Otago Fish & Game chief executive Ian Hadland said he hoped police had removed Gunn's firearms licence.
"Otago Fish & Game works hard to defend the sport but idiotic behaviour such as this doesn't make it any easier," Hadland said.
"This completely stupid behaviour reflects poorly on legitimate duck hunters."
Otago Fish & Game was still working with Central Otago police to ascertain if there were any other Wildlife Act offences committed, such as shooting from a boat under power.
On May 2, Gunn and a group of friends were duck-shooting off a boat on the Clutha River/Lake Dunstan near Butcher's Point when they spotted some ducks.
He fired six shots from a 12-gauge shotgun but unbeknown to him two women were walking on the track beside the lake.
They were partly obscured.
One was struck by shotgun pellets in the right leg and the other was hit in the right breast and collarbone area and received moderate injuries.