UC Davis Research Project 2

Seasonal comparison of movement and depth distribution of steelhead in the Sacramento River and SF Bay

Very little is known about the movement patterns of juvenile steelhead trout. We have tracked three hatchery juvenile Steelhead trout tagged with Vemco V9 ultrasonic pressure sensing tags. Through the use of these tags it was possible to track fish position and depth for multiple days. In addition to collecting data on the fish’s position and depth, physical parameters such as temperature, salinity, dissolved oxygen and turbidity were recorded using a Hydrolab. Fish were tracked during the summer and winter to examine differences in seasonal movement patterns. Juvenile steelhead trout tracked during the summer moved during the daytime but held within approximately 0.5 km of where they stopped after dusk, and began to move shortly before sunrise. The tagged steelhead tended to spend the majority of their time in the upper two meters of the water column except when coming to areas of confluence or before holding or starting to move. By characterizing the movement patterns of these smolts we will be able to better understand what behaviors other juvenile tagged steelhead may be exhibiting between automated monitor sites along the Sacramento River at various times of the year.

While other projects are focusing on the migratory and larger scale movements of juvenile steelhead and Chinook this project aims to answer questions of habitat preferences and fine scale spatial movements while adding a depth component. We hope to characterize the behavior and movements of juvenile steelhead in relation to temperature, salinity, diel patterns and flows in order to better understand what might be going on between stations rather than only considering reach specific rates and needing to imply that habitat preference.

Juvenile steelhead smolts have been implanted with V9 continuous pingers with pressure sensors. This tag is less than 5% of the fish body weight, and thus will not affect the swimming or survival of the tagged fish. After the steelhead are implanted with the tag they will be held for a five day recovery period during which time their health will be closely monitored. Before the fish are released in the wild they are held in a net pen for 24 hours to allow each individual time to acclimate to the river without being vulnerable to predation. Once the holding period is complete the tagged fish will be released and tracked continuously for five days.

Two-hatchery steelhead have been tracked during the summer of 2006. The first fish was released on the Sacramento River at Ko-Ket Resort near Isleton, CA and tracked for more than 24 hours before the track was broken off. The second steelhead trout was released just outside of the Pittsburg Marina after being held in a net pen for 24 hours to allow the fish to acclimate to water conditions before being released and tracked. The second juvenile steelhead was tracked for over five consecutive days before the track was broken off. We currently preparing for winter/spring manual tracking.