The effects of summer flow augmentation on the migratory behavior and survival of juvenile Snake River fall Chinook salmon

BACKGROUND
Dams reduce the survival of Chinook salmon smolts during early seaward migration.  Summer flow augmentation is implemented annually to mitigate for Snake River fall Chinook smolt mortality caused by the four dams in the lower Snake River by increasing downstream migration rate and survival.  There are two philosophies regarding summer flow augmentation within the resource management community of the Columbia River basin.  One philosophy embraces summer flow augmentation based on studies that show flow augmentation increases the migration rate and survival of fall Chinook salmon smolts.  The other questions the existing migration rate and survival studies, and advocates the use of limited reservoir water for other fishery and economic purposes.  For the present and near future, summer flow augmentation will be implemented annually as one measure to recover Snake River fall Chinook salmon listed for protection under the Endangered Species Act.  Fishery managers will require pre-augmentation data to develop annual water management plans, and post-augmentation data for evaluation.  Fishery managers also need new and more detailed information on how summer flow augmentation affects water temperature, water velocity, juvenile fall Chinook salmon migratory behavior, and survival in Lower Granite Reservoir.

COORDINATION
This project is comprised of three contracts.  The first is with the U.S. Fish and Wildlife Sevice to complete work described under Objective 1.  The second is with the U.S. Geological Survey (this contract) to complete work described under Objective 2.  The last contract is with Lotek Wireless, Inc. which will provide radio tags for the work described in Objective 2.  The three different contracts are the most cost-effective way of conducting this project because the greatest savings in reduced overhead rates are realized.

GOAL
Our research goal is to provide fishery managers with an understanding of the migratory behavior and survival of juvenile fall Chinook salmon in the Snake River, so that maximum recovery benefits of summer flow augmentation can be realized.

OBJECTIVES AND RATIONALE
Objective 1: Provide information to fishery managers to maximize the effectiveness of summer flow augmentation. (To be completed by USFWS)

Rationale: To be effective, summer flow augmentation must be implemented when juvenile fall Chinook salmon are rearing or migrating downstream in Lower Granite Reservoir. The Fish Passage Advisory Committee and the Technical Management Team provide forums for planning and implementing summer flow augmentation.  Much of the data used by fishery managers in these forums are supplied by our project in the form of records compiled on wild fall Chinook salmon juveniles we tag with Passive Integrated Transponder (PIT) tags (Prentice et al. 1990).  The PIT-tag data are provided weekly each year via the PIT-tag Information System, where in turn, it is downloaded, analyzed, and posted in real time on Internet services (e.g., DART; Program RealTime, Burgess and Skalski 2001).  We analyze the PIT-tag data to evaluate the effectiveness of summer flow augmentation after it is implemented.  Objective 1 of our research will help to maximize the effectiveness of summer flow augmentation by providing real-time data for planning, and post-season analyses for evaluation.  The U.S. Fish and Wildlife Service is responsible for conducting this work and completing this objective for the overall project.

Objective 2: Understand how summer flow augmentation affects juvenile fall Chinook salmon migratory behavior in Lower Granite Reservoir. (To be completed by USGS)

Rationale:  Summer flow augmentation is intended in part to ameliorate the negative effects of high summer temperatures on migrating subyearling fall Chinook salmon.  This is accomplished by releasing cool water from Dworshak Reservoir, which flows down the Clearwater River and into Lower Granite Reservoir.  Although summer flow augmentation may benefit fish in Lower Granite Reservoir, it may be a factor in some Clearwater River fall Chinook salmon adopting a reservoir-type life history (Connor et al. 2005).  Migration rate and survival information on fish originating from the Clearwater River has been sparse because of low sample sizes and the fact that many fish are not detected at Lower Granite Dam.  Recent advances in radio telemetry will allow us to tag fish as small as 85 mm.  This approach will be used to monitor fish migration rates in the Clearwater River and Lower Granite Reservoir and determine when and where fish are apt to delay their seaward migration during summer flow augmentation.  This will allow us to better determine the effects of summer flow augmentation on Clearwater River fall Chinook salmon.  Staff of the USGS will accomplish this objective as follows.  Hatchery subyearling fall Chinook salmon will be implanted with radio tags and released in the Snake and Clearwater rivers.  Radio telemetry receivers will record the time and date of each fish detected at various sites in the Snake and Clearwater rivers.  This data will be analyzed for differences in migration rates and behavior of fish released in the two rivers.  This will provide information on migrational delay and the degree to which fish respond to summer flow augmentation.