia and an area of significant ecological and hydrological value. There is concern that the translocated red-claw crayfish is outcompeting the basins’ native crayfish species, the blue-claw crayfish (Cherax destructor). As crayfish are ecosystem engineers, they play a key role in ecosystem functioning and hence, the replacement of a native with an invasive crayfish species can have wider impacts on the basins’ ecological functioning.
The object of this research was to document the extent of the red-claw invasion within the Lake Eyre basin and observe interspecific interactions in related to food-based competition between red-claw and blue-claw. This was accomplished through field surveys and laboratory experiments. Red-claw and blue-claw populations were surveyed at 21 sites within the Lake Eyre Basin, with this data used to produce a map of population overlaps and variances in abundance. Both species were found to co-exist at 3 sites. Where the two species coexisted, red-claw abundance was significantly higher than blue-claw, while blue-claw abundance was higher when in the absence of its competitor.
In the laboratory, both intra-specific and inter-specific interactions were observed through food-based interaction. Preliminary analysis suggests that when the two species are in direct competition for food, the blue-claw is more likely to reach the food resource first and initiate agonistic interactions, however, the red-claw is much more aggressive and ultimately wins the majority of agonistic interactions, taking possession of the food resource. These results have real world consequences as red-claw, being the more aggressive species, has the capacity to displace blue-claw, and alter ecosystem functions. These results are particularly concerning in iconic areas such as the Lake Eyre Basin which have high ecological and cultural values.