9641

• UCREFRP Catalog Number: 9641
• Author: Hedrick, T. N., K. R. Bestgen and K. D. Christopherson.
• Title: Entrainment of Semi-Buoyant Beads and Razorback Sucker, Xyrauchen texanus, Larvae into Flood Plain Wetlands of the Middle Green River, Utah.
• USFW Year: 2009.
• USFW - Doc Type: C-6/RZ-ENTR,
• Copyright Material: NO

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Applying our findings to all flood plain wetlands discussed in the Green River Flood

Plain Management Plan (Valdez and Nelson 2004), flood plain wetlands that will maximize

entrainment oflarval razorback sucker (because they are flow-through sites) are Thunder Ranch,

Stewart Lake, Bonanza Bridge, Above Brennan (RKM 431.3), Johnson Bottom (RKM 422.9),

Leota Bottoms (at flows greater than 431.2 m3/sec), and Old Charley Wash (RKM 402.0) for a

total amount of 1034.3 hectares of inundated wetlands (this is the area of wetlands available

when flows in the Green River reach 526.7m3/sec (18,600 cfs)). However, because of the

sedimentation issue, the Ouray Refuge will no longer operate its flood plain wetlands as flow-

through sites (D. Alonso, Manager, Ouray Refuge, pers. comm.). Thus, the total amount of

hectares of wetlands with flow-through breach configuration (when Green River flows are 526.7

m3/sec) is reduced to only 395.8 hectares.

Remaining flow-through sites (Thunder Ranch, Stewart Lake, Bonanza Bridge [see

discussion above], and Above Brennan) may also have issues that reduce their utility. One

important component of an ideal flood plain not mentioned in The Levee Removal Program

evaluation is the need for razorback suckers to over-winter. This is important because young-of-

year razorback sucker in a flood plain wetland in spring would theoretically not be ready or even

able to move into the river in autumn because there is no connection with the river. Therefore,

while flow-through sites will entrain more razorback sucker larvae, if the flood plain can not

sustain those fish over-winter, the flood plain wetland will not contribute to recovery of the

species. One of us (TNH) sampled Thunder Ranch in the fall of 2006 to determine whether

entrained razorback sucker larvae survived through the summer; none were captured. At least as

importantly, however, was the observation that the Thunder Ranch wetland was only 0.3 to 0.5

meters deep at its deepest point in November. Because average low temperatures in the Uintah

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