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The northern pike is a large (> 1300 mm) member of the family Esocidae. Juvenile and adult northern pike are strongly piscivorous; however, young pike (<50 mm) feed primarily on insects and crustaceans (Hunt and Carbine 1951; Frost 1954). Although northern pike become strongly piscivorous as they mature, Chapman et al. (1989) and Chapman and Mackay (1990) reported that invertebrates may be important food items seasonally. Because northern pike feed by sight, their growth rates may be hindered by high turbidity-a physical characteristic common to many western rivers. Male northern pike become sexually mature around ages 2 or 3 and most females reach maturity by age 3 (Carlander 1969). Crossman (1979) reported life expectancy of northern pike to be at least 24 years. Northern pike are typically found in small lakes, vegetated portions of larger lakes, and rivers (Crossman 1979). Miller and Rees (1997) found that northern pike in the Yampa River, selected pools as habitat, although they also documented use of backwaters. Carlson et al. (1979) did not obtain northern pike in fish collections from July 1975 to October 1977 in the Yampa River between Dinosaur National Monument and the town of Hayden, Colorado. Nesler (1995) found that northern pike occupied the same pool habitats as Colorado pikeminnow. The percent composition of northern pike, for all fish over 15 cm, was estimated to be 1.5% downstream of Sunbeam (RM 60-64) and 4.1 percent 50 miles upstream near Duffy Tunnel (Anderson, in press). Smallmouth bass are sight dependent carnivores during all life stages. At an early age they feed on plankton and aquatic invertebrates, but eventually switch to small fishes (sometimes other small bass) and crayfish (Car lander 1977; Stephenson and Momot 1991). Lachner (1950) found that smallmouth bass over 60 mm consumed primarily crayfish and fish, while bass smaller than 40 mm consumed only crayfish. Females become sexually mature between ages 4 to 6, at which time they are usually able to produce one brood per year. Males become sexually mature at ages 3 to 5 (Cross and Collins 1975; Pflieger 1975). Carlander (1977) listed the maximum life span for smallmouth bass as about 18 years. Smallmouth bass of all ages occur in rocky habitat, but they also use log jams and root wads. Rankin (1986) reported that smallmouth bass habitat selection in the Flat River, Michigan, was influenced by abiotic factors such as depth, velocity and substrate, but he also hypothesized that prey distribution was important to habitat selection. Probst et al. (1984) demonstrated that habitat use by smallmouth bass is life stage specific. Smallmouth bass smaller than 350 mm were found associated with faster water velocities, vegetation, and boulders more often than larger smallmouth bass, which chose log jams and slower current velocities. Smallmouth bass avoid water with a pH less than 6.0, and require dissolved oxygen concentrations of greater than 0.96 ppm at a water temperature of 21 oC (Carlander 1977). 37