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• 11. [Article] Evaluation of a Sampling Approach to Monitor the Status of Great Basin Redband Trout in Southeastern Oregon (2007 – 2009) Information Reports number 2010-02

  Abstract -- The summer 2009 field season marked the completion of the third of a six year sampling effort to assess the distribution and abundance of redband trout (Oncorhynchus mykiss newberrii) in the ...

  Citation × Citation Citation Abstract Copy Title: Evaluation of a Sampling Approach to Monitor the Status of Great Basin Redband Trout in Southeastern Oregon (2007 – 2009) Information Reports number 2010-02 Abstract -- The summer 2009 field season marked the completion of the third of a six year sampling effort to assess the distribution and abundance of redband trout (Oncorhynchus mykiss newberrii) in the six interior basins of Oregon’s high desert: Catlow Valley, Chewaucan, Fort Rock, Goose Lake, Malheur Lakes, and Warner Valley Species Management Units (SMUs). Across all sampling years, sites were randomly selected using Generalized Random Tessellation Stratified (GRTS) design, which provides a random spatially balanced sample allowing for statistically rigorous evaluation of status, trend and distribution at multiple spatial scales. A total of 700 site surveys were conducted over the course of the study covering nearly 2% of the entire 2,420 km sampling frame. Abundance of age-1+ redband trout at the SMU level has remained relatively stable throughout the course of this study but has decreased since intensively sampled in 1999. Estimates of landscape-wide abundance of age-1+ redband trout were of similar magnitude and had comparable precision across all three study years, averaging 878,000 + 16%. However, abundance at the SMU and population (stratum) level showed substantial variation, both spatially and inter-annually. Fish densities (fish/m) sampled at sites visited annually (2007-2009) showed significant differences between years, specifically between 2007 and 2009 in the Chewaucan and Fort Rock SMUs. Target levels of relative precision were achieved twice at the SMU level, and in approximately half of the strata. Increasing the number of sites sampled to increase precision is not likely, given limited funding. Yet, the current study design falls short of providing precise information to develop conservation management plans. Alternative sampling designs that would maximize data acquisition at the population level, while allowing for estimates of yearly variation were explored and suggested. Title: Evaluation of a Sampling Approach to Monitor the Status of Great Basin Redband Trout in Southeastern Oregon (2007 – 2009) Information Reports number 2010-02 Abstract -- The summer 2009 field season marked the completion of the third of a six year sampling effort to assess the distribution and abundance of redband trout (Oncorhynchus mykiss newberrii) in the six interior basins of Oregon’s high desert: Catlow Valley, Chewaucan, Fort Rock, Goose Lake, Malheur Lakes, and Warner Valley Species Management Units (SMUs). Across all sampling years, sites were randomly selected using Generalized Random Tessellation Stratified (GRTS) design, which provides a random spatially balanced sample allowing for statistically rigorous evaluation of status, trend and distribution at multiple spatial scales. A total of 700 site surveys were conducted over the course of the study covering nearly 2% of the entire 2,420 km sampling frame. Abundance of age-1+ redband trout at the SMU level has remained relatively stable throughout the course of this study but has decreased since intensively sampled in 1999. Estimates of landscape-wide abundance of age-1+ redband trout were of similar magnitude and had comparable precision across all three study years, averaging 878,000 + 16%. However, abundance at the SMU and population (stratum) level showed substantial variation, both spatially and inter-annually. Fish densities (fish/m) sampled at sites visited annually (2007-2009) showed significant differences between years, specifically between 2007 and 2009 in the Chewaucan and Fort Rock SMUs. Target levels of relative precision were achieved twice at the SMU level, and in approximately half of the strata. Increasing the number of sites sampled to increase precision is not likely, given limited funding. Yet, the current study design falls short of providing precise information to develop conservation management plans. Alternative sampling designs that would maximize data acquisition at the population level, while allowing for estimates of yearly variation were explored and suggested. Close