The Rise and Fall of Fossil Creek, a Southwestern Desert Oasis

Fossil Creek is a spring-fed travertine stream in central Arizona that since 1909 was utilized for hydropower generation that severely depleted flows; it was occupied by a suite of six native fish species (four minnows and two suckers) plus introduced green sunfish, smallmouth bass, and others.  After a decade of planning and compliance, in 2004-2005 the power facility was decommissioned, a fish barrier was emplaced, Fossil Creek flows were restored, and the stream was chemically-treated to eliminate non-native fishes, after which we bi-annually (spring and autumn) monitored post-project recovery of the fish community.  Monitoring from 2005 to 2011 indicated the historical native fish fauna was intact upstream from the fish barrier.  All species, longfin dace, headwater chub, roundtail chub, speckled dace, Sonora sucker, and desert sucker are reproducing, recruiting, and represented by multiple age/size classes.  Total numbers and relative abundances varied spatially and temporally and were subject to wide fluctuation.  Hoop net and minnow trap CPE of total fish and the most abundant taxa, headwater+roundtail chub and specked dace, increased during the two years following stocking of salvaged individuals, but declined and apparently stabilized thereafter.  Dispersal varied among species but all eventually re-occupied the treatment reach.  Widespread publicity associated with the restoration drew large numbers of visitors who overwhelmed limited infrastructure, and some of whom misused and damaged area resources, requiring restrictions.  A native (chub) sport fishery was established soon after restoration but is little-used.  Non-native smallmouth bass exceeded the fish barrier after compromise in 2011 and again threaten the native fish community.  Actions to again remove the non-native bass have been hampered by political efforts within Arizona to restrict or limit the use of piscicides through the passage of legislation.