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t It is important to consider possible beneficial actions of higher arsenic levels to fish (greater than NCBP 85th percentile). Arsenic is a known fungicide (Moore and Ramamoorthy 1984) and has been used in veterinary medicine to treat parasitic diseases (Eisler 1988). It is possible that higher arsenic levels in a hatchery situation may actually prove to be beneficial. This possibility warrants further investigation. Copper residue levels in Hotchkiss hatchery trout were also high, at 3X the 1980-81 NCBP 85th percentile (Lowe et al 1985). Colorado squawfish copper residue levels were all below the 1980-81 NCBP mean value of 2.72 ug/g dry weight, except for Colorado squawfish #4 which contained 4.11 ug/g dry weight copper, (higher than the NCBP 85th-percentile). Again, Colorado squawfish n4 may have accumulated some copper from either food or water at Hotchkiss hatchery, or from the White River. Hotchkiss hatchery trout contained low levels of mercury in tissues. Colorado squawfish, however, accumulated high mercury levels from the White River, from 1.5 to 5.5X the 1980-81 85th percentile of 0.72 ug/g dry weight. These Colorado squawfish were very old fish (approx. 10-25 yrs old). Accumulation of mercury by aquatic biota tends to be rapid, and depuration slow (Eisler 1987). The high mercury levels in these squawfish are somewhat expected, as increases in mercury concentration with size and age of fish seems to be a universal trend (Phillips et al 1987). Levels of cadmium found in squawfish can probably also be attributed to the White River, because Hotchkiss hatchery trout samples contained low levels. On April 2, 1987, two channel catfish were collected from the Colorado River, and sent to the Environment Trace Substances Research Center, Columbia, Missouri for inorganic trace element analysis. Results are listed in Table 3. Comparisons were made between these values, and levels found in three Colorado