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rl (" V Ii. ! 0 H C( t \1\ e 51 .Q ~ eLl. The Progressive Fish-Culturist 60:272-275, 1998 American Fisheries Society. 1998 Evaluation of Razorback Sucker and Colorado Squawfish Batch Marking Techniques .~ G. BRUCE HAINES, STEVEN H. SEVERSON, AND TIMOTHY MODDE* U.S. Fish and Wildlife Service, Colorado River Fish Project 266 West 100 North, Suite 2, Vernal, Utah 84078, USA Abstract.-Young razorback sucker Xyrauchen texanus (mean total length [TL] = 127 mm) and Colorado squawfish Ptychocheilus lucius (mean TL = 150 mm) were marked by freeze branding and injection of a fluorescent elastomer. The elastomer injection was made at the base of the ana] fin and on the 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. E]astomer recognition was better for Colorado squawfish (mean 74%) than for razorback suckers (mean 60%) after 15 months, and retention at both locations was similar. Red and orange had the best recognition and blue had the poorest. Red and orange elastomer injected in young Colorado squawfish could be detected (95%) for 5 months. One person implanting elastomer at two locations on each fish and one person anesthetizing and handling fish can mark 130-140 fish/h. Approximately three times that number can be freeze-branded per hour. Greater retention times and efficiency in marking makes the use of freeze branding a practical replacement for tagging with passive integrated transponders during the first two growing seasons. . Controlled propagation has been identified as an important tool for recovery of the endangered ra- zorback sucker Xyrauchen texanus and Colorado squawfish Ptychocheilus Lucius (Rinne et al. 1986; Johnson and Jensen 1991; Modde et al. 1995). Small numbers of broodfish founders make the ge- netic contribution of each individual important to maintaining genetic diversity. The identification of offspring from paired matings is necessary for equalizing the number of offspring among family lots to achieve maximum effective population size for reintroduction or augmentation of wild popu- lations (Williamson and Wydoski 1994) and for maintaining pedigree records for broodfish devel- opment. Unique broodfish marks are not required until the fish are actually used for spawning; thus, batch marks that separate family lots are sufficient. Marking of family lots can also increase the ef- ficiency of a fish culture facility by allowing the mixing of lots in large grow-out ponds. We use internally implanted passive integrated transpond- er (PIT) tags (Prentice et al. 1990; Burdick and Hamman 1993) for identifying individual fish. However, these tags are expensive, the fish should be at least 75 mm total length (TL), and an elec- tronic scanner is required to read the tag. The use of PIT tags to mark juvenile fish can add significant * Corresponding author: til1Ll11odde@fws.gov 1 Mention of trade names or commercial products does not constitute endorsement by the Recovery Implementa- tion Program for Endangered Fish Species in the upper Colorado River basin. costs to propagation, especially when large num- bers of age-O and age-1 fish are maintained before a reduction to the number of adults used in prop- agation. A simple and inexpensive batch mark that can be used to mark family lots for 1-2 years be- fore implantion of PIT tags will substantially re- duce operation costs. Potential marking methods include freeze branding and the injection of a fluorescent elastic polymer (elastomer). Freeze branding is widely used for marking small salmonids (Mighell1969; Laird et al. 1975; Fay and Pardue 1985; Knight 1990), channel catfish IctaLurus punctatus (Brock and Farrell 1977), and walleyes Stizostedion vi- treum (LaJeone and Bergerhouse 1991), but it has not been tested on razorback suckers or Colorado squawfish. An elastomer was recently developed by Northwest Marine Technology, Inc.] Bonneau et al. (1995) used this technique to mark salmo- nids, Dewey and Zigler (1996) to mark blue gills Lepomis macrochirus, and we used it to mark small (30-70 mm TL) CDIDradD squawfish (Haines and MDdde 1996). A successful mark must have the capability Df providing distinguishably different marks and last fDr 1-2 growing seasons. This study cDmpared the effectiveness Df freeze branding and elastDmer injectiDn fDr identifying family IDts of juvenile fish. Specifically, we ad- dressed three Dbjectives: (1) tD cDmpare freeze branding and visible implant fluDrescent elastomer tags fDr rate Df retention during a 15-mDnth periDd, (2) tD determine if the four available colors Df elastDmer are equally detectable, and (3) to CDm- 272 ~J..LfJ...