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8/11/2009 11:32:58 AM
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UCREFRP
UCREFRP Catalog Number
9702
Author
Petersen, J.H., and C.P. Paukert.
Title
Development of a bioenergetics model for humpback chub and evaluation of water temperature changes in the Grand Canyon, Colorado River.
USFW Year
2005.
USFW - Doc Type
Transactions of the American Fisheries Society
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970 <br />PETERSEN AND PAUKERT <br />TABLE 6-Predicted growth and consumption for juvenile and subadult humpback chub in the Colorado River below <br />Glen Canyon Dam based on a bioenergetics model and four temperature and food scenarios. Model fish were grown <br />for 1 year. The start size for juvenile fish was 4 g; for Subadult was 115 g. Food availability (p) was 0.65 except for <br />one simulation in which it was assumed to have increased to 0.75. <br />Temperature and food scenario <br />Predicted <br />response (g) <br />Increased Increased <br />Pre dam Post dam temperature temperature <br />temperatures, temperatures, (May-Oct), (May-Oct), <br />p=0.65 p=0.65 p=0.65 p=0.75 <br />Final size 22 <br />Consumption 123 <br />Final size 124 <br />Consumption 709 <br />Juvenile <br />12 16 24 <br />48 76 106 <br />Subadult <br />123 124 158 <br />378 516 657 <br />p values and the potential response of growth rates <br />j to various conditions. Stronger corroboration test- <br />ing might be done by comparing feeding rates from <br />the field with model-predicted feeding rates; how- <br />ever, such data are difficult to obtain, are often <br />highly variable, and depend themselves on various <br />assumptions about times of feeding, temperature, <br />prey size, and other factors (Adams and Breck <br />1990). We were able to simulate observed growth <br />rates with reasonable p values at a broad range of <br />temperatures and in two habitats where humpback <br />chub occur (the Colorado and Little Colorado riv- <br />ers), so the model and parameter estimates should <br />be a useful tool for scientists and managers. <br />Temperature Control Device Implications <br />Water temperature has been identified as a pos- <br />sible cause of declines of native fishes in the Grand <br />Canyon (Minckley 1991), and warmer water tem- <br />peratures have been shown to improve the con- <br />dition and swimming ability and to increase the <br />growth rate of native fishes (Clarkson and Childs <br />2000; Meretsky et al. 2000; Ward et al. 2002). The <br />implementation of a TCD on Glen Canyon Dam <br />that will increase water temperatures 5-10°C in <br />the Colorado River may also increase the growth <br />rate of humpback chub if food availability increas- <br />es simultaneously. Our simulations suggested that <br />humpback chub growth rates were relatively con- <br />stant at water temperatures between 5 and 25°C if <br />food availability was constant at moderate levels. <br />Higher growth rates were predicted at increased <br />water temperature coupled with increased food <br />availability. Water temperature can strongly influ- <br />ence consumption by fish, and individuals cannot <br />feed at the same rate at low temperatures as they <br />can at higher temperatures. Consumption typically <br />peaks at an optimum temperature but declines <br />drastically above this optimum temperature (Jo- <br />bling 1994). Therefore, a ration that produces pos- <br />itive growth at low temperatures is not likely to <br />produce similar growth at high temperatures, and <br />growth rate can decline with increased temperature <br />and no concomitant change in ration. An evalua- <br />tion of any management action for humpback chub <br />that alters temperature must take into account prey <br />availability and consumption across the range of <br />expected temperatures. <br />Temperature changes following implementation <br />of a TCD will likely cause complex changes at <br />several trophic levels in the lower Colorado River, <br />and these changes should be closely monitored <br />(Poff et al. 1997). In particular, the abundance and <br />species composition of invertebrates, the primary <br />food base for fishes in the Grand Canyon (Valdez <br />and Ryel 1995), should be monitored if a TCD is <br />implemented. In other river systems, the response <br />of invertebrate populations to increased tempera- <br />tures has been mixed. An increase in water tem- <br />perature of 2YC caused a decrease in the densities <br />of invertebrates in a Canadian stream experiment, <br />although growth rate of the invertebrates increased <br />(Hogg and Williams 1996). At Flaming Gorge <br />Dam in Utah, an increase of summer water tem- <br />perature from 6 to 12°C did not change the taxa <br />richness of invertebrates (Vinson 2001). Com- <br />pared with other unregulated rivers in the region, <br />the Colorado River in Grand Canyon has had a <br />relatively depauperate invertebrate community <br />following closure of Glen Canyon Dam (Stevens <br />et al. 1997), suggesting the cool, stenothermal re- <br />gime may have decreased species diversity and <br />abundance. Although water temperature may be <br />the most important variable in determining local <br />invertebrate community dynamics in streams <br />(Vannote and Sweeney 1980), other factors such <br />as turbidity ant <br />be influential (i <br />1980). Tempera <br />production rate; <br />Colorado Rivet <br />on humpback c <br />Temperature <br />sized causes of <br />River, with flov <br />ductions also it <br />Abundant nonn <br />now, channel c: <br />carp, rainbow t <br />most importan <br />(Minckley 1991 <br />may cause incr( <br />creased main-st <br />that currently <br />(Clarkson ands <br />2001). Warmer <br />also increase 1 <br />striped bass M( <br />Colorado River <br />sibly increasing <br />other native fis <br />The most proxii <br />nonnative pred: <br />mode of distrit <br />Large brown tr4 <br />adult humpbacl <br />sonal communi <br />tolerant than at <br />peratures and al <br />conditions (R( <br />1999), commor <br />River. <br />The impacts <br />the growth rate: <br />and brown trou <br />small humpbac <br />ators. The size <br />bow trout cons <br />size range (W: <br />1999), so faste <br />ration of time t. <br />ator. With incre <br />food availabilit <br />"window of <br />shorten if the ; <br />chub increased. <br />depends upon <br />and their prey, <br />temperature re€ <br />some estimates
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