* Piracy attacks are down due to vigilance
* But 177 seafarers still held hostage
* Risk of further attacks remains
LONDON, Sept 12 (Reuters) - Somali pirate activity is expected to stay low despite the end of the monsoon season, as aggressive navy action, private armed security teams and defensive measures by ships keep the heat on gangs at sea, navy and security officials say.
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 with 163 in the same period last year, International Maritime Bureau data showed.
"We are expecting the activity rate to be lower than last year at this time ... that is based on the lack of activity in the past six months," said Commodore Bruce Belliveau, NATO's Deputy Chief of Staff Operations.
"We are not seeing the build up of logistic supplies that they would have had in the past for outfitting fishing vessels or dhows to use as motherships," he told Reuters on the sidelines of a shipping conference in London on Wednesday.
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.
"In previous years, pirate attacks had jumped by around 70 per cent after the monsoon season ended. However, the post-monsoon jump will be far less," said Rory Lamrock, an intelligence analyst with security firm AKE.
"Ships are better secured and naval operations have put more pressure on pirate groups, to the extent that the chance of a successful hijacking is now very slight compared to years gone past. This has made Somali piracy an increasingly unattractive criminal enterprise."
NATO's counter piracy mission is among efforts by international navies to combat the seaborne menace, but officials acknowledge that resources are limited.
Belliveau said forces covered 11 million square km (4 million square miles).
"It's a huge area to patrol," he said.
"It's not irreversible - the success that we are enjoying right now. If we let down our guard, if we reduce the level of forces, if we reduce the compliance ... then we will create a new opportunity for entrepreneurial pirates to come back."
Belliveau said there were 177 hostages and seven vessels held, compared with 682 seafarers and 30 ships held in February 2011.
Somalia's poverty and anarchy make the prospect of million-dollar ransoms still attractive despite the risks. Last week, suspected pirates opened fire on an Italian navy helicopter off the coast of Somalia, wounding a pilot.
AKE's Lamrock said the incident "hints at the increasing desperation of pirate groups".
"It may also have been a hostile reaction following on from the EU's helicopter-borne attack on a pirate logistics stockpile earlier this year," Lamrock said.
Belliveau said the election of Somalia's new President Hassan Sheikh Mohamud was a "positive step forward".
"There is an insurgency going in southern Somalia with al Shabaab - there are a host of issues that the government will have to deal with," he said. "It will take them time to build institutions, but it's a step in the right direction and provides some hope for the people of Somalia."
Mohamud and the visiting Kenyan foreign minister escaped an apparent suicide bomb attack on Wednesday that was claimed by al Shabaab rebels. (Editing by Robin Pomeroy)