Mack the Knife had been known by a variety of names by visitors
The star attraction at an aquarium in Greater Manchester has died.
Mack the Giant Green Knifefish was 4ft (1.2m) long and Bolton Museum, Aquarium and Archive's most popular exhibit.
The fish had been at the council-run aquarium for about 10 years and was thought to be aged about 13 when he died from natural causes.
Mack was believed to be the largest of its species in the world and the only one living in captivity in the UK, Bolton Council said.
Over the years the fish had been given a variety of names by visitors, including Sparky, Kevin and more recently Mack the Knife.
Mack arrived at the aquarium in 2000 as a rescue fish when its previous owner found it too big to keep.
Giant Green Knifefish are usually found in Venezuela and do not normally live as long in the wild as they do in captivity.
Executive Member for Adult and Community Services, Councillor Elaine Sherrington said: "Mack the Knife was a great asset to the aquarium and will be missed by the public and staff alike.
"He'd had a good life in Bolton, attracting many visitors, and staff were quite sad to learn the news of his death as he had been here for so long."