Pirates in the Gulf Of Aden will have an armed Royal New Zealand Navy frigate to contend with when the HMNZS Te Mana joins international anti-piracy efforts.

Commander Shane Arndell is leading his crew of 177 people on the eight-month deployment around the Horn of Africa.

The ship, one of just two frigates in the New Zealand Navy's combat force, left the Devonport Naval Base on August 12 to begin the mission with a training period in Australia.

Defence Minister Jonathan Coleman says piracy in the Gulf of Aden and the Indian Ocean region affects all countries with shipping trade going through the Suez Canal.

"New Zealand has a direct interest in supporting the maritime security taskforce and protecting shipping lanes with a large volume of our trade carried by shipping."

It is the first time since 2008 a New Zealand frigate has been deployed to the region.

The route is one of the busiest and most important to maritime trade in the world.

Piracy has decreased over the past five years thanks to a multi-national maritime security taskforce. The IMB Piracy Reporting Centre says the number of incidents has fallen from about 406 in 2009 to 297 in 2012.

Pirates usually attack off the northern Somali coast in the Gulf of Aden and the Southern Red Sea.

They fire automatic weapons and rocket-propelled grenades at merchant vessels in an attempt to board and hijack the ships. They then demand a ransom for the release of the vessel and the crew.

Many merchant and passenger cruise ships now carry armed security guards in this region.

Te Mana will remain in the anti-piracy operation over the Christmas and New Year period, returning to New Zealand in March 2014.

Commander Arndell says the deployment shows New Zealand is playing its part as an international citizen.