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<br />RIVER RESEARCH AND APPLICATiONS
<br />
<br />River Res, Appfic, 22: 1125-1142 (2006)
<br />
<br />Published online in Wiley InterScience
<br />(www.interscience.wiley.com). DOl: IO.l002/rra,967
<br />
<br />A PHYSICAL HABITAT MODEL FOR PREDICTING THE EFFECTS OF FLOW
<br />FLUCTUATIONS IN NURSERY HABITATS OF THE ENDANGERED
<br />COLORADO PIKEMINNOW (PTYCHOCHEILUS LUCIUS) T
<br />
<br />TAMARA C. GRAND,a* STEVEN F. RAILSBACK,b JOHN W. HAYSE" and KIRK E. LAGORY"
<br />
<br />. J08 Roe Drive, Port Mood\,. British Columbia V3H 31\-18, emU/da
<br />b Lang, Railsback and Associates, An'ata, California, USA
<br />C Environmental Assessment Division, Argonne National Laboratory, Argonne, Illinois, USA
<br />
<br />ABSTRACT
<br />
<br />Larval and juvenile Colorado pikeminnow (Ptychocheilus lucius) use shallow, low-velocity, channel-margin areas (backwaters)
<br />as nursery habitats,Jt is hypothesized that within-day flow fluctuations caused by hydropower operations can directly affect the
<br />suitability of such habitats by altering water temperature and habitat geometry, Despite the importance of backwaters to juvenile
<br />fishes, there is a lack of established approaches for modelling how river management affects these habitats, Here, we describe a
<br />physical habitat model that predicts the etTects of mainstem flow variation on backwater temperature, geometry ,md invertebrate
<br />availability, We specifically modelled these effects on habitat in a portion of the Green River in Utah below !-laming Gorge Dam.
<br />The overall model combines a cell-based model of backwater geometry, a pond-based temperature model and a model of
<br />invertebrate production, Results from a series of simulations suggest that the most important biological effects of within-day
<br />flow fluctuations are likely to be those associated with the availability of invertebrate prey including (1) minimum wetted area,
<br />(2) the proportion of the backwater's volume exchanged with the mainstem, and, to a lesser degree, (3) backwater temperature.
<br />Taken together, such effects could have important implications for the growth and survival of juvenile fish when flow fluctuations
<br />are sufficiently large, Copyright '&) 2006 John Wiley & Sons, Ltd,
<br />
<br />KEY WORDS: backwater habitats; flow fluctuations; simulation modelling; Colorado pikeminnow; Green River; Flaming Gorge Dam;
<br />temperature; invertebrate production
<br />
<br />Received 12 AI/gust 2005; Revised 1 May 2006; Accepted 5 June 2006
<br />
<br />INTRODUCTION
<br />
<br />Short-term flow fluctuations can occur frequently in regulated rivers. Temporal variation in the demand for
<br />hydroelectric power can result in mainstem flows that change not only daily, but from hour to hour. While much
<br />attention has been focused on the effects of flow fluctuations on fish inhabiting the main channels oflarge, regulated
<br />rivers (e.g. Cushman, 1985; McKinney et aI., 2001), few researchers have addressed the effects of flow variability
<br />on shallow, low velocity channel-margin habitats (backwaters) and the fish that inhabit them (but see Minckley
<br />et al., 2003). Such backwaters are frequently used as nursery habitat by juvenile fish (Tyus and Haines, 1991;
<br />Minckley et al., 2003; Gutreuter, 2004), In the Colorado River basin, backwaters provide important nursery habitat
<br />for young of the year native fish, including the endangered Colorado pikeminnow (Ptychocheilus Iudus), and have
<br />become a major focus of population recovery efforts (Mincldey et aI., 2003).
<br />Colorado pikeminnow larvae emerge from spawning gravels in early summer, following the peak of spring snow-
<br />melt runoff, Larvae drift downstream to alluvial portions of the river and enter channel-margin backwaters where
<br />they remain for their first year. During this period, flows tend to be relatively low and stable. Because backwater
<br />habitats are somewhat isolated from the main channel, they tend to be warmer and more productive than main
<br />
<br />*COlTespondence to: T. C, Grand, 108 Roe Dlive, Port Moody, British Columbia V3H 3M8. Canada, E-mail: tgrand@sfu.ca
<br />tThe submitted manuscl;pt was created, in part, by the University of Chicago as Operator of Argonne Natiolllll Laboratory ('Argonne') under
<br />Contract No, W-31-l 09-ENG-38 with the V,S, Department of Energy, The U.S, Government retains for itself, ,rod others acting on its behalf, a
<br />paid-up. nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, dish'ibme copies to the public and
<br />perfOlm publicly and display publicly, by or on be,half of the Government.
<br />
<br />Copyright ((;) 2006 John Wiley & Sons, Ltd,
<br />
<br />~jWILEY
<br />InterScience"
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