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Last modified
8/11/2009 11:34:21 AM
Creation date
5/22/2009 12:31:02 PM
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UCREFRP
UCREFRP Catalog Number
8105
Author
Haines, G. B., D. W. Beyers and T. Modde.
Title
Estimation of Winter Survival, Movement and Dispersal of Young Colorado Squawfish in the Green River, Utah.
USFW Year
1998.
USFW - Doc Type
Recovery Program Project 36,
Copyright Material
YES
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<br />SUBADULT HUMPBACK CHUB IN THE COLORADO RIVER <br /> <br />281 <br /> <br />Talus Cobble <br />Change in angle of repose and substrate size Homogeneous angle of repose and substrate <br />result in less cover at higher Q result in no cover change at higher Q <br /> <br /> <br />Qhigh <br /> <br />Qlow <br /> <br /> <br />- <br /> <br />Q <br />D------<58oc::> <br /> <br />Figure 9. Channel cross section demonstrating difference of how cover changes with discharge between geologically dependent and <br />independent shoreline types <br /> <br />~ <br /> <br />at all discharges encountered in this study (Figure 9). However, this relationship must be sinusoidal over <br />a larger range of discharge, because cobble, sand and vegetation will be exposed at some discharge lower <br />and inundated at some discharge higher than those observed in this study. <br />Although food abundance was not considered in this study, regulation by Glen Canyon Dam has <br />altered food availability and the food web dynamics in the Colorado River through Grand Canyon (Blinn <br />and Cole, 1991; Angradi, 1994). Glen Canyon dam traps allochthonous debris, thereby shifting the food <br />base from allochthonous to primarily autochthonous material. Such alterations may alter or limit food <br />availability in channel margins. However, vegetated shorelines may provide allochthonous debris from <br />riparian vegetation and, macroinvertebrates may be associated with such inputs. Fish may select <br />vegetation for this reason only, or more likely, they may be attracted to a combination of habitat <br />conditions that include greater food availability and specific physical conditions. <br />Loss of historic habitat. Another possible explanation for subadult humpback chub occurring along <br />vegetated shorelines rather than natural shoreline types is that certain habitat types have been lost with <br />the onset of flow regulation. Because flow and sediment transport regimes in the Colorado River through <br />Grand Canyon have been altered, sand deposits are less extensive and structurally more simple (less <br />sinuous perimeter and less complex bedforms) than those that occurred in the pre-dam era (Graf et al., <br />1987; Schmidt and Rubin, 1995). Sand deposits may have historically provided complex, sinuous shoreline <br />habitat, such as backwater habitat, that no longer exists or is currently infrequent and ephemeral. <br />Shoreline complexity in sand deposits (e.g. backwater habitat) is known to provide lower depths and <br />velocities for small fish and greater protection from predators (Tyus, 1991, 1991; Jurajda, 1995). The few <br />backwaters that are permanent in Grand Canyon can have very high densities of young native fish, but <br />fish presence in backwaters depends on high turbidity conditions (personal observation; Arizona Game <br />and Fish Department, 1994; Valdez and Ryel, 1995). <br /> <br />, <br />. <br /> <br />.. <br /> <br />Implications of flow regulation on survival of subadult humphack chub <br /> <br />When compounded with other changes in the river ecosystem, decreased habitat quality may limit <br />survival of subadult humpback chub in Grand Canyon. In addition to a general reduction in physical <br />habitat quality, the dam has altered water temperature. Historically, temperatures ranged from 2 to 180C. <br />The Colorado River temperature now averages from 9 to 110C at the LCR (US Department of Interior, <br />Bureau of Reclamation, 1995; Valdez and Ryel, 1995). Consequently, growth, reproduction and survival <br />of native fish have almost certainly been affected. Bulkley et al. (1981) showed extreme compromises in <br />swimming abilities and growth rates of humpback chub in temperatures ranging from 5 to 150C. In <br />response to these changes in the wild, young fish may be limited to very different environments where they <br />expend less energy to compensate for reduced growth efficiency imposed by suboptimal temperatures. For <br />example, subadult humpback chub may be forced to occupy a portion of the channel margin nearer to <br />shore, which has more cover and refuge from high velocities to reduce energy expenditure, or young fish <br />may shift to naturalized vegetated shorelines that consistently provide these conditions at a range of <br />discharges. <br /> <br />@ 1998 John Wiley & Sons, Ltd. <br /> <br />Regul. Rivers: Res. Mgmt. 14: 267-284 (1998) <br />
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