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l
<br />ti
<br />June 1995
<br />Notes
<br />50 mg/1 for 12 to 36 h and lucid to bright (mean
<br />quality values = 2.4 to 3.0) in the remaining ALC
<br />treatments. Yellow TC marks were faint to lucid
<br />(mean quality values = 1.0 to 1.6) in treatments
<br />of 50 mg/1 for 12 to 36 h and 150 to 450 mg/1
<br />for 12 h. For the remaining TC treatments, marks
<br />were lucid to bright with mean quality values of
<br />2.6 to 3.0.
<br />Survival of larvae was 85 to 100% for all treat-
<br />ment combinations in the double-mark experi-
<br />ment; survival of larvae was 90 to 100% for the
<br />controls. Otoliths from all larvae in all ALC : TC
<br />treatments had lucid to bright double marks (mean
<br />quality values for each mark type = 2.4 to 3.0).
<br />In most otoliths, the outer yellow TC mark of
<br />the second treatment slightly overlapped the inner
<br />red ALC mark.
<br />Our results demonstrated that otoliths of ra-
<br />zorback sucker can be successfully marked by
<br />immersing embryos or newly hatched larvae in
<br />ALC or TC solutions. For best fish survival and
<br />mark quality, recommended ALC treatments are
<br />12 to 30 h in 150 to 350 mg/1 for embryos and
<br />6 to 18 h in 12.5 to 50 mg/1 for larvae. Rec-
<br />ommended TC treatments are 18 to 30 h in 150
<br />to 350 mg/1 for embryos and 6 to 18 h in 150 to
<br />350 mg/1 for larvae.
<br />We used distilled water as the diluent because
<br />Hettler (1984) reported that tetracyclines chelate
<br />with calcium and magnesium in water, thereby
<br />reducing effective concentrations for marking of
<br />otoliths; we expected the same to be true for ALC.
<br />However, other investigators (e.g., Tsukamoto,
<br />1985, 1988; Dabrowski and Tsukamoto, 1986;
<br />Lorson and Mudrak, 1987) have used tap water
<br />or natural freshwater to prepare tetracycline or
<br />ALC solutions at concentrations similar to ours
<br />with no reported problems. Also, otoliths in early
<br />larvae of razorback sucker (<_12 days old, post-
<br />hatching) reared at Ouray Fish Hatchery, Utah,
<br />were successfully marked with a TC treatment
<br />of 350 mg/1 for 6.5 h using dilution water with
<br />total hardness of about 150 mg/1 (R. T. Muth,
<br />pers. obser.). If water having high total hardness
<br />is used to prepare ALC or TC solutions, concen-
<br />trations of these chemicals may have to be in-
<br />creased beyond recommended levels in distilled
<br />water for successful marking of otoliths.
<br />Tsukamoto (1988) stated that multiple treat-
<br />ments with one or more chemicals of different
<br />fluorescent colors can provide many variations of
<br />otolith marks for uniquely marking different
<br />batches of fish. In our two-chemical double mark-
<br />243
<br />ing of otoliths in newly hatched razorback sucker
<br />larvae, complete separation of marks was not
<br />achieved with a 24-h interval between treatments.
<br />However, presence of a double mark was obvious
<br />because of sharp contrast between the red ALC
<br />and yellow TC fluorescence. A similar observa-
<br />tion was made by Tsukamoto (1988) for ayu
<br />(Plecoglossus altivelis) that had been treated with
<br />ALC as embryos and again, two to three days
<br />later, with TC as newly hatched larvae. In mul-
<br />tiplemarking with one fluorescent chemical, com-
<br />plete separation between marks is necessary for
<br />accurate recognition of different marking pat-
<br />terns. Dabrowski and Tsukamoto (1986) marked
<br />otoliths in juveniles of peled (Coregonus ~eled)
<br />with TC at three, 6- to 7-day intervals and re-
<br />ported good separation between marks. Good sep-
<br />aration of double TC marks in otoliths of razor-
<br />back sucker larvae reared at Ouray Fish Hatch-
<br />ery was achieved with a 7-day interval between
<br />treatments (R. T. Muth, pers. obser.). Longevity
<br />of ALC or TC marks in otoliths of razorback
<br />sucker is unknown, but they have been reported
<br />to persist in otoliths or vertebrae of other fish
<br />species for at least one to several years (Weber
<br />and Ridgway, 1967; Tsukamoto, 1988).
<br />This study was funded by the Recovery Im-
<br />plementation Program for Endangered Fish Spe-
<br />cies in the Upper Colorado River Basin. The
<br />recovery program is a joint effort of the U.S. Fish
<br />and Wildlife Service, U.S. Bureau of Reclama-
<br />tion, Western Area Power Administration, states
<br />of Colorado, Utah, and Wyoming, upper basin
<br />water users, and environmental organizations. We
<br />thank R. Hamman (Dexter National Fish
<br />Hatchery and Technology Center, Dexter, New
<br />Mexico) for providing razorback sucker eggs.
<br />Comments by K. Bestgen, L. Grist, G. Haines,
<br />T. Modde, T. Nesler, D. Snyder, and two anon-
<br />ymous reviewers improved the manuscript. This
<br />paper is contribution no. 77 of the Colorado State
<br />University Larval Fish Laboratory.
<br />LITERATURE CITED
<br />BROTHERS, E. B. 1990. Otolith marking. Amer. Fish.
<br />Soc. Symp., 7:183-202.
<br />BUCKLEY, R. M., AND H. L. BLANKENSHIP. 1990.
<br />Internal extrinsic identification systems: overview
<br />of implanted wire tags, otolith marks, and parasites.
<br />Amer. Fish. Soc. Symp., 7:173-182.
<br />DAaxowsxl, K., AND K. TSUKAMOTO. 1986. Tetra-
<br />cycline tagging in coregonid embryos and larvae. J.
<br />Fish Biol., 29:691-698.
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