Fish habitat associations in a spatially variable desert stream

White sands pupfish Cyprinodon tularosa were sampled with minnow traps along the length of Lost River, a highly variable desert stream in New Mexico, to evaluate if their abundance, median standard length ( L S ) and sex ratio values differed by microhabitat variables. Habitat measurements were made in a 4 m 2 area around the minnow trap. White Sands pupfish populations were primarily structured by L S . As specific conductance and surface area increased, median size of fish decreased. Shallow areas with higher specific conductance were correlated with an increased number of fish.