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To determine the contribution of stocked bass to the bass population in Chatfield, electrofishingwas conducted during the spring of each year. A boat mounted electrofishing unit was used which utilized a 5000-w gener- ator and pulse DC current. Length and weight measurements and scale samples were obtained from all bass captured. Bass were then inspected under UV light to detect marks and released. Ages of all bass were determined and the proportion of stocked bass to all bass in a given year-class was calculated. A creel census was conducted from May through September in 1981 and 1982 to assess angler utilization of bass. A random-stratified schedule of 4 weekend days and 5 weekdays was used. Contacts and counts were made along the entire shoreline of the reservoir with boat anglers being interviewed upon leaving the lake. During 1982, all cree led bass were checked for pigment marks using equipment described by McAfee (1980). RESULTS AND DISCUSSION The number of largemouth bass stocked into Chatfield Reservoir varied from 3,100 in 1979 to 16,800 in 1981 (Table 1). Corresponding stocking rates for those years were 10 and 54 bass per habitat-acre, respectively. Although the target stocking rate of 50jH.A. was only met in 1981, numbers of bass stocked in other years was considered adequate to assess their contribution. Table 1. Largemouth bass stocked in Chatfield Reservoir, Colorado. Date of No. Average No. per stocking stocked size (nun) habitat-acre 27 June 1979 3,100 128 10.0 13 June 1980 5,460 131 18.0 8 June 1981 16,800 120 54.0 4 June 1982 13,090 123 42.0 The limited production of bass at the Wray Hatchery during 1978 and 1979 was principally due to sporadic spawning of brood bass which resulted in unequal sizes of fry and large losses from cannibalism. In addition, the hatchery experienced problems with abundance and timing of plankton blooms, low artificial diet training success, handling stress, and power failures. Since that time, personnel at Wray have increased bass production by (1) maintaining brood bass in cool-water raceways until spawning conditions are ideal, (2) increasing fertilization of rearing ponds, (3) improving feeding techniques, (4) careful attention to sorting, and (5) treatment of disease. The proportion of stocked bass to all bass of the same age-class sampled during spring electrofishing varied from 9-59% during 1979 to 1982 (Table 2). The contribution of stocked bass to the 1978 year-class was relatively con- stant during all 4 years of sampling. Returns of the hatchery-reared 1979 year-class were much more variable, however, composing 94%, 59%, and 26% of the total year-class in 1980, 1981, and 1982 respectively. S~pling bias 56