Keeping an eye on redband trout in 28,000 miles of high desert

What is the Problem?

Redband trout (Oncorhynchus mykiss newberrii) are an important indicator of stream health and form the basis of several popular fisheries throughout Oregon. The species is so widely distributed that keeping track of its status has proved problematic for fishery managers faced with limited resources. In the Great Basin (southeast Oregon), redband trout occupy a landscape characterized by spatial and temporal variability in environmental conditions that likely influences their abundance. Developing long-term monitoring protocols and effective conservation plans will require an understanding of spatial and temporal variability in abundance of redband trout as well as an understanding of the balance between sampling intensity and precision of empirical data.

 

What are we doing?

NFi staff conducted a six year study to address the following objectives: 1) quantify the abundance and distribution of redband trout at two putative demographic scales in the northern Great Basin and 2) quantify variability in the sampling data to help guide development of conservation and monitoring plans for redband trout in the northern Great Basin.

 

Why?

This information will be primarily be used to determine the feasibility of monitoring the status of the species. Additionally, the study will provide insight into the current health of populations in this region, their population structure, and their genetic "fitness".

 

Results

Our observations suggest that this species is currently widely distributed in the Northern Great Basin. The abundance of redband trout varied from 1,716 to 191,690 among populations and from 17,709 to 566,514 among SMUs during the six years. Abundance was generally stable within populations and SMUs over the six-year study; however, inter-annual variation was observed in some populations and SMUs. We predicted that about 16 and 71 sample sites would need to be sampled at the population and SMU levels, respectively, to achieve desired levels of precision of abundance estimates (i.e., ≤ 80% and ≤ 40% relative confidence index at the population and SMU levels, respectively). Sampling intensities of > 60 and 100 sample sites at the population and SMU levels, respectively, result in little benefit in our ability to detect change in redband trout density using the current approach. Additionally, variability in point estimates of redband trout density did not decrease substantially at sampling intensities greater than about 20 sample sites at the population and SMU levels. For more detailed results, please download the final report (here)

Who to contact?

Mike Meeuwig
Shaun Clements

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