NEW YORK, United States — Gap Inc. fell the most in more than three years after saying it will replace Chief Executive Officer Glenn Murphy, who was credited with reviving the apparel maker during his seven-year tenure, and posting disappointing September sales.

The shares slid 12 percent to $36.67 in New York, the biggest one-day decline since May 2011. They have now slid 6.2 percent this year.

Art Peck, who serves as president of Gap’s growth, innovation and digital unit, will take the CEO job on Feb. 1, the San Francisco-based company said yesterday in a statement. Gap said separately that September’s sales at stores open at least a year and online were little changed from a year earlier. Analysts had predicted a 1.2 percent gain.

Murphy, 52, joined the company in 2007 and helped it recover from a years-long sales slump that was exacerbated by the financial crisis and recession. The shares have more than doubled during his tenure, which also included the acquisitions of athletic-apparel brand Athleta in 2008 and luxury brand Intermix in 2012.

“Investors really like Glenn and don’t what to see him go,” Dorothy Lakner, a New York-based analyst at Topeka Capital Markets, said in an interview. “While people know Art Peck, maybe they feel they don’t know him quite as well as Glenn.”

As part of the succession plan announced yesterday, Bob Fisher, the son of Gap’s founders, will become non-executive chairman. Murphy had been chairman throughout his time as CEO.

Among the priorities for Peck, 59, will be working to increase the company’s digital sales at a time when mall traffic is dwindling and shoppers are increasingly going online for deals.

September Sales

Those trends already are putting a strain on Gap’s results. Same-store sales at Gap’s namesake brand slipped 3 percent in September, worse than the 1.7 percent decrease analysts estimated. Comparable-store sales have declined seven of the last eight months.

Last month, the retailer's Old Navy discount chain saw same-store sales rise 1 percent, while analysts estimated a 3.5 percent gain. Revenue by that measure at Banana Republic increased 2 percent, topping the 1.6 percent gain estimated by analysts.

Peck joined the company in 2005 and has held several brand, strategy and operational roles and also currently guides the company’s emerging Athleta, Intermix and Piperlime brands. He led the North American division of the Gap brand in 2011 and 2012, overseeing the colored-denim trend and was involved in Project Red, a collaboration with rock star Bono to fight AIDS in Africa through the sales of certain products.

“I’m passionate about product -- at our core, we’re a product company,” Peck said. “And I’m really passionate about digital and physical coming together.”

Outlet Business

Peck also oversaw the outlet business for the Gap and Banana Republic brands, opening locations overseas. His first role with the company was leading the development of its global strategy and establishing its first franchised markets.

“This is a planned and orderly process, and there’s a lot of continuity that’s going to come out of it,” Peck said in an interview. “We feel we have a very well-articulated strategy that’s delivering a lot of value and we’re a long way from being complete on. I’m committed to following that through.”

Peck’s compensation includes an annual salary of $1.3 million, options for 300,000 shares vesting over four years and annual performance bonuses targeted at 175 percent of his salary.

Murphy’s 2013 compensation was about $18.7 million, consisting of a $1.5 million salary, $14.2 million in stock awards, $2.7 million in nonequity incentive pay and about $351,000 in other compensation.

No Plans

Murphy said he has no plans for where he’ll go after the transition.

“Glenn Murphy is very well respected, there’s a lot of confidence in what he’s done so far and his vision for the company,” Betty Chen, a San Francisco-based analyst at Mizuho Securities, said in an interview. “There’s a little concern, even as they’re handing off the reigns to a very experienced executive and an insider.”

By Lindsey Rupp; editors: Nick Turner, Kevin Orland, John Lear.