Catastrophic wildfire and number of populations as factors influencing risk of extinction for Gila trout (Oncorhynchus gilae)

We used the computer program RAMAS to explore the sensitivity of an extinct ion-risk model for the Gila trout (Oncorhynchus gilae) to management of wil dfires and number of populations of the species. The Gila trout is an endan gered salmonid presently restricted to ver), few headwaters of the Gila and San Francisco river tributaries in southwestern New Mexico. Life history. data for 10 extant populations were used to examine sensitivity of the spec ies viability to changes in a variety of factors including population size, fecundity, life stage structure, number of populations, severity and proba bility of forest fires, and a regulated fishery. The probability and. sever ity of forest fires and number of populations had the greatest effect on vi ability. Results indicate that successful conservation of Gila trout requir es establishment of additional populations and reduction of the severity of forest fires through a program incorporating more frequent, but less sever e, fires.