9533

• UCREFRP Catalog Number: 9533
• Author: Muth, R. T. and E. Wick.
• Title: Field Studies on Larval Razorback Sucker in Canyonlands National Park and Glen Canyon National Recreation Area, 1993-1995.
• USFW Year: 1997.
• USFW - Doc Type: Fort Collins.
• Copyright Material: NO

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Marking Otoliths in Larval Suckers: 1995 (Objective 3)

Background.-Field mark-capture studies on razorback sucker larvae would facilitate
investigation of early biology and recruitment. Marking otoliths of fish has great potential for
use in stock identification, assessment of stocking success, and life-history studies (Brothers
1990; Buckley and Blankenship 1990). One technique for rapid mass marking is incorporation
of fluorescent chemicals in otoliths by immersion of fish embryos or larvae in solutions of these
chemicals. Two compounds proven effective for this technique are alizarin complexone (ALC)
and tetracycline hydrochloride (TC). Once deposited in bone, ALC fluoresces red and TC
fluoresces yellow when illuminated by ultraviolet (UV) light. Single or multiple treatments with
either or each of these chemicals can be used to produce potentially long-term marks unique to
different batches of fish with virtually 100% initial marking success (Tsukamoto 1985, 1988;
Dabrowski and Tsukamoto 1986; Muth et al. 1988; Brothers 1990). Muth and Meismer (1995)
adapted this technique for use on captive embryos and larvae of razorback sucker. They
recommended ALC treatments of 12-30 h in 150-350 mgll for embryos and 6-18 h in 12.5-50
mg/l for larvae, and TC treatments of 18-30 h in 150-350 mgll for embryos and 6-18 h in
150-350 mg/l for larvae.

Methods.-Approximately 50 larvae of f1annelmouth sucker Catostomus latipinnis
(intended as a surrogate for razorback sucker) collected with light traps from Millard Canyon or
the Bonita Bend area were immersed alive for 6 h in buffered solutions (pH, 6.8) of 50 mg ALC
or 350 mg Tell distilled water. After treatment, living larvae were placed in 1-m wide X 1-m
long X 1.3-m deep enclosures constructed of 500-11 mesh nitex nylon, which were located in
water about 0.75 m deep in Millard Canyon or the Bonita Bend area. Subsamples of these
larvae were removed from the enclosures at 1-d intervals post-treatment over 4-d periods,
preserved in 100% ethanol, and taken to LFL for examination. In the laboratory, sagittae and
lapilli (otoliths) were extracted from each larva, mounted whole in glycerin on glass slides, and
examined with incident UV light under a compound fluorescent microscope for presence and
intensity of the f10urescent mark. Intensity of the mark in otoliths from each larva was ranked
as absent, faint, lucid, or bright. The number of daily growth increments between time of
marking and time of subsampling were counted.

Enclosures to Study Growth and Survival of Razorback Sucker Larvae: 1995 (Objective
4)

This experiment was not conducted due to low numbers of sucker larvae collected (see
results of fish collections). The planned experimental design was as follows.
An experiment using fish enclosures in nursery habitats of the lower Green River within
CANY will be conducted to assess differences in survival and growth of larval native suckers as
a function of changes in degree of predation by adult red shiner and abundance and
composition of food resources related to development of sucker larvae and temporal variations
in environmental conditions. Use of enclosures in nursery habitats will allow for control to
produce quantifiable results in a natural setting. It is unlikely that sufficient numbers of
razorback sucker larvae will be collected for the experiment, so larval flannel mouth or bluehead
suckers will be used as surrogates.
Each fish enclosure will be 1 m wide X 1 m long X 1.3 m deep (open at top and closed
at bottom) and constructed of 500-11 mesh nitex nylon; this mesh size will retain sucker larvae
and allow for passage of food items, primarily zooplankton and other small invertebrates. Six

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