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-' , Introduction A recent evaluation of the Upper Colorado River Fisheries Recovery Program (Stanford 1994) concluded that a standardized sampling program for monitoring aquatic invertebrates should be implemented. Primary issues outlined by Stanford were the lack of information on th~ distribution and abundance patterns of zoobenthos communities. the need to identify invertebrate taxa and habitat types with a strong dependence on flow characteristics. and the need to develop rapid assays to detect ifinvertebrate production might be limiting endangered fish populations. An understanding of where and why changes in invertebrate communities occur will improve our ability to predict how downstream invertebrate communities may change in relation to the hydrologic regime. We also need to evaluate inter-habitat variation in invertebrate populations. Certain habitats. e.g., backwaters. are thought to support higher production of invertebrates (zoobenthos and zooplankton) than others, e.g.; main channel runs (Stanford 1994). Different habitat types are also thought to exhibit variable sensitivity to discharge (Stanford 1994). The design and implementation of a monitoring program should be an iterative process. Sampling locations and methods should be added, removed. or modified as results are evaluated annually. The sampling program outlined here should be viewed more as a starting point rather than as long-term protocols. The initial emphasis of the project should be to delineate sampling locations and describe both the inter- and intrahabitat variability of invertebrate communities within and among sampling reaches. This initial data from this project will. allow us to design a custom fit sampling program for individual reaches and habitats and will result in a better final monitoring project. ffitimately the key to making this monitoring project useful and cost-effecting 2