Post-release Behavior and Survival of Hatchery and Natural Juvenile Fall Chinook Salmon

The Problem

Fall chinook salmon (Oncorhynchus tshawytscha) in the Snake River are currently listed as threatened under the Endangered Species Act (ESA). Because fall chinook salmon migrate seaward during the summer when flows are low and water temperatures are high, one management action being used to recover this stock is to provide summer flow augmentation to speed the travel time of seaward migrants and thereby increase their survival. There is much controversy surrounding the effectiveness of flow augmentation and unraveling the specific mechanisms of flow, temperature, and turbidity-all of which are highly correlated with each other.

Objectives

The goal of this study is to more clearly identify the relationships between water velocity and fish travel rates to determine if flow augmentation can increase velocities appreciably. In addition, because water released from Dworshak Reservoir on the North Fork Clearwater River is much colder that ambient river temperatures, it is hypothesized that juvenile fish from the Snake River may delay their migration when they encounter cooler water from the Clearwater River in the confluence area. A second objective is to determine the influence that cooler water from the Clearwater River has on the migratory behavior of juvenile migrants.

Methodology

Surgically implanting a radio tag.

This project uses radio telemetry to determine the relationship between fish migration behavior and environmental variables such as water velocity and water temperature both before and after summer flow augmentation. Fish will be collected at the Lower Granite Dam juvenile fish collection facility, surgically implanted with radio transmitters and released in both the Snake and Clearwater rivers. Fish will be monitored as they pass fixed-site radio receivers located throughout Lower Granite Reservoir and at Lower Granite Dam. Detection data will be analyzed to determine migration rates past detection sites and how those rates relate to water velocity and water temperature. Water velocity information will be collected along regularly-spaced transects throughout Lower Granite Reservoir. Mean cross-sectional velocities will be used to calculate a velocity exposure index for fish passing between detection sites with will be related to migration rates using regression analysis. Water temperature information will be collected in the Snake River from its confluence with the Clearwater River to Lower Granite Dam to describe the thermal environment of Lower Granite Reservoir. Fish selection of different water temperatures will be evaluated using temperature-sensing radio telemetry.

Highlights and Key Findings

2002 was the first year of this phase of the study and data is currently being analyzed and results will be available in a technical report later in 2003. However, this project collected similar information from fall chinook salmon tagged with temperature-sensing radio tags in 1998 and 1999 has been summarized and is the subject of a peer-review publication. In this work conducted in Little Goose Reservoir, we found no areas of thermal refugia and fish thermal exposure was a function of ambient water temperature and migration rate through the reservoir.

Where Are We Headed In 2003

This study will continue its second year in the summer of 2003. A technical report summarizing our results will be published in the spring of 2004.

Project Contact

Kenneth Tiffan
U.S. Geological Survey
Western Fisheries Research Center
Columbia River Research Laboratory
5501-A Cook-Underwood Rd.
Cook, WA 98605-9717

Email: ken_tiffan@usgs.gov
Phone: 509-538-2299
Fax: 509-538-2843

Publications