Piracy and maritime crime are on the rise in the Gulf of Guinea, with 32 attacks off the Nigerian coast so far this year, Vanguard reported.

Pirates in West Africa who have relied on hijacking oil tankers to fund their criminal activities have been forced to adapt to cheap oil prices, switching to kidnapping for ransom as their main focus, ViceNews reported.

Nigeria loses more than $18 billion a year to oil theft, fraud and piracy in the country’s oil industry, according to Michele Sison, U.S. Deputy Ambassador to the U.N.

Nigeria is losing 400,000 barrels of crude daily to pirates in the Gulf of Guinea, depressed oil prices, corruption, and pipeline vandalism, according to London-based policy institute Chatham House.

As oil prices have fallen over the last two years, criminal operations that exploit the industry are also feeling the pinch.

In the first quarter of 2016, there were six known pirate attacks in the Gulf of Guinea and six attempted attacks — nine off the coast of Nigeria, one off Côte d’Ivoire, and two off Democratic Republic of the Congo. In 2015, there were 100 similar incidents in the Gulf of Guinea, according to Peter Wilson, U.K. ambassador to the U.N.

In 2015 a majority of the attacks were kidnappings rather than the oil tanker hijackings for cargo theft that accounted for the majority of piracy assaults in previous years. Oil tankers were targeted in just 18 percent of maritime attacks compared to more than 50 percent in 2014.

The shift in piracy tactics is likely due to Nigeria’s increased efforts to secure the waters off its coast and the fall in oil prices, according to Matthew Walje with Washington, D.C.-based nonprofit Oceans Beyond Piracy, which promotes long-term solutions to maritime piracy.

“A lower payout at the end made it so it was no longer an economically viable model,” he said. “So what they did instead was switch to a kidnapping for ransom model…. It takes just a few hours.”

Ramped-up patrolling of Nigerian waters and oil’s diminished profitability have made oil robbery too expensive.

Kidnapping is faster. Pirates storm a ship, identify who to take and what to steal, and then concentrate on evading security as they flee with hostages.

A disturbing increase in violence marked 2015 maritime assaults in the Gulf of Guinea, according to Oceans Beyond Piracy. Victims at sea have been beaten, tortured, starved and subjected to mock executions. New players are getting involved in piracy. Some of the gangs operating in the gulf are the same ones that have operated inside Nigeria, where kidnapping is a common crime, Walje said.

Despite increased piracy in West Africa, East Africa, once notorious for Somali hijackings, has seen a decline with just nine suspected piracy incidents in 2015. The decline can be attributed to a global and regional patrolling effort involving international naval ships, armed guards on private vessels, and a special court in the Seychelles established to try piracy.

The threat of piracy could grow as the shipping industry and international naval efforts in the region relax in the face of subsiding attacks, Walje warned. The naval presence in Somalia’s waters dropped 15 percent between 2014 and 2015, with commercial ships less likely to post armed guards on board.

Declining enforcement may encourage new offenders to try their hand at maritime crime, like authorities are seeing in the Gulf of Guinea.

It happened in Southeast Asia, where authorities grew complacent and piracy returned, prompting prevention efforts to kick back in force.