It’s a lovely December morning in Rio Vista, a town of 10,000 in the Sacramento-San Joaquin Delta. The sky is a soft blue, the sun brings welcome warmth against the chill, and the water is calm with just a hint of ripples―ideal conditions for the team of state and federal biologists standing on a boat launch on the Sacramento River at 8:30 am. They’re here to release captive-raised Delta smelt, a small endangered fish unique to the region, into the wild.