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RIN 7.4.1 What is the desired range of seasonal and annual flow dynamics associated with <br />powerplant operations, BHBFs, and habitat maintenance flows, or other flows that meet GCDAMP <br />goals and objectives? <br />EIN 2.1.1 How does the abundance and distribution of all size classes of HBC in the LCR and <br />mainstem change in response to an experiment performed under the Record of Decision, <br />unanticipated event, or other management action? <br />EIN 2.1.2 How does the year class strength of HBC (51 - 150 mm) in the LCR and mainstem <br />change in response to an experiment performed under the Record of Decision, unanticipated event, <br />or other management action? <br />EIN 2.4.1 How does the abundance and distribution of nonnative predatory fish species and their <br />impacts on native fish species in the Colorado River ecosystem change in response to an experiment <br />performed under the Record of Decision, unanticipated event, or other management action? <br />EIN 2.6.1 How. does the abundance, distribution, recruitment and mortality of flannelmouth sucker, <br />bluehead sucker and speckled dace populations in the Colorado River ecosystem change in response <br />to an experiment performed under the Record of Decision, unanticipated event, or other <br />management action? <br />SIN 8.5.4 What is the role of turbidity and how can it be managed to achieve biological objectives? <br />Methods and Tasks <br />The nearshore ecology study will incorporate findings from ongoing studies and develop new sampling <br />and analytical approaches that examine the effects of the March 2008 high -flow experiment on <br />nearshore habitats and address the effects of modified low fluctuating flows (MLFF), including <br />September — October fall steady experimental flows (FSEF), on juvenile HBC and other native fishes. <br />The specific methods that the cooperator will use to address these issues are: <br />1. Investigate sampling methods to estimate fish habitat use, growth, and survival. Estimation of <br />juvenile abundance, survival rate, growth rate, and habitat use is fundamental to resolving <br />uncertainties in the conceptual model and the two key research questions outlined and identified <br />above. We propose sampling trips in late July and late August to characterize abundance, habitat <br />use, growth, and survival rate of juvenile fish over the summer under MLFF flow fluctuations. <br />These trips would be followed by sampling trips in early September and late October to <br />characterize juvenile fish responses during the MLFF -FSEF transition, and FSEF period. <br />Differences in abundance in each habitat type, between each sampling trips would be used to <br />estimate habitat specific, reach -wide survival rates across flow events. We propose two basic <br />sampling approaches for estimating these characteristics: (1) reach -wide abundance estimation <br />(RWAE); and (2) robust - design mark - recapture (RDMR) at replicate sites. <br />2. Site selection. We will use existing data and models from the GCMRC physical science program <br />to quantify habitat availability over the study reach that contains the RDMR sites, habitat <br />availability within the sites, and how habitat changes with flow. The existing GCMRC shoreline <br />18 <br />