Introduction/Location.  Bull trout were listed as threatened under the ESA in 1998 due to declining populations.  The USFWS recommends monitoring populations in subbasins where little is known including the Grande Ronde and Imnaha Subbasins.  Redd counts have been conducted for eight to nine years in the project area; however, a minimum of 15 years is needed to determine population trends.  Surveys are conducted in selected streams within Lostine, Bear, and Big Sheep Creeks and the Imnaha River in the Grande Ronde and Imnaha Subbasins.

Objectives of the bull trout surveys include:

• Locate bull trout spawning areas
• Determine redd characteristics
• Determine bull trout timing of spawning
• Collect spawning density data
• Map location of bull trout spawning reaches
• Determine and compare the spatial distribution of redds along the Lostine River in 2005, 2006, and 2007
• Assess population trends for the local bull trout populations
• Use this information for the long-term recovery of bull trout

Methods.  This project is part of a larger effort in NE Oregon and SE Washington that is occurring at the same time (September - October).  Bull trout spawning surveys have been conducted on similar index areas for selected Grande Ronde and Imnaha River streams from 1999 to 2007.  Surveyors walk the rivers through the selected “index areas” to locate, measure and record the number of bull trout redds.

Survey Frequency
Surveys are typically conducted twice (mid and late bull trout spawning season).  One-time surveys are conducted late in the spawning season on the upper Imnaha River and tributaries, and Bear and Goat Creeks due to access and funding limitations (in 2007, surveys were conducted twice on Bear and Goat Creeks).

Results and Discussion.  Bull trout spawning areas were documented for the surveyed streams from 1999 to 2007.  In 2006 and 2007, the Imnaha had a large distribution of bull trout redds that extended further downstream than in past years; which Is likely due to limited passage of bull trout at the upstream falls (attributable to low flow conditions).  Redd size is related to fish size, smaller redds such as in Cliff Creek are made by smaller (resident) fish and larger redds such as in S.F. Imnaha are made by larger (fluvial) fish.  Brook trout have been observed on the spawning areas of the Lostine and are known to inhabit Bear Creek.

Timing of Spawning
Generally, bull trout spawn during September 1 – October 15 in the surveyed streams, and as early as August 15 in the Imnaha River.

Spatial Distribution of Redds along the Lostine River 2005-2007
Bull trout redds on the Lostine River were often arranged in complexes.  Redds were primarily located in the French Camp to Shady Falls and Bowman to French Camp reaches along the Lostine River in 2005, 2006 and 2007.  High site fidelity is noted by the overlap in 2005-2007 redds, especially in the upper reaches.

Conclusion.  The local bull trout populations are relatively stable within the survey period.  The Imnaha population is one of the strongholds within the Imnaha Subbasin and within the Wallowa Mountains.  Primary spawning activity on the Imnaha River occurs in the headwaters which lie within the wilderness.  Both fluvial and resident life history forms are present.  The Imnaha River bull trout are documented to be at low risk of extinction and the Big Sheep bull trout are “of special concern.”  The results of this study are consistent with this past assessment.  The Lostine River is considered a moderately-strong population within the Grande Ronde Subbasin.  The Lostine River and Bear Creeks contain brook trout and hybridization may be occurring.  Future genetic analysis of bull trout and brook trout is recommended to help determine the significance of this threat.

Reports

2007 Wallowa Mountains Bull Trout Spawning Report

2006 Wallowa Mountains Bull Trout Spawning Report

Acknowledgements.  Oregon Department of Fish and Wildlife, Wallowa-Whitman National Forest, U.S. Fish and Wildlife Service, Nez Perce Tribe, National Marine Fisheries Service, Anderson-Perry, and we especially thank these individuals : Brad Smith, Ken Bronec, Mac Huff, and Peter Cleary.  There are many others too numerous to thank.