Montana Fishery Project
Landscape-scale Effects of Wildfire on Aquatic Systems in the Rocky Mountains of Colorado
April 2008 - July 2010
- Alexander Zale, Principal Investigator
- Edwin Sedell, Student / Post Doc
- Northern Rocky Mountain Science Center
In order to provide information necessary to evaluate the effects of wildfire at the landscape scale, interdisciplinary data concerning physical and biological characteristics of study watersheds will be used to spatially assess the vulnerability of a high elevation landscape to negative consequences of fire. Relationships between current terrestrial and aquatic components of fish habitat and current patterns of fish distribution and abundance will be evaluated. Resulting data will be used to: (1) evaluate the risk of wildfire in watersheds in the study area (Grand County, Colorado), (2) identify watersheds where significant post-fire floods, debris flows, and sediment deposition could have negative effects on aquatic resources, and (3) provide information necessary to identify potential prefire management actions that would reduce or eliminate negative consequences to at-risk aquatic resources (e.g., isolated populations of threatened or endangered species). Methodology 1. Consult with collaborators to identify the most appropriate scale for experimental (sample) units (e.g., watersheds) in the study area (Grand County) and determine the sampling frame. 2. A probability-based sampling methodology will be used to select sample watersheds. 3. In each sample watershed, habitat will be hierarchically classified at the segment, geomorphic reach, and channel-unit scales. 4. In collaboration with scientists in local land-management agencies, relative abundance of fish will be estimated in all pools and cascades in each watershed using electrofishing as the primary means of fish collection. All fish will be measured (total length to the nearest 1 mm) and weighed (nearest 0.1 g). In each stream segment, scale samples for age analyses will be collected from up to five fish in each 10-mm length category. 5. Resulting information will be integrated into interdisciplinary and multi-agency databases (remote-sensed imagery, remote technology (MOTES), watershed modeling tools, and tools to analyze wildfire hazards and to mitigate impacts on people, property, and natural resources). 6. Data analyses will be conducted hierarchically at three spatial scales (watershed scale, within watershed, disturbed-control comparisons). Watershed scale analysis provides the most information about the distribution of aquatic invertebrates and fishes prior to disturbances such as fire. Baseline information on predisturbance habitat conditions and spatial patterns of fish distribution will provide a basis for comparison as the study progresses. The second level of analysis will explore watersheds in individual watershed classes (as defined in the initial stream classification). A third level of analysis will differentiate patterns of fish abundance in treatment and control (burned-unburned) watersheds. Geographic analysis of fish movement and spatial patterns in fish distribution will focus on the identification of geomorphically distinct peaks in fish distribution.