Winter Steelhead Monitoring in Western Oregon: How Do You Get from Redds to Fish?

The use of redds as a metric for monitoring salmonid spawner abundance is well established.  However, monitoring based on estimated redd abundance creates a disconnect with harvest management and population viability assessments, which are typically based on numbers of fish.  From methodology development work conducted by ODFW in the late 90’s a linear regression was developed to predict total adult winter steelhead from redd counts along the Oregon Coast.  Variation in observed redd to fish conversions suggested temporal and spatial differences.  Thus, use of average or modeled conversion methods could lead to inaccurate annual estimates of winter steelhead spawners over such a broad geographic scale.  Developing multiple calibration sites that can provide annual estimates of redd to fish conversions across the monitoring area could address this issue. Beginning in 2014, assessments of adult winter steelhead per redd rates in four different sites along the Oregon Coast and Oregon portion of the Lower Columbia was initiated.  Two additional Oregon coastal sites have been monitored separately for the past several years.  The following presentation summarizes the results of that monitoring and explores the factors influencing the spatial and temporal differences in redd to fish rates.