There was a flood of online speculation about how the 24-kilo blue marlin could have come to obtain the strange markings across its body after images were posted on social media.
But, now one of the fishermen involved has come forward to explain why it happened.
The fish, netted by fishermen from Lopez Jaena in Mindanao, Philippines, had bizarre markings that looked like letters had been tattooed onto the amphibious creature.
Pictures of the weird fish went viral after being posted online by stunned beachgoers, triggering bizarre speculation about what could have caused it.
Paranormal enthusiasts were quick to blame the markings on the supernatural and some even claimed aliens were trying to deliver a message, while others feared it was due to changes in Earth’s oceans.
GMA News said: “Whatever may the reason be as to how the fish got the design on its body, nobody knows. But maybe, it is a sign perhaps that something is wrong with our ocean.”
Missinggalacticfreedom.wordpress speculated: “How this fish got symbols, letters, numbers, etc in his body remains a mystery but could it be that the fish was sent by something supernatural to deliver a message to humanity?
“Can you decipher it?”
Even alien hunters got involved.
Scott C Waring, editor of ufosightingsdaily.com, is quick to blame any mystery at the door of alleged alien visitors.
He blogged: “This large fish may have been a visiting alien species that wanted to mingle with a species similar to its own, only to get caught and eaten as food.”
However, fisherman Zosimo Tano, 41, has since come forward.
He caught the fish and explained how it received it’s “markings”.
Mr Tano said he had wrapped the fish in his printed T-shirt and the image had been reversed onto the marlin.
He told ABS-CBN News: “It has no tattoo I never thought that the print of what I used to cover would embed on the fish skin.”
To prove it, he also showed the T-shirt with the matching print.
He later sold the fish, which was his only catch of the day.
The Bureau of Fisheries and Aquatic Resources (BFAR) said there was a chemical reaction between the fish’s slimy skin and the print of the fabric that required further study.