Linking altered physical processes with fish life histories and habitat references to guide restoration planning in the San Rafael River, Utah

Authors: Brian Laub, Phaedra Budy, Justin Jimenez

Year: 2012 (xliv)

Abstract

Habitat loss and population fragmentation are two of the main threats to native fish species in the Green and Colorado River basins. Habitat restoration within tributaries could increase habitat availability for native species and provide connectivity between tributary and mainstem populations. However, restoration goals should be based on an understanding of physical processes operating within the river system, so that restoration actions to improve habitat are sustainable within the current hydrologic and sediment regimes. The San Rafael River, a tributary of the Green River in east-central Utah, is being targeted for restoration because it maintains populations of three native fish species of management concern (collectively, the three species). Alteration of the flow regime and establishment of non-native woody vegetation (primarily Tamarix) along the lower San Rafael have led to a narrowing and simplification of the river channel and a loss of channel features such as point and gravel bars and floodplain backwaters. The lower section of the river is primarily a stable, low-velocity, sandy run or glide habitat. Life history requirements of the three species are not well matched to current conditions in the river, and surveys have demonstrated low population abundance of the three species throughout the lower San Rafael. Complete restoration of a wide, complex channel system throughout the entire lower San Rafael is unlikely given the current hydrologic regime. However, using the life history requirements of the native species and the continuous spatial configuration of fish habitat, it may be possible to target restoration actions at specific locations to aid physical processes in maintaining suitable habitat conditions (e.g., Tamarix removal at tributary junctions where the river is likely to be less stable and where coarse sediment is provided). In the meantime, ensuring connectivity to upstream and mainstem populations should be a management priority.