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METHODS <br />Substrate and velocity preferences of one-year old bonytail were tested using artificial <br />stream tanks with simulated backwaters and variable flow regimes. Substrate types <br />tested included sand, gravel, and cobble. Velocities ranged from low to high. <br />Observations were made with and without red shiners during both daytime and <br />nighttime hours and were repeated in the stream tanks. <br />Three hundred juvenile (one-year old) bonytail were acquired from Dexter National Fish <br />Hatchery in Dexter, New Mexico. The fish were held in a circular tank (92 cm radius x <br />40 cm water depth) at 18°C until they the experiment began. Twenty-five of the bonytail <br />were held and fed in a holding tank set up with intermittent flow (1 hour of flow/ 3 hours <br />of no flow) to begin physically acclimating them to flow. Velocities ranged from 0.05 to <br />0.08 m/s in the holding tanks. <br />There were four rectangular artificial stream tanks for the actual experiments. Two <br />tanks were used for substrate experiments and two were used for flow experiments. <br />Each tank was 305 cm long x 94 cm wide x 27 cm water depth. The center of each <br />tank was divided lengthwise by a piece of plexiglass. Marks were made on the <br />plexiglass at 20 cm intervals in order to visually divide the channel into sections to aid in <br />locating horizontal fish positions and mapping flows. Screens were installed to allow <br />water to travel in a circular motion when pumps were added and to isolate the pumps <br />from the rest of the tank. <br />A 12 hour light/dark light regime was used. One fluorescent and one gro-light bulb were <br />placed over each of the four tanks. Night observations were made possible by the use <br />of a red light which was on from 0700-0900. <br />11