A new report on piracy has some encouraging news: Piracy at sea has reached the lowest levels in six years, with 24 attacks against merchant ships recorded worldwide in 2013, a 40 percent drop since Somali piracy peaked in 2011. Fifteen incidents were reported off Somalia last year, compared to 75 in 2012 and 237 in 2011. Only two vessels were hijacked last year, and both were quickly released.

Contributing to the decline have been the presence of armed guards on merchant ships, international navy patrols, beefed up onboard security measures and “the stabilizing influence of Somali’s central government,” according to the annual global piracy report by the International Maritime Bureau (IMB) in London.

But no one is declaring victory.

While the report documented a decline in attacks off the Africa’s east coast, mostly in the Gulf of Aden’s busy shipping lanes that link Europe with Africa and Asia, there’s been a surge in incidents off Africa’s west coast, mostly in the oil-rich area of the Gulf of Guinea, near Nigeria.

Piracy off the west coast of Africa, which has a long history of at-sea crime, accounted for 19 percent of all global incidents, with Nigerian bandits being the most active, responsible for 31 of the region’s 51 incidents.

Crimes have become more violent, moving from thefts on berthed ships and armed robberies of fishing boats, to violence against cargo ships by armed gunmen who last year killed one crew member and kidnapped 36 people who were held for ransom — the most since 2008. The Nigerian pirates moved far into waters off Gabon, Ivory Coast and Togo, where they were responsible for at least five of the region’s seven reported hijackings. Their favorite targets were valuable oil tankers.

There are important differences between piracy off the east and west coasts of Africa. Local governments are largely functional in the west and can defend their shores against piracy by patrolling their own territorial waters 12 miles offshore, where most of the attacks occur.  They also have courts to try the pirates and prisons to detain them. As a result, finding a resolution for piracy does not involve warships, but shore-side actions, such as strengthening West African governments so that they have strong laws and naval forces.

Off Somalia, by contrast, where there is no functioning government and attacks occur hundreds of nautical miles from the coast, international navies have intervened under a 2008 U.N. resolution.

Despite the drop in documented attacks off Somalia, international governments and the world shipping community should not let their guard down. “It is imperative to continue combined international efforts to tackle Somali piracy. Any complacency at this stage could re-kindle pirate activity,” Pottengal Mukundan, director of the IMB, said in a statement. The IMB’s Piracy Reporting Centre has monitored piracy since 1991. “The risk still remains in Somalia. On Dec. 9, there was an unsuccessful attack, so the pirates are still there,” he said.

Another hijacking by Somali bandits — the first this year — was deterred on Jan. 17 by an armed security team onboard a merchant vessel near the port of Salalah, Oman.

The most pirate attacks of 2013 occurred in Indonesia, accounting for more than 50 percent of all incidents. Armed robbery on these vessels increased for the fourth consecutive year. But the report called these “low-level opportunistic thefts, not to be compared with the more serious incidents in Africa.”

Attacks were also up in India and Bangladesh, reaching 14 last year.

What’s ahead for 2014?

“It’s difficult to predict and will depend on geo-political factors onshore in all those coastal states,” Mukundan said in a video interview posted on the IMB website. “But it’s important to highlight that we still have 64 crewmembers (still being held hostage) in Somalia, some for two or three years,” he said. “We need to bring them out.”