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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released 1.6 km upstream of the site (Figure 6). Three or four drift nets (number dependent upon

space available within the breach, which increased with inflow between the first and second

sampling occasions) were set within Breach 2, two in Breach 3, and two downstream from

Breach 3 on the near shore. All drift nets were equipped with a GO Model 2030R mechanical

flow meter suspended in the center of the net to determine the amount of flow passing through

the net. Meters showing incorrect readings were replaced. Depth and flow measurements were

also taken within the breach with the Marsh-McBirney flow meter at the beginning and at the

end of the sampling period if flows changed. The Marsh-McBirney flow meter was also used to

record flow passing through the net at some point during the sampling occasion. This was done

on each sampling occasion at Bonanza Bridge except for the first and last sampling times at

Breach 3, during which little or no entrainment occurred. Samples were collected from nets as

often as needed to prevent backflow, bagged into one-gallon bags, and processed for beads over

the next few weeks.

Total number of beads entrained in the breach was estimated by dividing the breach flow

volume by the total volume of flow sampled by drift nets and multiplying that number by the

total number of beads captured in the nets. Entrainment was usually portrayed as the percent of

flow in the river or percent beads released. Effectiveness of the breach to entrain passive drift

material was portrayed as the percent of total beads captured in the breach compared with the

total number of beads captured at that site.

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