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Project 6—Support and Enhancement of Ecosystem Modeling Efforts <br />(1112.P1.10) <br />Need for Project <br />While a variety of experimental management policies have been implemented in recent years, analysis <br />and communication of results and responses of indicators to policies have not been completed. More <br />complete analysis and subsequent communication of the results of analysis (including modeling) will <br />allow more effective selection of further experimental tests. For example, the LSSF flow experiment of <br />summer 2000 was not fully evaluated until 2008, and likewise there have not been definitive reviews of <br />all high -flow experimental results (1996 to 2008) or the effects of mechanical removal of nonnative fish, <br />although the synthesis of flow tests and nonnative control analyses are now forthcoming. Such analyses <br />have been hampered by confounding of multiple factors in causing changes (for example, temperature <br />changes have made it hard to interpret fish responses to mechanical removal). Modeling tools provided <br />by the Senior Ecologist (Walters) can help to at least clarify alternative hypotheses about the possible <br />roles and relative importance of the factors. <br />Additional advancement of the flow and sediment elements of the existing GCEM is also planned as an <br />additional element of the new Integrated Flow, Sediment, and Temperature Modeling research project <br />(Wright and others in collaboration with Korman and Walters) as a further means of assessing fine <br />sediment dynamics associated with various stakeholder planning needs and associated tasks tied to <br />developing desired future conditions for GCDAMP goals. <br />Strategic Science Questions <br />The ecological modeling efforts will be directed at addressing priority AMWG questions, SSQs, and <br />additional science questions (SAs) - provided by the Science Advisors (SA) in the integrated modeling <br />efforts, as follows: <br />Abundance trends of rainbow trout in the Lees Ferry reach: <br />SSQ 1 -4 Can long -term decreases in abundance of rainbow trout in Marble and eastern Grand <br />Canyons be sustained with a reduced level of effort of mechanical removal or will recolonization <br />from tributaries and from downstream and upstream of the removal reach require that mechanical <br />removal be an ongoing management action? <br />This question also applies to future removal programs targeting other nonnative species. <br />SSQ 1 -8 How can native and nonnative fishes best be monitored while minimizing impacts from <br />capture and handling or sampling? <br />Abundance trends in native fish below the Lees Ferry reach: <br />SSQ 1 -1 To what extent are adult populations of native fish controlled by production of young fish <br />from tributaries, spawning and incubation in the mainstem, survival of young -of -year and juvenile <br />stages in the mainstem, or by changes in growth and maturation in the adult population as influenced <br />by mainstem conditions? <br />33 <br />