Oral Presentation Australian Freshwater Sciences Society Conference 2018

Distribution and habitat associations of native and introduced crayfish in urban wetlands. (#91)

Holly E. Emery-Butcher 1 , Stephen Beatty 1 , Belinda J. Robson 1
  1. Murdoch University, Murdoch, WA, Australia

Both native (Cherax cainii, Cherax preissii koonac, Cherax quinquecarinatus gilgie) and invasive crayfish (Cherax destructor yabby) occur in urban wetlands on the Swan Coastal Plain (SCP), yet little is known of their distribution in relation to wetland characteristics. Aside from numerous natural, mostly seasonal wetlands, the SCP contains hundreds of mostly perennial, anthropogenic wetlands. This project aimed to: identify habitat characteristics associated with the presence of introduced and native freshwater crayfish in SCP wetlands; compare distributions of introduced and native crayfish in natural and anthropogenic urban wetlands. Adult crayfish were captured using baited box traps set overnight in 30 anthropogenic and 23 natural wetlands. Sweep samples were used to capture juvenile crayfish. Habitat characteristics and water quality variables were quantified. Log-linear modelling, ordination, ANOSIM and BIO-ENV were used to analyse results. All four crayfish species were captured, although invasive C. destructor dominated samples. Few C. cainii or Koonacs were collected; the latter was only present in newly-developed suburbs. There was evidence of recruitment in both yabby and gilgie populations. Yabby occurrence was positively related to ease of accessibility to wetlands by humans, presence of fringing vegetation and presence of adjacent waterbodies. Native crayfish presence was positively associated with natural wetlands, probably because these populations are remnants of pre-development populations. Within-wetland factors affecting crayfish presence included a natural substratum type, absence of flow and perennial water regime. Habitat characteristics did not predict invasive crayfish presence, but accessibility of wetlands to humans may encourage translocations. Native crayfish may be less likely to be translocated than yabbies, a desirable species for human consumption. Gilgies did co-occur with yabbies and also occurred in both anthropogenic and natural wetlands. The presence of yabbies may be limiting the distribution of native crayfish in urban SCP wetlands.