San Diego residents were in awe when Mike Livingston of Central California caught the giant fish.
Livingston caught the yellowfin on Nov. 30 on a sailing trip in Mexico. Livingston's previous big fish was a 100-pound yellowfin.
The International Game Fish Association still has to confirm the weight. If it stands, it would break the record for the biggest tuna ever caught, which weighed in at 388 pounds.
The Associated Press contributed to this report.