Beach-goers reportedly booed a Kiwi accused of illegally killing a beloved Sydney fish as he attempted to shove its body into a supermarket bag before carrying it up the sand. 

Sydneysiders had earlier expressed anger the 26-year-old was fined just NZ$859 (A$800) for killing what most believe was a blue groper, called Gus. 

Gus had become a marine celebrity for his friendliness as he swam alongside divers off the coast of Cronulla in the city’s south. 

Spearfishing blue gropers is also illegal in New South Wales, with a maximum fine is A$22,000 or six months in prison. 

Authorities who fined the man - who has not been identified - said he showed “significant remorse” when confronted by fishery officers. 

But local woman Natalie Williamson has told media outlet Daily Mail she called police after watching the incident and said the fisherman didn’t appear sorry at the time. 

She said locals started booing the man, who responded by calling them “rednecks”. 

“He neglected to see any of the massive signs that says no spearfishing and when confronted by locals within minutes of pulling the fish out,” Williamson told the media outlet. 

“There was no remorse (at the time). 

“He was straight on the defence and spent ten minutes sitting on the rocks with it before trying to fit it into a Coles bag, then couldn’t, and walked back up the shore carrying it having everyone watch him.” 

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Photos shared widely on social media show the man in a wetsuit triumphantly holding the slain groper. 

Earlier, an online petition started by the New South Wales Animal Justice Party demanded justice for the beloved fish and protection for other gropers living in the local marine environment. 

A 26-year-old Kiwi was fined more than $800 for allegedly killing a protected groper called Gus in a Sydney marine reserve. 

“Gropers are our state fish. They are supposedly protected by law from spearfishers, but the law did not protect Gus,” wrote a party spokesperson. 

“What is even more enraging is that even though the man who killed Gus was caught, the A$800 fine he received was woefully inadequate for the violent and deliberate act. He not only illegally speared Gus, a protected species, but he did so in an area designated as a no-spearfishing zone”. 

“Gus didn’t see humans as a threat, he may have swum right up to his killer expecting a pat but instead, he was shot with a speargun in a callous, cowardly, and illegal act,” the petition reads. 

Locals saw the man, his wetsuit stained with blood, posing for a trophy picture with the slain blue groper in Sydney. 

A NSW Department of Primary Industries spokesman said the fisherman regretted his actions during an interview with fisheries officers. 

It was also his first offence and they provided him with educational material to understand the rules of spearfishing. 

However, in a shock claim, wildlife documentary maker David Ireland told the Daily Mail Australia the dead fish is not, in fact, Gus. 

Ireland said Gus was bigger than the fish shown in photos and also had a distinctive scar on his tail from a previous spearfishing encounter. 

The 76-year-old ran a nearby dive shop and befriended the fish in the 1980s when he was teaching diving. He said Gus was able to instantly pick him out from other divers. 

Wildlife documentary maker David Ireland claims Sydney's blue groper Gus – pictured in happier times – is likely still alive. Photo / Abyss Scuba Diving 

“Eventually he was so tame, I could put my arms around him like a puppy dog and pat him... I named him Gus, and that went on for decades,” Ireland told the news outlet. 

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

The spearfisher was initially questioned and fined A$500 by New South Wales state police for fishing in a no-fishing zone. 

There were seven to 10 groper living in the area and the dead fish was likely to be one of Gus’ offspring, Ireland said. 

He had choice words for the spearfisherman, saying there were “always f***wits everywhere”, and the man’s wetsuit and gear showed he knew what he was doing and must have known it was illegal. 

But there would have been no sport in the kill as blue groper were so friendly the fish had likely swum right up to the man. 

“It was me who tamed Gus. It was me who named Gus. You’ve got all these so-called experts coming out of the woodwork – they know nothing.” 

Residents have proposed the area at Oak Park where the groper was killed should be named Gus Reserve as a tribute.