DES MOINES — A fisherman died Friday while on a boat in a southern Iowa lake, authorities said.

The Appanoose County Sheriff’s Office said the 79-year-old man died on Rathbun Lake, about 90 miles southeast of Des Moines. Authorities received a report of an unresponsive person in the water around 1:45 p.m. near the lake’s Island View Boat Ramp, according to the Des Moines Register.

Witnesses said they had seen the man fishing on a boat, then five minutes later noticed him floating in the water unresponsive, according to a news release.

Nearby boaters attempted to revive the man. Emergency personnel brought him to the boat ramp and tried other life-saving measures, but he was pronounced dead at the scene, the news release said.

The name of the fisherman was being withheld until relatives were notified. The news release said the state medical examiner will conduct an autopsy. It did not list the cause of the man’s death.