BAGHDAD — ISIS earns millions of dollars a month running car dealerships and fish farms in Iraq, making up for lower oil income after its battlefield losses, Iraqi judicial authorities said on Thursday.

Security experts once estimated the terrorist group’s annual income at $2.9 billion, much of it coming from oil and gas installations in Iraq and Syria.

The U.S.-led coalition and Russian campaign have targeted ISIS’s financial infrastructure, using air strikes to reduce its ability to extract, refine and transport oil and so forcing fighters to reportedly take significant pay cuts.

Yet the militants, who seized a third of Iraq’s territory and declared a caliphate in 2014, seem to be adapting again to this latest set of constraints, in some cases reviving previous profit-turning ventures like farming.

“The terrorists’ current financing mechanism has changed from what it was before the announcement of the caliphate nearly two years ago,” a report by Iraq’s central court of investigation said, quoting Judge Jabbar Abid al-Huchaimi.

“After the armed forces took control of several oil fields Daesh was using to finance its operations, the organization devised non-traditional ways of paying its fighters and financing its activities,” the report added, using an Arabic acronym for Islamic State.

Fishing in hundreds of lakes north of Baghdad generates millions of dollars a month, according to the report.

Fish farms have supplied militants with income since 2007 when ISIS’s al-Qaeda predecessor fought U.S. occupation forces but the mechanism only came to the authorities’ attention this year, the report said.

The militants also tax agricultural land and impose a 10 percent levy on poultry and other duties on a range of imports into their territory, it added.

New revenues are also being generated from car dealerships and factories once run by the Iraqi government in areas seized by the militants.

Those have helped offset the losses from lower oil income, though perhaps only partially. The U.S.-based analysis firm IHS said last week that ISIS revenues had fallen by around a third since last summer to around $56 million a month.