BOSTON — Police Commissioner Ed Davis, a key figure in the investigation of the Boston Marathon bombing, spent his final day on the job Friday after seven years in the post.

Davis, 57, announced plans in September to step down as his boss, longtime Mayor Thomas Menino, was preparing to retire at the end of the year.

One of Davis’ final tasks was ensuring police kept fan celebrations under control after the Red Sox’s World Series victory this week at Fenway Park. About 10 people were arrested but few serious problems reported.

Superintendent-in-Chief Daniel Linskey will oversee security and crowd control during Saturday’s duck boat parade honoring the Red Sox. Davis said he was confident police would do a good job.

“I know there is a great team here and they’ll be just fine without me,” he told The Boston Globe in an interview Thursday.

Davis twice testified before congressional panels in the aftermath of the April 15 attack, which killed three people and wounded more than 260 at the marathon finish line. He called for better information-sharing between federal agencies and local departments about potential terrorist threats.

Davis said he had not ruled out leading another big-city department sometime in the future.

“I might have another police department in me at some point in time, but I’m really looking at the private sector right now for a couple of years,” he told the Boston Herald.

Davis has accepted a fellowship at the John F. Kennedy School of Government at Harvard University.

Davis’ permanent replacement will be chosen by the city’s next mayor. City Councilor John Connolly and state Rep. Martin Walsh square off Tuesday in the mayoral election, with the winner taking office in January.