Interactions of exotic crayfish and native and exotic fish and invertebrates

Despite progress towards understanding exotic crayfish it remains difficult to predict the degree to which they will affect native ecosystems.  For example, in the southwestern United States crayfish dominate some streams but maintain low densities in other nearby streams.  Many of these streams have complex fish faunas comprised of both native and exotic fish some of which have overlapping home ranges with crayfish.   This research experimentally studies the interactions of exotic crayfish with the biological community that they are invading, comprised of both native and exotic species. The first experiment compared the vulnerability of crayfish to native and exotic predators.  In enclosures, young of the year crayfish were exposed to native chub and exotic bass to test if native predators can serve as a similar biological control as predatory bass.   Results showed that there was a greater percent survivorship of crayfish in enclosures with native chub compared to enclosures with bass, although this result was not statistically significant.  The second experiment tested how invasive crayfish affect aquatic insect emergence using large leaf litter enclosures with emergence traps with and without crayfish.  The presence of crayfish decreased emergence showing that crayfish effects can extend into the terrestrial environment.