8061

• UCREFRP Catalog Number: 8061
• Author: Mueller, G. and P. Marsh.
• Title: Post-Stocking Dispersal, Habitat Use, and Behavioral Acclimation of Juvenile Razorback Suckers ‎(
• USFW Year: 1998.
• Copyright Material: NO

- 50
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>- 40
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::s 30
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u. 20
10

70
60

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.<10 m
810-50 m
.>50 m

lake Mohave
(N=601

lake Powell
(N=1591

Figure 4. Percentage of razorback sucker detection less than 10, 10 to 50, and greater than
50 m from shore in lakes Mohave and Powell, May through July 1997.

inundated hundreds of hectares of flooded tamarisk which was impossible to monitor effectively.
Submerged vegetation absorbed the sonic signal significantly reducing the signal range in some
cases <50 m. During this period the water falls was also inundated and surveys were extended
upstream (20 kIn) to Slickhom Rapids (RKI06) and during the week of August 12, two boat
crews searched the entire 106 kIn reach between the confluence of the San Juan and Colorado
rivers (RK 0) to Slickhom Rapids (RK 106). Although the search effort was extensive, no
additional fish were found.

Cover was an important habitat component and represented >50% of our observations. It
appears cover was being used for concealment and the type used varied, dependent upon its
availability. Fish utilized three types in Lake Mohave; submerged tamarisk (Tamarix
pentandra), large rocks and ledges, and submergent vegetation (Najas or Potamogeton spp.).
Fish were most often (48-86%) found in flooded tamarisk (Figure 5). The second most
prevalent cover type where juvenile suckers were found in Lake MOhave was submergent
vegetation (40%) and the last cover type used was rock ledges or rubble (12-14%). Similar cover
types were found in Lake Powell with the exception of emergent vegetation.

Range

Lake Powell We detected 23 of the 28 fish released at Castle Creek Canyon (Table 1). The
initial movement of some fish was pronounced, and generally uplake (RK >73) and only two
ventured downstream. The maximum distance fish were detected from the release site was 4.6
kIn upstream and 2.7 kIn downstream.

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