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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 />