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 is a collaborative project conducted by staff of the U.S. Fish and Wildlife Service (USFWS) and the U.S. Geological Survey (USGS).  Each of these two agencies brings expertise in fish tagging and data analyses specific and complimentary to the project's two objectives.  Staff of the USFWS is primarily responsible for accomplishing objective 1 activities that focus on tagging fish with passive integrated transponders (PIT tags), uploading the tagging data to a central database, and providing managers with in-season and post-season analyses.  Staff of the USGS is primarily responsible for accomplishing objective 2 activities that focus on tagging fish with radio transmitters, downloading detection data from telemetry stations, and providing managers with in-season and post-season analyses.  Staff of both agencies coauthor refereed articles in international journals.  Radio tags are purchased by BPA through a contract with Lotek.  

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.

Staff of the USFWS accomplish this objective as follows.  Wild fall Chinook salmon subyearlings are implanted with PIT tags while rearing along the free-flowing Snake River upstream of Lower Granite Reservoir.  The PIT-tag data are uploaded weekly to the PIT-tag Information System, where in turn, it is downloaded, analyzed, and posted in real time on Internet services.  The downloaded data are used to determine when wild fall Chinook salmon are in Lower Granite Reservoir or passing Lower Granite Dam.  The Fish Passage Advisory Committee and the Technical Management Team use this timing information to plan and implement summer flow augmentation.  Staff of the USFWS also analyze these data to determine if summer flow augmentation increased survival of wild fall Chinook salmon subyearlings.


Objective 2: Understand how summer flow augmentation affects water temperature, water velocity, juvenile fall Chinook salmon migratory behavior, and juvenile fall Chinook survival salmon in Lower Granite Reservoir.

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.