There are two common strategies for releasing juvenile salmon from state and federal salmon hatcheries in the Central Valley. One strategy is the release of hatchery salmon smolts at or near the hatchery where they are produced. The other strategy is trucking the smolts from the hatchery and releasing them into the Bay. There is much controversy and argument over the relative merits of the strategies. There can be little argument that release into the Bay generates far more adult salmon than release near the hatcheries.
Consider what occurred with two American River release groups after their release in May 2018 and return as adults in 2020. Release group #061465 was 669,000 fall-run smolts (3-4 inches long) that were transported 20 miles downstream from the American River (Nimbus) Hatchery and released into the mouth of the American River under the Jibboom Street Bridge. Release group #061467 was 650,000 fall-run smolts transported approximately 100 miles downstream to net pens at the Wickland Oil Terminal for release into eastern San Pablo Bay, about 20 miles from the Golden Gate Bridge and the Pacific Ocean.
The estimated percent survival based on tag recoveries was 0.04% for group #061465 (released near the hatchery). The estimated percent survival was 2.20% for group #061467 (released in San Pablo Bay). The returns by locations are shown in Figures 1 and 2. These relative results are common.