Great Basin Redband Trout Overview
Malheur Lakes SMU
Great Basin Overview:
The summer 2011 field season marked the completion of the fifth 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 2008 and
2011 sampling years complete the population level sampling for the
Malheur Lake SMU. A total of 1261 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. The 2011 represents the
first increase of landscape-wide abundance since 2007. Estimates of
landscape-wide abundance across all five years of the study averaged
816,000 + 16%.
The Malheur Lakes SMU is comprised of 9 populations that were grouped
into 6 areas (Silver, Silvies, East-Burns, Blitzen, Riddle, and McCoy).
Landowner participation in these areas allowed for sampling at 73% of
sites located on private property. Continued landowner participation is
key to furthering our understanding and conservation of redband trout.
During 2008 and 2011, the Malheur Lake SMU was monitored intensively
where surveys were completed at a total of 158 sites and 402 sites over
the entire study.
Abundance of Malheur Lake age-1+ redband trout were highest in 2007. Abundance declined by 27% since 2007 but has also increased since sampled last year. 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. Likely the high water year this year contributed to higher abundance of fish in 2011. Patchy distribution and low fish densities may be due to habitat quality or a less accurate sample frame.
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
Miller, S.A., S.E. Jacobs, S.L. Gunckel, and S. Richardson.
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.
ODFW Oregon Native Fish Status Report (2005)
Dambacher, J.M., K.K. Jones and H.W. Li. 2001.
The distribution and abundance of Great Basin redband trout:
an application of variable probability sampling in a 1999 status review. Oregon Department of Fish and Wildlife,
Information Reports 2001-08, Portland.