EVALUATION OF RAZORBACK SUCKER AND COLORADO SQUAWFISH BATCH MARKING TECHNIQUES

Young razorback sucker Xyrauchen texanus (mean total length [TL] = 127 mm) and Colorado squawfish Prychocheilus lucius (mean TL = 150 mm) we re marked by freeze branding and injection of a fluorescent elastomer. The elastomer injection was made at the base of the anal fin and on t he operculum (razorback suckers) or lower jaw (Colorado squawfish) and consisted of one of four colors: green, blue, red, or orange. Freeze branding had 99% retention after 15 months for both species. Elastomer recognition was better for Colorado squawfish (mean 74%) than for raz orback suckers (mean 60%) after 15 months, and retention at both locat ions was similar. Red and orange had the best recognition and blue had the poorest. Red and orange elastomer injected in young Colorado squa wfish could be detected (95%) for 5 months. One person implanting elas tomer at two locations on each fish and one person anesthetizing and h andling fish can mark 130-140 fish/h. Approximately three times that n umber can be freeze-branded per hour. Greater retention times and effi ciency in marking makes the use of freeze branding a practical replace ment for tagging with passive integrated transponders during the first two growing seasons.