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POWER TO DETECT REGIONAL TRENDS IN PHYSICAL HABITAT
Citation:
Kaufmann, P R. AND D P. Larsen. POWER TO DETECT REGIONAL TRENDS IN PHYSICAL HABITAT. Presented at Oregon Chapter American Fisheries Society, Eugene, OR, February 28, 2003.
Description:
The condition of stream habitat draws considerable attention concerning the protection and recovery of salmonid populations in the West. Habitat degradation continues and substantial sums of money are spent on habitat restoration. However, aided by uncertainty concerning the adequacy of field methods for quantifying habitat, there is to date no established monitoring design and field approach to track regional trends in habitat condition. Using survey data collected throughout the Northwestern US by the Environmental Monitoring and Assessment Program (EMAP), we quantified sources of variability to determine the adequacy of several commonly-used habitat measures in a regional trend monitoring context. We evaluated regional, annual, and within-season components of variation in measures of sediment %fines, residual pool depth, woody debris volume, and riparian canopy cover. Depending upon the habitat metric, we estimate that, with a probability sample of 50 stream sites visited once per year, a monitoring program would have 80% likelihood (power) to detect a rather subtle trend of 1-2% per year within 8-20 years, if such a trend is present. This is good news, but it underscores the need to put into place long-term monitoring programs, if we are to detect these trends in timely fashion.