BPA Project Number:  2002-002-00
Contract Number:  00019398
Contract Title:  Feasibility of Enhancing White Sturgeon Spawning
FY2006

Project Description:
Kootenai sturgeon recruitment has failed, apparently because fish are spawning at sites where conditions are not suitable for incubation and early rearing.  Sturgeon are broadcasting eggs over an unstable sand bottom in the gradient transition zone downstream from Bonners Ferry.  Shifting sand rapidly covers and suffocates embryos and/or traps larvae.  Eggs deposited over open substrates are also exposed to predation by other fishes.  Sturgeon more typically spawn over clean gravel and cobble substrates where the eggs may settle or are washed into rock interstices.  High velocities, turbulence, and nearby eddy or pool areas for staging are also common denominators of spawning sites used successfully by other white sturgeon populations.

Rock substrates that appear to be suitable for spawning and incubation are available upstream from current spawning areas but fish continue to spawn in unsuitable conditions downstream.  Rock substrates are also available in the spawning reach but along the levees rather than in the river channel where spawning occurs.  Levee toes were armored with alluvial rock hauled in from terrestrial sources.  Core samples indicate that little rock exists in the river channel where sturgeon are currently spawning so it does not appear that fish are spawning in historically-suitable areas which have been degraded by habitat changes.  Velocities in the current spawning reach are near the low end of those favored by other sturgeon populations.  Peak velocities are around 1.2 meters per second (mps) and more typically less than 1 mps.  Preferred mean water column velocities for spawning by sturgeon in other areas are typically between 1 and 3 mps.  The mechanism of the velocity effect might include egg dispersal, egg aeration, predator exclusion, or association with clean rock substrates that provide suitable egg incubation and larval hiding sites.  

It is unclear why Kootenai River fish do not seek more suitable substrates.  One hypothesis is that a downstream shift in the velocity transition zone has resulted in fish spawning over unsuitable substrates. A combination of Kootenay Lake regulation, levee construction in the Kootenai Valley, and flow regulation from Libby Dam has altered hydrodynamics in the gradient transition zone and may account for the shift in velocity cues.  In the altered system, velocity and turbulence cues that previously coincided with rocky substrate now occur over sand.  Changes in hydrodynamics have also increased deposition of fine material in areas immediately upstream of Bonners Ferry which might previously have provided suitable combinations of substrate and velocity for sturgeon spawning. In addition to substrate and velocity conditions, recent research and observations involving various sturgeon species suggests that turbulence associated with complex, higher energy flow fields, and inter-gravel or interstitial flows may be associated with or required for successful recruitment.

Since 1994, Libby Dam discharges during spring have been augmented and shaped in an attempt to stimulate natural recruitment of Kootenai sturgeon.  Recruitment has been positively correlated with flow in other white sturgeon populations.  Monitoring of sturgeon movements in the Kootenai suggest that augmented spring flows may have cued pre-spawning migrations and affected spawning location. However, they have not been sufficient to move fish upstream into better spawning habitat in the braided or canyon reaches, or to create the appropriate conditions in the current spawning habitat if that is required to reestablish natural recruitment..
Without immediate implementation of substantive habitat restoration measures, there will soon be too few adults to take advantage of improvements.  However, significant habitat improvements in a river the size of the Kootenai will be costly and benefits of any specific action remain uncertain.  Declining sturgeon numbers and limited resources for large-scale habitat restoration programs do not afford the luxury of implementing large-scale experiments without better information to guide design.  We are likely to get only one good chance at physical habitat restoration and it is imperative that alternatives are selected that provide the best chance for success.  However, this imperative will also require that something substantive is attempted before time runs out.  Extensive studies have been completed of sturgeon behavior and potential limiting factors in attempt to reduce the uncertainty in identifying effective remedies.  These studies have brought us now to the point where it is time to experimentally evaluate promising alternatives.

Two distinct strategies have been identified for physical restoration of suitable spawning habitat conditions for Kootenai white sturgeon.  One strategy is to bring suitable habitat to the fish.  The second strategy is to transport or attract the fish to suitable habitat.  
Alternatives for bringing the habitat to the fish include:
a. artificially introducing rock substrate into current spawning areas,
b. using mechanical devices to increase velocities at or upstream from existing spawning sites.
Alternatives for bringing fish to the habitat include:
c. using a combination of lake level regulation and Libby Dam discharge to shift the velocity transition zone upstream,
d. altering conditions in the braided reach upstream from Bonners Ferry to restore suitable migration, spawning, and incubation conditions, or
e. physically transplanting spawners or eggs into upstream areas where suitable incubation and early rearing habitat is available.(Further detail for alternative e found in 5-year Plan)

This study evaluates the feasibility of alternatives for physical restoration of suitable spawning habitat conditions in the Kootenai River.  The intent is to use a combination of computer modeling, physical modeling, and small scale field experiments to guide development of a larger scale habitat enhancement project.  Feasibility evaluations will be based on whether small-scale treatments produce desired physical and hydraulic conditions. The biological response to physical habitat improvements is the subject of subsequent components of a comprehensive sturgeon conservation and recovery plan.  The relationship of the habitat improvement feasibility study to other elements of the comprehensive program is described in more detail the 5-year implementation plan.  

This pilot study is Phase II of the project for evaluating physical and hydraulic characteristics of the Kootenai River that was funded by the Bonneville Power Administration (Project No. 200200200) and implemented by the KTOI and the USGS.  Phase I involved measurement of physical habitat conditions and development of a simulation model of Kootenai River spawning and potential spawning areas.  Phase II involves the evaluation of alternatives for physical restoration of suitable spawning habitat conditions.  Contracting for the implementation of one part of this project (Shorty's Island Pilot Project) will be directly between BPA and the ACOE for $250,000.  The land lease and other monitoring elements for the Shorty's Island Project implemented by the ACOE are identified in this SOW.  Effective habitat restoration alternatives identified by this project will be proposed for additional funding (Phase III), and may include cost share with USACE 1135 grants for habitat improvement projects.

This project is coordinated through the USFWS White Sturgeon Recovery Team. The project is reflective of and integrated with ESA recovery goals for the white sturgeon outlined in the 1999 USFWS Recovery Plan and the 2000 Biological Opinion for White Sturgeon (RPAs 3i and 3j).  Phase II of the project is outlined in the 2005 USFWS White Sturgeon Recovery Team document entitled "FEASIBILITY STUDY FOR THE RESTORATION OF SUITABLE SPAWNING HABITAT CONDITIONS FOR KOOTENAI RIVER STURGEON".  This project is also consistent with and complements the ACOE Habitat Evaluation and Recovery Strategy for White Sturgeon. Additionally, this project is implemented as part of the Adaptive Management Framework outlined on page 94 of the Kootenai Subbasin Management Plan.