Jose Ernesto Magana plunged off the Brazos Bridge around 2:45 a.m. The railroad trestle is near the Napa County Airport.
Magana's fishing companion called 911 minutes after he went into the water.
Firefighters walked the river banks and searched the water using boats. A Coast Guard helicopter looked for Magana and a Highway Patrol helicopter also flew over the river late this afternoon -- looking for any signs of the victim.