A brief (3‐year) study on three headwater streams in the Tonto National Forest, Arizona, documented the immediate effects of wildfire on fishes and their food supply. Hydrologic events following a 1990 wildfire in Arizona effectively extirpated two populations of brook trout Salvelinus fontinalis and one population of rainbow trout Oncorhynchus mykiss. Aquatic macroinvertebrate densities in affected streams (1) declined to near zero within a month after the fire, (2) recovered to only 25–30% of prefire diversity in two of the streams 1 year later, and (3) continued to fluctuate postfire. Salmonid stocks reintroduced into two of the affected streams a year after the fire declined 75% within a year. The quality and quantity of hydrologic events interact after fires in southwestern landscapes and climatic regimes to markedly affect populations of fish and macroinvertebrates. Managers and researchers in the Southwest must be on the alert for field situations that provide an opportunity to cooperatively examine the long‐term effects of both wild and prescribed fires on fishes and on their food supply and habitat.

Critical thermal maxima (CTM) and responses to fluctuating thermal regimes indicate that adult rainbow (Salmo gairdneri), brown (Salmo trutta), and brook (Salvelinus fontinalis) trout species, introduced into the southwestern United States, are as well adapted to elevated water temperature as adult Gila (Salmo gilae) and Arizona (Salmo apache) trout, which are native to that region.

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