Matt Nahorniak, SFR
CHaMP’s sampling was designed to annually estimate population-scale status and trends for all key habitat metrics. Each CHaMP watershed went through a design process to select sites in an unbiased, stratified-random, and spatially balanced fashion that allows metric estimation for an entire watershed.
In most CHaMP watersheds designs balance local sampling needs with the CHaMP goal to produce regionally comparable metric estimates. For example, the Entiat, Yankee Fork, and Tucannon designs embedded effectiveness monitoring sampling with watershed-scale status and trend sampling. Similarly, the Grande Ronde needed a unique design to estimate status and trends of habitat for both Steelhead and Chinook, which have different, overlapping extents.
Most designs balanced sampling across smaller ‘source’, pool-riffle dominated ‘transport’, and low gradient, ‘depositional’ reaches. In large watersheds with a mix of public and private landowners, designs
are also stratified by ownership type to avoid biased sampling of public lands. CHaMP achieves spatial balance via use of a Generalized Random Tessellation Stratified (GRTS) sample selection algorithm, and designs are reviewed and updated annually as needed. The regionally consistent sampling design, collection protocol, and metrics allows investigation of the sources of metric variation across the interior Columbia. This ‘variance decomposition’ provides insight to how metrics vary across the landscape and through time.
Findings and Uses
CHaMP’s sampling design structure provides:
- Flexibility that accommodates sampling changes without complete loss of long-term status and trend metric estimations.
- Unbiased status and trend metric estimation for individual populations, across populations , and at sub-watershed scales, including impact assessment of restoration
- A spatially diverse set of sites that can be repurposed as reference sites, or supplemented with fish and other sampling.
- The ability to separate metric variance across space and time