Great Basin Redband Trout Overview

Goose Lake and Warner Lakes SMU's

Great Basin Overview: The summer 2010 field season marked the completion of the fourth 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 basins. In addition, the 2007 and 2010 sampling years complete the population level sampling for the Goose Lake and Warner Lakes SMUs.  A total of 972 site surveys were conducted over the course of the study covering over 2% of the entire 2,420 km sampling frame.  Abundance of age-1+ redband trout at the basin level remained relatively stable during 2007 - 2009. However, 2010 estimates indicate a considerable decline when compared to 2007.  Estimates of landscape-wide abundance were of similar magnitude and had comparable precision across all four study years, averaging 802,000 + 16%.

Goose Lake:

The Goose Lake SMU is comprised of 13 populations, of which 6 exist in California and were not assessed in this study.  The 7 remaining populations were grouped into 5 areas (Drews, Dry, Eastside, W. Goose & Thomas-Bauer).  Landowner participation in these areas allowed for sampling at 73% of sites located on private property - best of any basin. Continued landowner participation is key to furthering our understanding  and conservation of redband trout.  During 2007 and 2010, the Goose Lake SMU was monitored intensively where surveys were completed at a total of 177 sites and 230 sites over the entire study.

Abundance of Goose Lake age-1+ redband trout  were highest in 2007.  Abundance declined by 61% since 2007 and has remained consistently low during the last three years. Abundance of redband trout  likely fluctuates with annual stream flow.  Higher water years preceding 1999 and 2007 may have contributed to higher abundance  in those years. Patchy distribution and low fish densities may be due to habitat quality or a less accurate sample frame.

Warner Lakes:

The Warner Lakes SMU is comprised of 3 populations: Deep, Honey, and Twentymile.  Landowner participation in these areas allowed for sampling at 66% of sites located on private property. During 2007 and 2010, the Warner Lakes SMU was monitored intensively where surveys were completed at a total of 132 sites and 186 sites over the course of the entire study.

Warner Lakes redband trout abundance declined by 23% since last surveyed intensively in 2007. However, 2010 estimates show over a 50% decline from the previous two SMU level sampling years. Note that in population level sampling years 30 sites from each population are surveyed where in SMU level sampling years 30 sites total over the entire SMU are sampled.  Variability in the level of sampling may account for some of the difference in abundance which suggests that SMU level sampling over estimates abundance in this SMU.   

Redband Trout Stressors:

Factors, other than seasonal flow, that likely affect trout productivity are flow diversions, migration barriers, riparian habitat, competition with exotic salmonids, and climate regime.  Continued habitat fragmentation, degraded habitat quality and limited connectivity may hinder movement  and reduce abundance. Protection of current populations requires increasing the size and extent of populations, maintaining genetic and life history diversity, increasing connectivity, minimizing anthropogenetic stressors, and improving adaptive management. 

Project Overview (PowerPoint presentation)

Miller, S.A., S.E. Jacobs, S.L. Gunckel, and S. Richardson. 2010. Evaluation of a sampling approach to monitor the status of Great Basin redband trout in Southeastern Oregon. Oregon Department of Fish and Wildlife, Information Report 2010-02, Corvallis.