WSP07323

• File Number: 8240.300.31.J
• Description: San Juan River - Environmental Studies
• Basin: San Juan/Dolores
• Water Division: 7
• Date: 10/3/1996
• Title: Biological Opinion on the Proposed Experimental Stocking of Early Life Stage Colorado Squawfish in the San Juan River
• Water Supply Pro - Doc Type: Biological Opinion

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Mixer to Hogback (AM 131 to AM 154)
Hogback to Animas (AM 155 to AM 180)
Animas to Blanco (RM 181 to RM 213)
Blanco to Navajo Dam (RM 214 to RM 2241

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The experimental stocking design proposed by the State of Utah and approved by the
Coordination Committee for inclusion in the Program's 1996 research effort involves a 2-
year effort of stocking and monitoring in 1996 and 1997. Approximately 100,000 Age-1
sized Colorado squawfish (70-90 mm) will be obtained the first year from Dexter National
Fish Hatchery in Dexter, New Mexico and experimentally stocked to determine the
overwinter survival of stocked Colorado squawfish at this size during an expected low
flow winter. Monitoring these fish will also aid in the determination of what habitats are
utilized by Colorado squawfish of this size. An equal number of Age-O sized Colorado
squawfish (50 mm) will be stocked in 1997. The objectives of the 1997 stocking efforts
are to determine if the quality and quantity of low-velocity habitats in the San Juan River
are sufficient to support retention and recruitment of young-of-year Colorado sQuawfish,
and to determine the effects of diversion canals on young-of-year Colorado squawfish
movement and survival.

In late October/early November, it its proposed that 100,000 juvenile Colorado squawfish
obtained from Dexter National Fish Hatchery will be stocked into the San Juan River. The
otoliths of these fish have been marked with a tetracycline hydrochloride (TC) stain. Half
(50,000) of these fish will be stocked into the upper San JJJan River (Mixer Reach RM
131-126) and the remaining half into the lower San Juan (John's Canyon RM 25-201.
These reaches were chosen for two reasons: 1) the upper reach is just below the only
known spawning bar in the San Juan River and has a high concentration of nursery
habitats and 2) the lower reach is low-gradient, has a high concentration of nursery
habitat, and is proximal to locations where the highest concentration of wild larval
Colorado squawfish have been caught (19 of 21 have been captured below RM 13). The
2 lots of 50,000 fish will be spray marked to allow field researchers to differentiate
between the two stocking groups, The spray mark should last into the spring/summer of
1997, After that period. captured fish will be sacrificed to differentiate between stocked
and wild specimens via the TC otolith markings. Tetracycline hydrochloride is a water
soluble fluorescent chemical that becomes incorporated into otoliths of marked fish. The
captured fish must be killed in order to obtain the otoliths and determine the markings.
Objective No, 8 of the proposed action will use information from field collections as well
as a lab component to determine the retention time of the spray mark. The lab component
will hold a sample of spray marked fish in captivity to determine retention times for the
spray marks and. thus, their feasibility for use in non-lethal monitoring efforts.

One week following the October/November stocking, a representation of all habitats,
including low-velocity habitats will be sampled throughout the two stocked reaches, This
initial sampling will determine what habitats are being used and the movements of the
stocked fish. The 2 reaches will then be sampled 1 month following the stocking.
Sampling will then be coordinated with the regularly scheduled Utah Division of Wildlife
Resources nursery habitat trips.. late March/early April to determine overwinter survival;
late August to intensively sample low-velocity habitats; and September to characterize fish
communities in low-velocity habitats and prior to winter stresses).

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