The Chargers signed Fisk from the practice squad to the active roster Saturday, Kris Rhim of ESPN.com reports.
Fisk was unable to make the Chargers' 53-man roster at the end of training camp, but he opted to stick around on the Bolts' practice squad. He hasn't been elevated this season, but he is now on the active roster and will serve as the Chargers' No. 4 tight end behind Will Dissly, Hayden Hurst and Stone Smartt (ankle).