8022

• UCREFRP Catalog Number: 8022
• Author: Muth, R. T., et al.
• Title: Reproduction and Early Life History of Razorback Sucker in the Green River, Utah and Colorado, 1992-1996.
• USFW Year: 1998.
• USFW - Doc Type: 34,
• Copyright Material: NO

juvenile sizes in aquaria and then identified and counted. Some larger fish, particularly from
seine collections, were identified, measured, counted, and released in the field,
Lower Green River.-Exploratory sampling in 1993 and 1994 was mostly opportunistic
and occurred at irregular intervals during mid-June (1993) or mid-May through mid-June (1994).
Collections in 1995 and 1996 were made about twice per week during late April through late
July, Seines and light traps were used to sample quiet-water habitats throughout the 4 years of
collecting. Seines were 1.2 m deep X 1.2 m long with 0,8 mm mesh, 1.2 m deep X 3.0 m long
with 1.6 mm mesh, or 1.5 m deep X 4,0 m long with 1.25 mm mesh. Three to 10 light traps with
2- or 4-mm wide entry slits were deployed per habitat and collection date. Most fish collected
were preserved in 100% ethanol, but some were fixed in 10% formalin. In 1994, sucker larvae
(N = 41) from nine light-trap samples were immobilized with aqueous solutions of the anesthetic
tricaine (FinqueI™) at 1 00 mglL (Snyder 1997); identified, measured, counted, and allowed to
recover in the field; and then taken to the laboratory for rearing (Muth and Wick 1997).
Juveniles of endangered Colorado squawfish Ptychocheilus lucius and some other larger fish
collected with seines were identified, measured, counted, and released in the field.

Laboratory Procedures

Fish in each collection were sorted from debris, transferred to fresh 100% ethanol (those
originally preserved in 100% ethanol) or 3% phosphate-buffered formalin (those originally fixed
in 10% formalin), and identified to species using morphological criteria (e.g., Snyder 1981;
Snyder and Muth 1990). The identity of selected native sucker larvae collected in 1993 was
verified by mitochondrial DNA analysis (Proebstel 1998). Larvae of native suckers were
measured to the nearest mm TL and counted; razorback sucker larvae selected for otolith aging
were measured to the nearest 0.1 nun TL. Specimens of other fishes smaller than 41 mm TL
were grouped and counted by 5-mm TL intervals, whereas larger fish were grouped as greater
than 40 nun TL and counted,
Randomly selected razorback sucker larvae collected each year during 1993-1996 from
nursery habitats in the middle or lower Green River and preserved in 100% ethanol were aged by
counting daily increments in otoliths from hatching to capture. Preliminary results of a

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