Relationship to Columbia River Fish and Wildlife Program

The Columbia River Basin Fish and Wildlife Program (FWP); (Northwest Power Planning Council, September 13, 1995), section 10.3C.1, states that Idaho Fish and Game shall "Analyze methods to avoid or minimize entrainment of kokanee at Dworshak Dam including behavioral avoidance devices such as strobe lights, pneumatic hammers, bubble screens and sound generators, as part of development of integrated rule curves for Dworshak Reservoir".  Also, that we shall "implement annual mid-water trawling to further define the relationship between the fishery, kokanee densities and the water year" (Section 10.3C.2).  And lastly, that we shall "implement annual kokanee spawner counts in appropriate creeks" (Section 10.3C.3).  Section 10.3C.5 and 10.3C.6 directs the Bonneville Power Administration to implement and fund these research activities.  This proposal addresses all three of these activities.
This project is also consistent with management objectives of the State of Idaho.  These objectives are spelled out in Idaho Fish and Game's 5-year management plan for Idaho.  It also conforms to Council prioritization process according to program measure 10.1B.  This measure gives a high priority to "resident fish substitution measures in areas that previously had salmon and steelhead, but where anadromous fish are now irrevocably blocked by federally operated hydropower development"; this is the case with Dworshak Reservoir.  The natural river habitat has changed into a fluctuating reservoir.  This project attempts to improve sport fisheries on the native and introduced fish within this new habitat.  It is also a principle of the FWP to "Protect, mitigate and enhance resident fish in hydropower system storage projects to the fullest extent practical from negative impacts associated with water releases".  Our work on avoiding entrainment losses attempts to do this.

Entrainment losses of resident fish are a major concern in the Columbia Drainage.  Entrainment losses of kokanee have been shown to be the main factor causing wide fluctuations in the abundance of kokanee in Dworshak Reservoir.  Strobe lights have shown positive benefits for other species such as Atlantic salmon, coho, chinook, and American eels (Patrick 1982, Nemeth and Anderson 1992, Winchell et al. 1994, Ploskey and Johnson 1997).  Strobe lights were found to repel kokanee to a distance of 30 m or more, with no habituation in our own studies.  On site testing of strobe lights on Dworshak Dam is the next logical step in solving the problem of entrainment losses.

Our findings will hopefully benefit several species of fish within the reservoir.  Kokanee are the primary species that will be benefited.  They are the largest resident fishery in the Clearwater drainage with up to 140,000 hours of fishing effort.  But the project also provides direct benefit to non-target species.  Avoiding entrainment losses of kokanee could also minimize the losses of cutthroat, rainbow trout, and/or bull trout (the effect of strobe lights on these species has not yet been tested).  An improved kokanee population provides forage for the reservoir's bull trout and smallmouth bass.  Also, having 300,000+ kokanee migrate up tributary streams and die each fall could add significant nutrients to these stream systems, thereby potentially enhancing the reservoir productivity as well.

Coordination

The project leader will keep the Resource Management Office of the U.S. Army Corps of Engineers apprised of progress and findings of the project.  Project information will be available to the Nez Perce Tribe since Dworshak Dam and part of Dworshak Reservoir is located on tribal land.  Project findings will be shared with other kokanee researchers at the International Kokanee Workshop, or other professional society meetings, as a form of scientific project review.  Quarterly reports and annual reports will be submitted to the Bonneville Power Administration to keep them apprised of project activities.  As new tests are conducted, data analyzed, and findings become available; the results will be presented at an American Fishery Society Conference and submitted for publication.

Summary of the Project

Previous work on Dworshak Reservoir has documented that kokanee populations are extremely variable (Maiolie and Elam 1992, Mauser et al. 1989).  Density of kokanee recruited to the fishery has ranged from 5 to 110 kokanee/hectare.  When densities are high, Dworshak Reservoir becomes one of the best kokanee fisheries in the State, accounting for a harvest of over 200,000 fish annually.  When densities are low, catch rates, harvest, and fishing effort are sharply reduced.  These studies also indicated that entrainment loss of kokanee is the single most important factor causing variability in the population (Maiolie and Elam 1992).

Hydroacoustic studies in 1994 and 1995 tracked the movements of kokanee up and down the reservoir.  They showed that kokanee congregated near the dam during winter and were much more vulnerable to entrainment in late winter and early spring.  They also showed that kokanee were least susceptible to entrainment during early fall.  Research work in 1994-96 utilized the selector gates on the dam to try to avoid fish losses.  Three record year classes were achieved.  However, studies in 1996 documented the loss of 1.3 million kokanee from the reservoir during a period of high water releases (Maiolie and Elam 1998).  This single event affected four year-classes of fish in the reservoir.  Selective water withdrawal was impossible because the selector gates need to be raised when the reservoir elevation is low.  Dworshak Reservoir has also become increasingly important for providing increased river flows to benefit salmon and steelhead.  During May, July and August, large amounts of water are typically released to aid smolt migration and cool river temperatures in the lower Snake River.  This changed operation, however, has the potential to entrain additional fish.  Studies by the Electric Power Research Institute (Lawler et al. 1989), indicated that sound, light, and bubble curtains may be effective at inducing an avoidance response thus keeping fish away from turbine intakes without changing power plant operation.

Off-site studies in 1997 showed that kokanee are strongly repelled by underwater strobe lights at a flash rate of 300 to 450 flashes per minute and that no habituation to the lights occurred after an entire night of operation.  Our testing in 1998 indicated that strobe lights worked well at repelling kokanee in off-site lakes.  During 2000, a floating research platform was built upstream from the dam, which housed the strobe light gear and propane generator
On-site strobe light effectiveness studies in 2001 were shown to reduce fish densities by 88% (p = 0.009) when the lights were turned on.  Kokanee were also moved to depths of over 200 ft (well below the depth of the turbine intakes) when strobe lights were turned on.  There also appeared to be no tendency for fish to habituate to the lights during nights with the strobe lights flashing.  Continued effectiveness testing in 2002 progressed to preliminary testing in front of operating reservoir outlets.  Fish densities in front of the reservoir outlets averaged 253 fish/ha when no lights were present.  Mean densities dropped to 87 fish/ha when the strobe lights were turned on during three other nights of sampling.  This decline (66%) is a very promising reduction in fish density, especially in front of the discharging reservoir outlets (ROs), which have faster water velocities.  Test results indicated that a single set of nine lights may be sufficient to repel kokanee from a single reservoir outlet during the night.

In 2004, the Council provided the following direction to the project: "Close out project in 2005, funding report for evaluation.  No implementation. Sponsor should provide 2005 spending cap to complete report".  Total budget for the project was listed as $160,000; a cut of 50% from the previous year.  This current statement of work was designed to meet this budget.  Additional funding requests will be submitted in the future to continue activities on the project and we anticipate an increased range of activities once the Council approves the Subbasin Plans.   Three activities will be conducted: 1. an implementation plan will be developed with the U.S. Army Corps of Engineers that will show how strobe lights could be placed on the dam for long-term operation; 2. final testing of strobe lights will be conducted with fixed-location transducers monitoring the actual fish entrainment during the strobe light testing; and 3. an annual progress report will be written summarizing the previous year's effort to maintain optimum kokanee densities.

The Work Elements for this project fall under the following goal, objective, and sub-objective.

Goal:  The goal of this project is to improve the sport fishery in Dworshak Reservoir.

Objective:  Maintain an annual kokanee population of 30 to 50 adult kokanee/ha by reducing entrainment losses of fish.

Sub-Objective 1  Test strobe lights as a methods to minimize entrainment of kokanee at Dworshak Dam.