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Presented at the NABS Annual meeting, Vancouver, British Columbia, 2004
in Disturbance Ecology 1
Will exotic crayfish undermine restoration of a southwestern stream?
K.J. Adams, G. Meraz, G.A. Haden, and J.C. Marks. Department of Biology, Northern Arizona University, Flagstaff, Arizona, USA
Crayfish (Orconectes virilis) are invading Fossil Creek, Arizona, which is scheduled for flow restoration and exotic fish removal by 2005. We combined crayfish surveys, food consumption and preference experiments, with stable isotope analysis to predict how crayfish will respond to restoration. Surveys showed that crayfish are most abundant at downstream sites, with densities decreasing at upstream sites. Crayfish have not yet invaded sites farthest upstream above the hydropower dam. Surveys also indicated a bias towards sampling larger individuals. Crayfish from the stream consumed algae, detritus, aquatic insects, snails and fish eggs, but prefered macroinvertebrates over algae and detritus when both were available. Stable isotope values for crayfish confirmed that their diets are a mixture of macroinvertebrates, algae, and detritus. Stable isotope analysis also indicated that exotic fish may be controlling crayfish by competition or predation. We predict that removing exotic fish with a piscicide will increase crayfish by releasing them from predation and competition, confounding efforts to restore the natural trophic structure of the stream. We recommend that removal of all sizes of crayfish be included in restoration plans for Fossil Creek.
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