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Gunnison River inflow. Our study reaches corresponded to the food-availability study reaches 9-B and 9-C in the 15-mile reach and 8-A and 8-B in the 18-mile reach (see Osmundson in review). These reaches were selected primarily for logistical reasons: monitoring these study reaches allowed us to launch a boat at the Corn Lake launch and later pull out at the Fruita Bridge launch. By not sampling reaches 9-A and 8-C, travel time on the river was shortened allowing for more time to sample additional sites. Locations of sampling sites were recorded in river kilometers (rk) from the Green River confluence (rk 0.0); these were converted from river mile maps developed by the Colorado Division of Wildlife. In addition, site locations were recorded in longitude and latitude coordinates using a Precision Lightweight Global Positioning System (GPS) Receiver (Rockwell International) that calculates position coordinates from signals transmitted from Navstar satellites (Fig. 4). Site locations are listed in Table 4 (Appendix). A given sampling effort was conducted during one 8-hr work day by a team of two people. Sampling was conducted during the descending limb of the spring hydrograph and during the base flow period of summer and fall. Within each study reach a minimum of one run and one riffle was sampled. The study sites selected were the first suitable sites encountered while proceeding downstream from the top of each study reach. Suitable sites were ones that had cobble exposed during runoff and base flow. River depth and current strength precluded sampling of substrate in the center of the river. Additionally, we assumed that conditions in cobbles on exposed bars above the water level or in shallow water along the shore were not reflective of conditions out in the river under flowing water. This was because fine sediment settles in low velocity conditions found along the shoreline. As the river recedes, a drape of fine sediment is left on the newly exposed rocks which were recently under the calm depositional waters of the shoreline zone. We therefore waded into the river far enough for two conditions to be met: 1) the water was between 3045 cm deep and 2) the current velocity was at least 0.3 m/s (Marsh McBirney model 201 portable water current meter). To measure embeddedness, the technique consisted of first laying one hand flat on top of the cobble surface layer. Holding the other hand perpendicular to the first, the fingers were extended down between the thumb and forefinger of the first until the tip of the index finger reached the layer of embeddedness. Rocks adjacent to the one the first hand laid atop often had to be pushed aside before the embeddedness layer was located. The embeddedness layer was judged to be reached when moderate effort was unable to extend the middle finger any deeper. Both hands were then pulled up in a fixed position and the distance was measured (to the nearest 0.5 cm) from the tip of the extended finger to the palm of the horizontal hand (Fig. 5). Twenty measurements of embeddedness were taken per site during a given sampling effort. Any biases from differences in measurer technique were minimized by having each person measure half of the samples at each site (this also helped minimize soreness of fingers). A measurer would wade parallel to the shore and take a measurement every two steps. The measurer looked forward while placing the hand on top of the rocks to minimize placement 6