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<br />Muth <br />controls. Survival of larvae during the first 3 days after hatching was 100% in all <br />experimental groups. <br />Otoliths from all larvae treated with ALC or TC as embryos that were examined by <br />UV-light microscopy had fluorescent marks. Intensities of red ALC marks ranged from faint <br />to lucid (mean quality values = 1.0-1.4) in treatments of 5-50 mgll for 12-36 h and lucid to <br />bright (mean quality values = 2.4-3.0) in the remaining ALC treatments. Yellow TC marks <br />were faint to lucid (mean quality values = 1.0-1.6) in treatments of 50 mg/l for 12-36 hand <br />150-450 mg/l for 12 h. For the remaining TC treatments, marks were lucid to bright with <br />mean quality values of 2.6-3.0. <br />Survival of larvae was 85-100% for all treatment combinations in the double-mark <br />experiment; survival of larvae was 90-100% for the controls. Otoliths from all larvae in all <br />ALC: TC treatments had lucid to bright double marks (mean quality values for each mark <br />type = 2.4-3.0). In most otoliths, the outer yellow TC mark of the second treatment slightly <br />overlapped the inner red ALC mark. <br />Our results demonstrated that otoliths of razorback sucker can be successfully <br />marked by immersing embryos or newly hatched larvae in ALC or TC solutions. For best <br />fish survival and mark quality, recommended ALC treatments are 12-30 h in 150-350 mg/l <br />for embryos and 6-18 h in 12.5-50 mg/l for larvae. Recommended TC treatments are <br />18-30 h in 150-350 mg/l for embryos and 6-18 h in 150-350 mg/l for larvae. We used <br />distilled water as the diluent because Hettler (1984) reported that tetracyclines chelate with <br />calcium and magnesium in water, thereby reducing effective concentrations for marking of <br />otoliths; we expected the same to be true for ALC. However, other investigators (e.g., <br />Tsukamoto, 1985, 1988; Dabrowski and Tsukamoto, 1986; Lorson and Mudrak, 1987) have <br /> <br />5 <br />