Fisher, 29, signed last spring as an unrestricted free agent, after spending the first six seasons of his NFL career with the St. Louis Rams. Fisher became an unrestricted free agent for the second time in two years and is free to sign with any other team.
The Lions have also released quarterback Drew Henson and signed wide receiver Demir Boldin.
Terms of the deals were not disclosed.
The 22-year-old Demir Boldin played at Wake Forest.
In 2008, Fisher had 37 tackles, no interceptions and five deflected passes in 14 games with eight starts for the Lions.
Detroit has added three veteran cornerbacks this spring -- Anthony Henry (Dallas), Phillip Buchanon (Tampa Bay), and Eric King (Tennessee) -- as unrestricted free agents, and Schwartz plans to dramatically revamp the position around the three.
A seven-year veteran, Fisher entered the league as a 2002 second-round draft choice by the Rams. The former Central Florida star was a starter in St. Louis, then signed a three-year, $9-million contract with the Lions last spring.
For his career, Fisher has appeared in 86 games with 74 starts. He has 336 tackles, nine interceptions, and 32 deflected passes. Fisher's best season was in 2003, when he intercepted four passes.
In his rookie season as coach, Schwartz has made rebuilding the Detroit secondary a priority for the club. The Lions ranked 27th in the league in pass defense in 2008. Their four interceptions was the NFL's lowest total. The Lions surrendered 25 touchdown passes, the third most in the NFL. They also allowed opponents a quarterback rating of 110.0, the worst in the league.
Len Pasquarelli is a senior writer with ESPN.com. Information from The Associated Press was used in this report.