Desert Fishes Council, Tucson, AZ, November 2004.

Patterns of exotic and native fish richness in the Gila River Basin.

P.J. Unmack & W. Fagan

Using the Minckley Sonfishes database, we will examine spatial patterns of native fish decline and exotic fish occurrence within the Gila River Basin. It is generally thought that exotic fish richness tends to be highest in the lower reaches of the system, with a gradual decrease into upstream reaches. The loss of native fish richness also seems to follow the same pattern, with more losses occurring downstream, fewer upstream. The goal of this presentation is to initially test the above assumptions and to identify what types of streams deserve more focus for actions relative to the impacts of exotic fishes and the reduction of further native fish declines.