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t 1 t 1 1 1 D LC50 values (0.04778 mg/L) reported for juvenile bluegill by Smith et al. (1976), pockets of higher levels may have been present in the pond or overall levels may have been higher prior to ice-out. Burdick (1978) extensively sampled Pelican Lake, Utah, for H2S after previously observing bluegill winterkill there; he found elevated levels of H2S to be patchy in distribution and significantly higher two weeks prior to ice-out than at ice-out (0.00-2.50 vs 0.00-0.044 mg/L). We sent samples of dead and dying squawfish collected from West Pond to Fort Morgan Disease Control Center for necropsy. Pathologists there found ' large numbers of Aeromonas and Pseudomonas bacteria in the kidneys but suggested that such secondary invaders often cause disease when fish I 1 I 1 t t 1 t t become stressed from other causes. Though they did not look specifically for evidence of H2S toxicity, and therefore did not rule it out as a possibility, they concluded that the "overload" of Asian tapeworms they found in digestive tracts (36-45 adult, 40-mm-long worms/fish) was no doubt the primary etiologic agent (Phyllis Barney, personal communica- tion). 13th-Hole Pond Growth Because Colorado squawfish were stocked into 13th-Hole Pond early in 1986, their growing season that year was at least three months longer than was that of fish stocked in Fish Chalet and West ponds. In addition, mean length of these fish was twice that of those of the other ponds when stocked (Fig. 1). The lower stocking density and larger individual size enabled these fish to better utilize the forage base of fathead minnows present in 13th Hole Pond. Mean length during 1986 increased from 94.2 mm 30