"We think it will act both as a deterrent and also [provide] some immediate capacity to follow on and pursue pirates, if we can catch them," Ripert said.
However, the issue of who has jurisdiction over captured pirates and where they can be prosecuted remains unresolved.
The European mission is aimed at protecting ships that carry World Food Programme supplies to feed about three million Somalis who depend on food aid, as well as escorting shipping frigates in the area.
The naval force, backed by patrolling aircraft, will be commanded by British forces.
There have been about 95 pirate attacks in Somali waters this year, with about 40 ships captured, including a Saudi tanker holding $100 million of oil.
There are already several international naval operations along the Horn of Africa, including a Nato mission to counter piracy, but they have done little to deter hijackers, who have been paid tens of millions of dollars in ransoms by firms seeking to free hijacked ships.