Naim Kaoud, head of the Anbar province security council, said the militants attacked the fishermen's site in the early hours of Saturday, AP reported.
He added that three of the militiamen were wounded in a subsequent firefight.
A federal Iraqi security official, speaking on the condition of anonymity because of media regulations, confirmed the casualties.
Hundreds of Daesh terrorists have slipped into Iraq from Syria to link up with 5,000 to 7,000 militants already in the country. The militants are believed to be behind a string of ambushes, kidnappings and killings in the country.