Shocking twist as the man who first tamed Gus the Blue Groper makes a bombshell claim after the spearfisherman was pictured proudly showing off his prey

The big blue fish illegally killed at a Sydney dive site was not the locally famous Gus the Groper, says the man who first tamed and named it.

76-year-old wildlife documentary maker David Ireland first befriended the beloved giant in the 1980s when he ran a nearby dive shop and filmed underwater adventures for TV.

He built a level of trust with the fish that lasted decades, with Gus being able to immediately pick him out from the crowd and run up to him for a hug as soon as he saw the filmmaker.

Mr Ireland spent hours capturing footage of himself with Gus as he swam, petted and fed sea urchins in the waters off Cronulla, in Sydney's south.

Locals feared Gus had been killed when, on December 30, a spearfisherman was seen carrying a dead bluefinger out of the water at Oak Park Beach, where Gus lived on a nearby reef.

The fisherman, believed to be a New Zealander, was later fined $500 by police, and a further $300 by the NSW Department of Primary Industries on Friday, for spearing the protected species.

But on Tuesday, Mr Ireland told Daily Mail Australia: 'That wasn't Gus.'

David Ireland says the big blue wrasse illegally killed at a Sydney dive site (pictured) wasn't the famous Gus that locals feared

He said that Gus was much larger than the fish depicted with the spearfisherman, and that he also had a noticeable scar near his tail, where he had been speared years earlier but had survived.

“I go way back with Gus to when I first started teaching diving before we had a boat,” he revealed.

'Gus' territory was the first reef outside the beach – it extended about 150-200 meters. I held a sea urchin upside down and he darted over to me and picked it up.

'After a while he got so used to me that as soon as I arrived, even among four divers, he could pick me out no matter what wetsuit I was wearing.

'I don't know how he did it.

“Eventually he was so tame that I could put my arms around him like a puppy and pet him.”

He added, “I called him Gus, and that went on for decades.

“Every time I dived, I held Gus and fed him and then I filmed (myself) introducing him to my son Jason 11 years ago.

“I knew him very well – and the fish that idiot killed was not Gus.”

David Ireland spent hours shooting footage of himself with Gus as he swam, petted and fed sea urchins in the waters off Cronulla, in Sydney's south

David Ireland filmed how his son Jason (pictured) was introduced to Gus eleven years ago

David Ireland bonded with Gus by feeding him sea urchins (pictured)

During that filming session, the father of four saw the injury from Gus' previous encounter with a spearfisherman.

“All the probes are subtly different – they have slightly different markings, shades of blue, etc.,” Mr Ireland said.

“But on that trip with Jason in 2013, I noticed that Gus had been impaled at the base of the tail and there was a nasty wound there.

“I hoped it would heal, and it did, but it left a notch at the base of the tail, so that made it very easy to identify, even for anyone who didn't know it as well as I did.

“But I knew Gus from behind – and that wasn't him who was killed by the spearfisherman.”

Mr Ireland has slammed the man who murdered the payers – who are protected from spearfishing due to their friendly nature – at Christmas.

“There's always idiots everywhere, aren't there?” he exploded. 'He clearly knew what he was doing – he had a decent wetsuit and good quality equipment.

'He had clearly done it before and he must have known what he was doing was illegal. There would have been no question; they are so friendly, it would have swum straight to him.'

Locals say there are between seven and 10 blue gropers in the reefs around Oak Park and Mr Ireland believes it was probably one of the other younger fish that were killed.

“It's more than likely one of Gus' descendants,” he said.

'It was I who tamed Gus. It was me who mentioned Gus. You have all these so-called experts coming out of the woodwork, they know nothing.”

The fisherman, who was reportedly from New Zealand, strode into the water and speared the blue groped

The spearfisherman slung the fish over his shoulder as he marched onto the beach and then walked away from shore with the fish in his arms, but told police he had been put 'back in the water'.

Amazed locals watched as the man slung the fish over his shoulder and carried it onto the beach, reportedly hurling 'abuse' at onlookers

The NSW Department of Primary Industries confirmed they had managed to trace the spearfisherman and officials fined the 26-year-old an additional $300 on top of the $500 police fine.

Natalie Williamson, one of the witnesses who saw the man emerge from the water with the dead fish, said he began shouting at bystanders when they challenged him.

And she condemned the fines handed out as too small for killing such a large fish.

Spear grabs in NSW carry a fine of up to $22,000, but the spear fisherman escaped by paying just a fraction of that.

“It's not much at all,” she told Daily Mail Australia. “I'm not sure the fine will stop him from doing something like that again.”

A DPI spokesperson said the spearfisherman had shown remorse after fisheries officials caught up with him.

“The individual in question showed great remorse for his actions during the interview with NSW Fisheries Officers,” she added.

'It was the Person of Interest's first fishing offence.

“Fisheries officials have also provided the individual with educational and awareness materials to ensure he knows and understands the rules of spearfishing.”