Abstract

In the south-west of Australia, interspecific interactions between non-native yabbies (Cherax albidus) and indigenous marron (Cherax tenuimanus) are not well understood. While there is abundant evidence to suggest that invasive freshwater crayfish are detrimental to native species, it appears that in some waterbodies, where displacement has been documented, marron populations are expanding in the presence of well-established yabby populations. This study investigated the influence of crayfish gender, relative size, life-stage and prior residence on shelter acquisition between marron and yabbies. Individual crayfish were placed into an aquarium containing a single shelter. After 24h tanks containing a marron received a yabby, and tanks containing a yabby received a marron. The shelter occupant and any confrontation between crayfish were recorded after 10 minutes, and then every 4h for a 24h period. Intruding crayfish included same or opposite sex heterospecifics that were the same size or larger than the resident crayfish. One treatment included berried yabbies as the resident or intruder, testing the assertion that this life stage is the most successful at acquiring shelter and maintaining residence. As prior residents, marron occupied the shelter more frequently than intruding yabbies (c2(1) = 4.455, P = 0.035), and larger marron used the shelter more often than smaller marron (c2(1) = 9.966, P = 0.002). It is possible that the smaller body-size of yabbies (compared to marron) may be the major factor limiting population expansion in the presence of marron, especially in waterbodies where shelter is a limited resource. Results of this study provide preliminary information on interspecific interactions between marron and yabbies in Western Australia.

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