Meeting Abstract

64.1  Sunday, Jan. 6  Native Fish Populations Increase Following Flow Restoration and Exotic Fish Removal in Fossil Creek, Arizona O’NEILL, M. W.*; PACE, C. M.; HADEN, G. A.; MARKS, J. C.; Northern Arizona University; NAU; NAU; NAU mwo@nau.edu

The decommissioning of the Fossil Creek dam in Arizona presents a unique opportunity to study the effects of flow restoration and exotic fishes removal (bass and sunfish) on five species of native fishes. Here we use snorkel surveys and stable isotopes to compare the responses of native fish across four treatments: 1) control sites above the dam which have always experienced full flow and only native species, 2) sites where only flow was restored which never had exotic fish, 3) sites where flow was restored and exotic fish remain, 4) sites where flow was restored and exotic fish were removed. Native fish populations increased at all sites without exotic fish, including control sites. However, increases were significantly higher in the treatment where exotics were removed and flow was restored relative to all other treatments. Native fish increased 10-fold at these sites, with the smallest sized fishes responding greatest. The only sites where natives did not increase were where exotics are still present regardless of flow restoration. Isotope data suggest that chub may be returning to their role as top predator. We conclude that restoring flow alone does not increase native fish populations. However, restoring flow and removing exotic fish does help native fish populations and may be an important management tool for reviving native fish populations in the Southwest.