Mr Long had helped build a hunters' hut on the island with his father and was a keen deer stalker.
He was alone when he was shot.
The New Zealand Herald reported Mr Long had often helped out with pest control and other club initiatives.
He also helped build the Martins Creek Hunters Hut on Stewart Island.
New Zealand Deerstalkers Association Southland branch member Neville Miller said the group were "absolutely bloody gutted" after Mr Long's death.
Fellow member Douglas Gordon said Mr Long and his dad Steven had a close association with the hunting club.
"They are both good members of the club and good members of the executive. It will be a sad loss," Mr Gordon said shortly after Mr Long died.
On Mother's Day, two people died in separate hunting accidents.
Early on Sunday morning, 15-year-old James Ross Bucko Johnston, from Whakatane, died while out duck shooting.
The Trident High School student, known as Jamie, was hunting with two other teenagers and a parent at Matata, near Whakatane.
The firearm he was using discharged and he died at the scene.
Jamie's father Colin "Bones" Johnston described the incident as a "tragic accident".
The school principal said Jamie was a "well-loved, respected student, friend and sportsman."
Later on Sunday, 21-year-old Joshua Hill was shot and killed while hunting in Ruatiti, near Raetihi.
Police believed Mr Hill's gun went off as he crossed a fence.
Mr Hill was an aircraftman in the Royal New Zealand Air Force. Family described him as a keen golfer, rugby player and hunter with a "cheeky smile".
Nicole McKee, New Zealand mountain Safety Council programme manager for firearms and hunter safety, said both deaths were unnecessary and tragic.
She called the incidents "devastating for the firearms community but especially for the families of those involved."
The recent hunting deaths have prompted a Government safety review.
"Unfortunately there seems to be an increasing frequency of firearm incidents causing injury or death. The worst aspect is that these incidents are largely preventable," Associate Conservation Minister Peter Dunne said yesterday.
Mr Dunne said he was starting a review "of unsafe and illegal gun use in the outdoors."
He said the review would establish what the problems were, where responsibility might lie, and what could be done to reduce the risks of death and injury from improper gun use.
