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Last modified
7/14/2009 5:02:34 PM
Creation date
5/22/2009 5:01:43 PM
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UCREFRP
UCREFRP Catalog Number
9319
Author
Mueller, G., M. Horn, Q. Bradwisch and L. Boobar.
Title
Examination of Native Recruitment and Description of the Fish Communities Found in the San Jan and Colorado River Interface Zones of Lake Powell, Utah.
USFW Year
2001.
USFW - Doc Type
01-159,
Copyright Material
NO
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<br />I. <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I, <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />Mapping Description <br /> <br />Bathymetric data were collected using a BioSonics, scientific echo sounder and a Rockwell GPS <br />receiver. A boat with the equipment followed the shoreline and then ran cross-sectional profiles <br />ofthe study area at 0.25-km intervals between RM 48 to 55 in the San Juan arm. The <br />echo sounder processed the data and produced files containing depth and UTM coordinates. This <br />information was run through ARCinfo to develop bathymetric maps. The program also <br />calculated area capacity and water volume tables. <br /> <br />Fishery Studies . <br /> <br />Sample Locations Sampling site locations were recorded in river miles (RM) which <br />started at Lee's Ferry (RM-O) and proceeded upstream to Imperial Rapids (RM-200). River mile <br />designations for the San Juan River began at its (inundated) confluence with the Colorado River <br />(RM-O) and proceeded upstream to Clay Hills Crossing (RM-56). <br /> <br />Fish were sampled at 3 locations: (1) the inflow area of the Colorado River; (2) inflow area of the <br />San Juan rivers; and (3) Spencer's Camp area which served as a reservoir control site. Sampling <br />in the inflow areas was adjusted with changes in reservoir elevation and river stage but remained <br />constant at Spencer's Camp from RM-38 and 39.5 (Figure 1). The inflow habitats we studied <br />were shallow (<2 m) floodplain zones, typically turbid, and adjacent to river flow. These areas <br />were greatly influenced by changes in reservoir elevation and river stage. Sampling occurred <br />between RM 48 and 56 in the San Juan Arm and between Imperial Rapids and Farley Canyon <br />(RM 200 to 163) on the Colorado River Arm of the reservoir (Figure 2). River turbidity only <br />extended to Hite Marina on the Colorado River arm and downstream to Copper Canyon on the <br />San Juan Arm. <br /> <br />Sampling Techniques - The following 7 sampling methods were used: <br /> <br />Trammel Nets. Two mesh sizes and lengths of trammel nets were used at all locations: Small- <br />meshed trammel nets (1.3 by 15- m long) were constructed of multifilament twine with 25-cm <br />bar meshed outer panels and a 1.2-cm bar meshed inner panel, large-meshed trammel nets (1.8 m <br />by 30 to 45 m in length) had 30-cm bar meshed outer panels and a 3.7-cm bar meshed inner <br />panel. Trammel nets were typically set perpendicular to shore at depths <5 m. Nets were set <br />prior to sunset and checked or pulled in early morning. Catch per unit effort (CPUE) was <br />expressed as fish captured per 100 m2 of net fished (fish/1 00 m2) per net night. <br /> <br />Electrojishing. An electrofishing boat, equipped with a 5,000-watt generator and a Colfelt RF- <br />10 shocker, was used to sample shoreline habitats. Generally, all shocking was done after dark <br />except in flowing portions ofthe Colorado River which were sampled during the day for safety <br />reasons. Shocking normally started an hour after dusk and fish were collected by two netters. <br />Shocking effort was divided into 3, 15-minute (900 sec) shocking periods. CPUE was expressed <br /> <br />3 <br />
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