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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entrainment rates were highest at the second highest river flow stage and declined after that

(Tables 13 and 14, Figure 18). In addition, entrainment effectiveness (percentage of beads

captured in the breach vs. in the near shore nets) was also highest on the first sampling occasion,

before the peak (Table 14). We are not sure why this scenario would occur but assume it is due

to an anomalous bead distribution, erratic movement during entrainment, or breach elevation and

sediment dynamics. There is a large sandbar on river left that begins just upstream of Breach 2

and it is possible that at lower flows, more entrainment can occur and that at higher flows, more

beads are swept away from the breaches with the thalweg. Flow entrainment at comparable river

flow levels on the ascending and descending limbs ofthe hydrograph were similar, again

suggesting that entrainment rates may not vary for flow-through wetlands whether they are

receiving water during the time when river stage is increasing or decreasing.

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Implications for flood plain wetland management in the middle Green River

A logical discussion point for future management of flood plain wetlands is what

combination of flow-through and single breach types are needed to assist with recovery of

razorback sucker in the middle Green River. The evaluation ofthe Levee Removal Project

discussed numerous points regarding the elements of an ideal flood plain wetland (Birchell et al.

2002) and should be included in this discussion. These elements included:

. site configuration to maximize entrainment of drifting razorback sucker larvae;

. refuge from predation by native and nonnative predators;

. high productivity to allow rapid growth of razorback suckers;

. a lack of ability to produce nonnative fish;

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