Non-native salmonids are impacting native salmonid populations throughout the Pend Oreille Subbasin. Competition, hybridization, and predation by non-native fish have been identified as primary factors in the decline of some native bull trout and cutthroat trout populations. Therefore, the goal of this project is to implement actions to suppress or eradicate non-native fish in areas where native populations are declining or have been extirpated. These projects have been identified as critical to recovering native bull trout and westslope cutthroat trout (WCT).

Westslope cutthroat trout have recently been extirpated in upper Cee Cee Ah Creek due to displacement by brook trout. Prior to implementing non-native fish removal and WCT translocation in upper Cee Cee Ah Creek, an extensive public outreach program was initiated.  In 2007, much of the effort for this project was made towards public education and involvement in using piscicides for native fish recovery.  To date, public acceptance of using piscicides as a management tool has been accomplished.  In 2008 and 2009,  Cee Cee Ah Creek was treated with rotenone to eradicate brook trout. Re-invasion of the treatment area is impossible due to the Cee Cee Ah Falls.  Another rotenone treatment is planned for 2010 to ensure that eradication is successful.  Once eradication is complete, cutthroat trout will be translocated from nearby watersheds.    

Assessments completed through project 1995-001-00 have identified WCT and brook trout distribution throughout the Upper West Branch Priest River (UWB) watershed.  WCT are at relatively low densities and confined to headwater reaches.  Two tributary streams - Colza and Paqua creeks, were found to be void of fish.  If appropriate numbers of WCT are available in mainstem UWB, WCT will be translocated into the fishless streams to expand distribution of WCT in the watershed.  Genetic diversity of the mainstem WCT population is high enough to be an appropriate donor population.  However, population abundance relative to effective population size will need to be evaluated if the mainstem UWB WCT population is to used as a donor population.  Therefore, UWB will be intensively electrofished in 2010 to estimate WCT abundance in UWB.

The Tribe recently was awarded funding to conduct watershed assessments using NetMap (www.netmaptools.org), a coupled watershed database and analysis system to create spatially specific analyses of watershed processes and patterns pertinent to habitat restoration. NetMap is comprised of a community-based set of watershed databases and analysis tools designed to support diverse natural resource management including restoration, conservation, forestry, monitoring and wildfire planning.  The project manager and personell from Earth Systems Institute (ESI) wil develop a piscicide tool in NetMap to predict the best locations for reducing populations of non native trout species and for enhancing recovery of native fishes. ESI will develop a piscicide tool in NetMap to predict the channel reaches in the study area where piscicide treatments are appropriate for the recovery of native fish species. Parameters may include: i) natural and artificial barriers, ii) cutthroat habitat suitability (using HIP modeling, another task in the project); iii) present cutthroat trout presence or absence, iv) distance to appropriate donor population, v) live stock grazing, vi) vegetative condition of riparian zone (including present wood abundance), and vii) private ownership downstream (percent of area). Other potential parameters include domestic surface water rights and angler use.

The Tribe, through various funding sources, has completed a conceptual design for restoration of Goose Creek, a tributary to UWB (see project 1995-001-00 for details).  A fish passage barrier is included as part of the stream channel reconstruction design.  Except for 2 small (>0.5 mile in length) headwater stream segments, brook trout are the only salmonid present in Goose Creek.  The barrier will be constructed because future piscicide treatments are planned for Goose Creek and no natural barrier is present in the watershed to prevent re-invasion of non-native fish.  In 2010, the Tribe will have final design work for Phase 1 of the project, that includes the barrier.  The Non-native Suppression project will pay for the final barrier design.

The Idaho Department of Fish and Game has been working at suppressing lake trout in Upper Priest Lake through extensive gill netting.  Since 1997, over 10,000 lake trout have been removed from the lake (Figure 1); however, the population keeps rebounding, as fish appear to be immigrating from Priest Lake at an estimated rate of 2,000 per year (Liter et al. 2008 in press). Permanent suppression of lake trout in Upper Priest Lake would require techniques to block movement through the Thorofare, which connects Priest Lake to Upper Priest Lake.  Although complete control of immigration may not be achievable, a significant reduction in immigration could greatly augment the positive benefits of the lake trout removal from Upper Priest Lake.

In 2009, IDFG contracted Harbor Fisheries (with funding from USFWS) to install and operate trap nets and gillnets in the Thorofare in the fall on an experimental basis.  The intent of the project was to identify whether or not nets could be used to effectively curb immigration through the Thorofare in the fall.  Initially, the trap nets proved to be ineffective.  Lake trout were able to avoid the trap nets, despite using leads that completely spanned the Thorofare channel.  One challenge faced by any project aimed at controlling lake trout immigration is the need to maintain boat passage.  In 2009, the crew submerged a portion of the trap net leads and a portion of each gillnet and used markers to guide boats.  

Several modifications were made to the trap nets, and toward the end of the project, the nets were effective in capturing a portion of the upstream migrants.  The contractors were confident that additional modifications, including larger throats, heavier lead lines on the leads, and staggering leads to create a boat channel would further improve trap efficiency.  The progress and improvements made during the 2009 effort increase the likelihood of success with another year of effort.  

In 2010, this project will provide cost-share funding for the IDFG project and enable them to continue with lake trout removals in the Thorofare by installing and operating the modified trap nets and gillnets from early September through late October in an effort to refine the immigration control efforts.