TAMPA — If you tread water too long in the same spot, someone might start asking why you’re not trying to swim somewhere.Tampa’s Bloomin’ Brands — parent company of such prominent restaurant chains as Outback Steakhouse, Carrabba’s Italian Grill and Bonefish Grill — has been treading water the past few years with flat restaurant sales and a lukewarm share price. Recent earnings fell sharply.On Monday, investor Barry Rosenstein, principal owner of New York hedge fund Jana Partners, launched an activist campaign at Bloomin’ Brands. Jana stated in a securities filing that Rosenstein may urge Bloomin’ to consider "exploring a sale" of the business. To back up that suggestion, Jana spent nearly $140 million on Bloomin’ Brands shares, taking an 8.74 percent stake in the company. Jana describes itself as a firm that invests in "companies undergoing or expected to undergo change."Bloomin’ shares awoke to the news Monday, rising more than 12 percent. Company shares closed at $20.54, a 12.42 percent gain for the day.Bloomin’ Brands is one of Tampa Bay’s larger public corporations, a major employer and one of the better known companies by the general public. Its CEO is Liz Smith.(Bloomin’ Brands on Tuesday acknowledged the new stake in the company in a brief press release. "The board of directors and management appreciate the views of its stockholders and will consider the perspectives reflected in the Schedule 13D (regulatory filing by Jana). The Company has and will continue to serve the interests of all stockholders.")RECENT COVERAGE: Tampa parent of Outback, Carrabba’s still struggling amid glut of restaurants. Another water-treading Tampa Bay company — TV/online retailer HSN — was purchased earlier this year by the parent of competitor QVC. In its regulatory filing, Jana said Bloomin’ Brands shares were "undervalued and represent an attractive investment opportunity." Jana said it expects to have discussions with Bloomin’s management and board of directors and shareholders among other interested parties.Jana Partners is not new to the activist investor game. Earlier this year, the firm took a stake in Whole Foods Market, pushing it to explore options.Jana’s Whole Foods’ proved to be a big winner when Amazon opted to buy the organic grocery chain.Contact Robert Trigaux at [email protected] Follow @venturetampabay.