* Somali piracy more than halved in first six months
* Naval action and use of security guards paying off
* Global piracy down one-third, West Africa a concern
By Jonathan Saul
LONDON, July 16 (Reuters) - Tougher action by international navies and the use of private armed guards on ships have more than halved the number of Somali pirate attacks, the International Maritime Bureau (IMB) said on Monday.
Last year, Somali piracy in the busy shipping lanes of the Gulf of Aden and the northwestern Indian Ocean netted $160 million, and cost the world economy some $7 billion, according to the American One Earth Future foundation.
But in the first half of 2012, there were just 69 incidents involving Somali pirates, compared to 163 in the same period last year, resulting in a decline of a third in piracy worldwide.
International navies have stepped up pre-emptive action against pirates, including strikes on their bases on the Somali coast, and shipping firms are increasingly using armed guards and other measures such as heightened watches and razor wire.
"The naval actions play an essential role in frustrating the pirates. There is no alternative to their continued presence," said IMB director Pottengal Mukundan.
The IMB, which has been monitoring piracy worldwide since 1991, said the number of reported pirate attacks fell to 177 in the first six months from 266 in the same period last year. Still, most involved the use of weapons.
Somalia's widespread poverty and anarchy continue to make the prospect of landing million-dollar ransoms attractive to many young men, and the pirates currently hold more than 300 hostages of various nationalities.
"There is a risk that if security standards on board merchant vessels start to slip, pirates will once again start to take advantage of unprepared vessels off the Horn of Africa," said Rory Lamrock, an intelligence analyst with security firm AKE.
Meanwhile, piracy is on the increase on the other side of Africa in the Gulf of Guinea, an increasingly important source of oil, cocoa and metals for world markets.
The IMB said 32 incidents, including five hijackings, were reported in the area in the first six months of 2012, up from 25 in the first half of last year. More than half involved weapons.
In Nigeria alone there were 17 incidents, up from six. Togo had five, compared with none in the first half of 2011. (Editing by Kevin Liffey)