Insurance adjuster Henry Liebman hauled in the shortraker near Sitka last month, the Daily Sitka Sentinel reported June 25.
Troy Tidingco, Sitka area manager for the Alaska Department of Fish and Game, certified Liebman's trophy catch and said it could be about 200 years old -- which would mean it was born about when James Madison was president.
Tidingco said the longevity record for shortrakers is 175 years, but that fish "was quite a bit smaller than the one Henry caught."
"That fish was 32 1/2 inches long, where Henry's was almost 41 inches, so his could be substantially older," Tidingco said.
Samples of the fish were sent to a lab in Juneau for an official determination, the newspaper said.
At 39.08 pounds, it broke the old record of 38.69 pounds for one caught on sport-fishing gear, the newspaper said.
"I knew it was abnormally big [but I] didn't know it was a record until on the way back we looked in the Alaska guide book that was on the boat," Liebman said.
Rockfish live at depths ranging from 84 feet to almost 4,000 feet. Liebman said he caught his at about 900 feet, 10 miles from shore.
Liebman plans to have it mounted.