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Laboratory Studies Two experiments will be conducted under laboratory conditions to evaluate largemouth bass feeding behavior. The first experiment will involve testing the preference of largemouth bass for selected forage species , and the second will involve testing the preference of bass for a certain size of squawfish. Squawfish will be obtained from Willow Beach NFH, and bass from either the study ponds, other wild sources, or from the San Marcos National Fish Hatchery and Development Center, Texas. For both exper- iments, three 1.33 m diameter circular stock-watering tanks will be used. These will be held at the Utah Water Research Laboratory in Logan. Each will be equipped with a flow-through system using-dechlor- inated city water heated to 22 degrees C and kept at a depth of 37 cm. Each tank will be enclosed and a 15 watt bulb used to light the inter- ior. Light will be set on a timer to maintain a daylength of 14 hours. When food items are placed in a tank, the bass will be partitioned from them until the preyfish have acclimated to the tank environment (0.25-0.5 h). The partition will then be lifted and the enclosed tank left undisturbed until checked the following day.. To determine whether a bass shows a preference for a particular size of young squawfish, or for a particular species when offered in combination, data will be analysed using analysis of variance with the experiment set up as randomized block design (split-plot) where squaw- fish size or prey'species.is the subplot treatment (Neter and Wasser- man 1974). The design-of the species preference experiment is similar to that used by Espinosa and Deacon (1973) and Lewis et al. (1961). Individual • bass are confined in tanks and offered an equal number of _Aifferent kinds of food items. Those items most readily taken are assumed to be preferred by the bass. One bass of each of three different sizes (160-210 mm TL, 250-275 mm TL, and 330-370 mm TL) will be placed in a separate tank and combinations of two species of forage fish offered in numbers of 5-10 per species. Forage species used will be those most commonly found in Colorado River backwaters or those most predominately found in bass stomachs during the first field season. Colorado squaw- fish of similar size will be one of the two species offered in combin- 34