Investigation of Ecological Interactions in Small Complex Habitats for use in Refugia Design in Regulated Rivers.
Habitat improvement and refugia projects for a number of State or federally protected fish species such as the Rio Grande silvery minnow, _Hybognathus amarus_, are being considered. These projects seek to mitigate negative effects of Reclamation operations without interrupting water delivery. Effective projects will ultimately depend upon accurate and reproducible understanding of ecological services required by these species. Because many fluvial species use large spatial areas over the course of their life-cycle, an important question is:
* Can these services be obtained in a relatively small area of a refugium?
Success of these projects will ultimately depend on the following questions:
* Do natural populations exist in relatively small areas that can be mimicked by habitat improvement and/or refugia projects?
* What are the crucial ecological interactions in these natural populations that must be re-created in these projects to make them successful?
Need and Benefit
The federally endangered Rio Grande silvery minnow exists in an area of the Middle Rio Grande. Recently, habitat improvements proposed by the Interstate Stream Commission and refugia projects proposed by Senator Pete Domenici have sought to use Middle Rio Grande water in a way that would enhance water conservation, use efficiency, and resource monitoring. These projects may have potential to "free" some water used to meet requirements set forth in Section 7 Consultation (Section 7 of the Endangered Species Act [ESA]) with the U.S. Fish and Wildlife Service (FWS).
Currently, silvery minnows are being bred and reared at the Rio Grande Silvery Minnow Refugium in Albuquerque, New Mexico. The facility uses tanks to rear fish and does not re-create natural ecological conditions found in the Rio Grande.
A common life-history strategy for fish species that inhabit rivers is to move upstream to spawn as adults, then broadcast buoyant or semi-buoyant eggs downstream throughout the watershed (e.g., the federally endangered pallid sturgeon, _Scaphirhynchus albus_, and Rio Grande silvery minnow). This strategy increases the likelihood that some fish will survive in patchy, unpredictable fluvial environments, but movement may be disrupted by dams and irrigation diversions. Consequently, Reclamation is being required by various agencies to mitigate for negative effects of some projects where State and federally protected species use this strategy. It is unknown whether proposed small-scale habitat improvements can be designed adequately to mitigate for losses of species that normally use much larger spatial areas.
If small "natural refuges" exist where silvery minnows occur, then there is potential to provide reproducible ecological interaction information that will assist the success of these projects and allow Reclamation to continue water and power delivery to stakeholders. These natural areas may exist just north of Elephant Butte Reservoir where low-flow conveyance channel becomes unregulated, and reproducible ecological interactions may be at work. Limited sampling has verified the presence of the silvery minnow upstream of this reach, and anecdotal information including aerial photography, interviews with field biologists, and hydrograph records indicate the area is structurally complex, unregulated, and inundated all year.
This scoping proposal will seek to briefly investigate these areas, determine presence/absence of silvery minnows and build upon the findings of these surveys and a literature search to submit a more thorough research proposal that will endeavor to quantify conditions in these areas, and by extension, enhance the likelihood of success projects involving the Interstate Stream Commission and Senator Pete Domenici.
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