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Assess Salmonids in the Asotin Creek Watershed: 2006 Annual Report

Category: Fish/Shellfish Research and Management - Fish/Shellfish Research

Date Published: March 30, 2007

Number of Pages: 41

Author(s): Kent Mayer, Mark Schuck and Darin Hathaway

The goal of this project is to assess the status of anadromous salmonid populations in Asotin Creek. This research, monitoring and evaluation project provides estimates of abundance, productivity, survival rates, and temporal and spatial distribution of ESA-listed species: Summer steelhead (Oncorhynchus mykiss) and spring Chinook salmon (O. tshawytscha). Adult salmonids entering Asotin Creek to spawn were enumerated using a floating, resistance board weir. The juvenile migrant population was estimated using a rotary screw trap. Four-hundred and seventy seven (477) adult steelhead were captured in 2006 (the second season of adult trapping in Asotin Creek), resulting in population estimate of 555 adults, spawning in 46 kilometers of habitat above the trapping site. The juvenile steelhead population was estimated at 36,568 (95% CI = 30,822 – 43,436 juveniles) from the combined spring and fall out-migrations in the 2006 calendar year. In addition, 1,035 juvenile spring Chinook salmon were captured in 2006, resulting in a population estimate of 2,358 individuals. Passive integrated transponder tagging of out-migrating juvenile steelhead in 2006 indicted that 3.4% of the age 1 fish were detected at a mainstem dam during the outmigration year, while 78.0% and 84.3% of the age 2 and age 3 fish were detected, respectively. This report also provides a multi-year data comparison of project data collected to date: two years of adult data from 2005 and 2006, and three years of juvenile data from 2004, 2005 and 2006. Data suggests that the Asotin Creek summer steelhead – above eight mainstem dams on the Snake and Columbia Rivers – is a productive, naturally sustaining population of the Snake River steelhead ESU. The Asotin Creek project may provide data to assess the population response to habitat recovery actions in the subbasin. We also believe that Asotin Creek is an important reference stream for ESA-listed steelhead populations, because it may be the only unsupplemented, eastern Washington steelhead population that can provide data to evaluate supplementation programs on the eastside of the Columbia River basin.