Laserfiche WebLink
<br />. <br /> <br />. <br /> <br />sampling occasion (R. Brunson, UDWR, pers. comm.). Beads captured on the first and third <br /> <br />sampling occasions were captured near shore in an eddy near the breach mouth and can not <br /> <br />correctly be considered entrainment. During the second release, water was flowing rapidly into <br /> <br />L-7 over the downstream breach (if the upstream inlet breach had not been occluded with <br /> <br />vegetation and sediment, the downstream breach would have been the outlet) and flows were up <br /> <br />to 0.5 m deep, and up to 0.5 m/sec velocity. Thus, only during the second sampling occasion <br /> <br />were beads and water actively entrained. During the first sampling occasion, flows were <br /> <br />apparently stable and not of sufficient stage for water to be entrained into L-7. During the third <br /> <br />sampling occasion, river stage was declining so the wetland was draining. One of us (KRB) <br /> <br />witnessed a yellow bead (apparently from release two) exiting L- 7 during the third release <br /> <br />sampling, supporting the notion that water and beads were not being entrained at that time. This <br /> <br />may be a typical pattern for single breach wetlands, which entrain water, beads, and fish larvae <br /> <br />only when filling, but during equilibrium or declining river stage, do not entrain anything or <br /> <br />drain. Although some entrainment likely occurs in single breach wetlands when daily flows <br /> <br />pulse up and down in the spring runoff period, the amount of flow and particles entrained is <br />likely low when wetlands are mostly filled. <br /> <br />Beads and larvae were captured in the Green River at L- 7 during each release. Larvae <br /> <br />detected in the near and far shore nets were not necessarily marked larvae from the study. <br /> <br />However, because the only known spawning bars in this reach of river are in the Jensen area, <br /> <br />those larvae likely traveled a long distance to be captured in our nets. Although not many larvae <br /> <br />were observed in these samples, we did capture many beads, and these observations may point to <br /> <br /> <br />a need to refine the Flood Plain Drift Model (Valdez and Nelson 2004) that predicts that only 1 % <br /> <br /> <br />oflarval fish will remain in the drift 58 kilometers downstream from the spawning bars. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />42 <br /> <br />. <br />