Preliminary assessment of freshwater crayfish as environmental indicators of human impacts in canyons of the blue Mountains, Australia

Canyoning has become a popular recreation activity in the Greater Blue Mountains World Heritage Area (Australia), and park management consider that the activity is having an impact on the local fauna of the fragile canyon ecosystems. Although only limited data exist on the native freshwater crayfish populations that inhabit these canyons, it has been suggested that freshwater crayfish have the potential to act as a rapid bioindicator of human impacts. As a preliminary assessment, we sampled crayfish from two canyons that received high visitation and two with low visitation. We recorded only a single species, Euastacus spinifer and this was found to occur at higher altitudes than previously recorded. There was no significant difference in crayfish abundance or size between visitation levels. There were, however, differences in crayfish abundance between individual canyons. Animals within a canyon had the same colour morph which we deduced to be genetic under selection pressure. We conclude that with an appropriate baseline dataset, crayfish could potentially provide a rapid assessment method for use by canyoners and other non-specialists to underpin management decisions.