SPATIAL HABITAT SELECTION OF ROUNDTAIL CHUB (GILA-ROBUSTA) IN 2 CENTRAL ARIZONA STREAMS

We developed habitat suitability indices for depth, velocity, substrat e, and cover for adult and juvenile roundtail chub (Gila robusta) and razorback sucker (Xyrauchen texanus) (220-290 mm TL) in Fossil Creek, and adult roundtail chub in Wet Beaver Creek, central Arizona. Adult r oundtail chub in Fossil Creek selected wider ranges of velocity (0 to 0.96 mps) and depth (0.9 to 3.1 m) than juveniles (0 to 0.61 mps veloc ity and 0.9 to 1.5 m depth). Adult roundtail chub in Fossil Creek sele cted small-boulder and gravel substrates, and large instream objects. Juveniles selected a variety of substrates, particularly sand, but sho wed little selection for bedrock and large boulders. They did select f or other types of cover. Adult roundtail chub in Wet Beaver Creek sele cted low velocity areas and did not use velocities >0.14 mps. Most adu lts in Wet Beaver Creek selected depths of about 2.1 m. Few fish selec ted greater and lesser depths. Adults selected bedrock and large bould er substrates and instream cover. Razorback sucker in Fossil Creek cho se velocities <0.3 mps and showed the highest selection for velocities of 0.15 mps. They selected depths between 1.5 and 2.7 m, most commonl y choosing depths of 2.0 m. Most razorback suckers occurred over silt substrates, but small and large boulders and bedrock were also used. S and and gravel were not utilized. Razorback suckers used large, instre am objects and instream overhead cover but also used other types of co ver.