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Executive Summary Young razorback sucker Xyrauchen texans and Colorado squawfish Ptychocheilus lucius were marked by freeze branding and fluorescent elastic polymer (elastomer), The elastomer implant was located at the base of the anal fin and on the operculum (razorback sucker) or lower jaw (Colorado squawfish) and consisted of one of four colors: green, blue, red, or orange. Freeze branding had retention rates of 99% after 15 months for both species, Elastomer recognition was better for Colorado squawfish (grand mean 74%) than razorback sucker (grand mean 60%) after 15 months, No elastomer location proved to be superior to the others. Red and orange had the best recognition, blue the poorest. The red and orange elastomer implant for young Colorado squawfish had five month retention rates of 95%. Given these results the following recommendations are proposed, 1, Freeze branding had excellent retention for 15 months for both razorback sucker and Colorado squawfish and could easily substitute for the use of internally implanted passive integrated transponder (pIT) tags following the first growing season, 2, Elastomer recognition, although acceptable for.short time periods (red ~d orange) on Colorado squawfish, are not recommended for marking fishes if identification is desired beyone 12 months, 3, One person implanting elastomer at two locations on each fish and one person anesthetizing and handling fish can mark 130-140 fish per h, Approximately three times that number can be freeze-branded per h, The greater retention time and efficiency in marking makes the use of freeze branding the practical replacement for PIT tagging during the first two growing seasons of hatchery reared fishes, 5