Each year Nimbus Hatchery releases approximately 4.0 million Chinook salmon smolts and approximately yearling 430,000 steelhead trout. The Chinook salmon releases are currently broken into thirds with 1.33 million released in the Lower American River at the Sunrise Avenue river access, 1.33 million released in the Lower American River under the Jibboom Street Bridge, and 1.33 million released to the San Pablo Bay via acclimation net pens. The two in-river releases are direct plants to the water from planting trucks using a long tube. The net pens are loaded from the planting trucks at Mare Island near the mouth of the Napa River, or on the south side of the Alfred Zampa Memorial Bridge in Selby using a Conoco Phillips dock. The fish are loaded into the net pens on a slack tide then, as the ebb tide starts, the net pens are guided off the dock by a pair of boats out into the Carquinez Strait. The fish acclimate for approximately two hours while the net pens drift with the ebb tide to the mouth of the San Pablo Bay where the fish are released. No more than two days in a row of Chinook salmon releases are conducted from the same location to reduce impacts of avian, fish, and pinniped predation. Sodium chloride salt is added to all hauling trucks as an osmoregulatory enhancer and antistressor, at 0.5 to 1.0 mg/L, and a commercial anti-foam food grade emulsion is added.

Yearling steelhead trout are released in the Lower American River at either the Howe Avenue or Sunrise Blvd. river access. Typically, steelhead releases are performed in the late afternoon and into the evening when possible to reduce avian predation.