After having introduced the 4,500 Fall run (all PIT tagged) and 100 Late-Fall yearlings (all PIT and JSATS tagged) into the fields the previous week, emphasis has turned to utilizing the network of seven PIT readers at the rice boxes to collect data on fish movements within the field and out the field drain. All 4,500 Fall run were released into the 2nd to highest check in the field. Therefore, to exit the field these fish had to swim through at least three sets of modified rice boxes. The day after introduction about 125 of the 4,500 salmon had exited. This initial exodus of a small but notable percentage of fish in the first 24–48 hours is a known phenomenon. By Day #2, however, the number exiting dropped sharply to about 32 demonstrating that over 4,300 of the 4,500 fish were settling into the field to enjoy the populations of floating bugs for them to eat. Included in the visuals for this week is a picture and a short video of this nutritious floating smorgasbord of delicious zooplankton for the salmon to dine on while in the field. Like the previous year’s field season, we quickly demonstrated the ability of these fish to effectively move through the modified rice boxes with the holes and notches within just one day.
The UC Davis science team continued counting and releasing fish daily from the fyke and conducting seining operations. We had counted about 90 natural-origin salmon by this time. Based on salmon size-class assessment, we suspected we had counted mostly Fall run (about 75), 1 late-Fall run, 8 Winter run and 3 Spring run during seining and fyke net trap operations. We have added three more fish (underlined in this week’s update) to the list of other fishes observed including splittail, shad, golden shiner, Sacramento sucker and hatchery steelhead within the study fields. Occasional predators include bass, sunfish, pike minnow. As mentioned previously, the larger predators were sampled for diet contents via gastric lavage, some PIT tagged and released.
The UC Davis Team had also successfully deployed all the JSATS receivers in the bypass canal, both upstream and downstream, so were fully prepared to monitor JSATS-tagged fish movement within the bypass.
Temperature and DO monitored continued, in real-time, with autonomous HOBO data loggers and there were no measurements of concern by that time even though a couple of daily temperature readings were in the high 60’s.
The grower continued to be able to reliably maintain the desired flood depths of 10–12 inches in each check.