UC Davis Research Project 1

Movement and survival of yearling steelhead through the Central Valley, CA

We will examine the survival and movement patterns of steelhead trout (O. mykiss) smolts migrating from the upper Sacramento River to the San Francisco Estuary through the use of ultrasonic telemetry. This study can be viewed as a classic mark-recapture experiment with multiple recapture locations and complete capture histories. From the data collected we will be able to reconstruct each fish’s migratory pathway, and examine how natural and anthropogenic covariates affect reach specific rates/residence time and survival.

A detailed lifecycle model for Central Valley salmonids is seriously lacking in the realms of smolt survival and spatio-temporal migratory patterns. The data gathered from this project will be used to:

  1. Describe reach-specific rates of survival and movement of juvenile steelhead from the upper Sacramento River to the coastal ocean.
  2. Explain the variation in reach-specific rates by examining natural and anthropogenic covariates, such as water velocity, water temperature, habitat structure, etc.

For three years we will surgically implant Vemco V9 tags into the peritoneal cavity of 200 steelhead smolts raised at the Coleman National Fish Hatchery (CNFH). These new ultrasonic tags are small enough (under 5% of fish body weight) that they do not affect swimming performance, predation rates, or growth rates of the juvenile salmonids.

Tags will be implanted into the peritoneal cavity of 13 steelhead smolts each day, five days a week, for four weeks in January. After the 13 fish have been held for a one week long post-implantation period they will be released. This procedure will be repeated until all 200 steelhead smolts are released. By spreading out when the smolts are released we can compare environmental variables affects on movements, and it will help to decrease the potential for “tag collisions” (fish not being detected because of multiple pinging at a monitor). We will be expanding the already existing array of 32 monitors in the Sacramento River used to record the movements of green sturgeon. The additional monitors will allow us to gain a better understanding of where juvenile salmonids may be diverted from their migratory routes, when they enter the Grizzly, Suisun, and San Pablo Bays, and when they finally depart from the San Francisco Estuary at the Golden Gate Bridge.

We have deployed all monitors from Redding to the Golden Gate Bridge and will be adding more units as they are purchased. Steelhead tagging has been completed for the 2007 season with the exception of steelhead to be tagged for manual tracking. We have released all of the fish and are interrogating the monitors in all five regions. We have had little trouble locating, retrieving and downloading monitors and should have all of the tag detection files in hand within the next few months. We will be adding tag detection files to the database and making them available on the web page as soon as possible.