Shark cull activists have removed bait from drum lines in Western Australia's South West after the first shark caught on the line was killed on Australia Day.
A three-metre female tiger shark was shot four times in the head, dragged out to sea and dumped after being caught one kilometre off Meelup Beach less than a day after the drum lines were set.
The fisherman who took the tender for the South West said the shark was a threat to public safety and had to be removed.
"I'll continue to do it and then hopefully later we'll perhaps be able to take some samples or contribute in some way to knowledge and better understanding," he told Fairfax radio on Monday.
The fisherman, who has asked not to be named, said protesters had kept away from his vessel and he believed the shark died quickly.
"I was satisfied that I managed to get the rounds in the right place and we dispatched it as quickly as we possibly could," he said.
But West Australians for Shark Conservation president Ross Weir told AAP it was an inhumane way of killing the animal and about 22 activists were keeping an eye on the fisherman's activities.
"They have been out on the water and they have removed baits from the lines," he said.
Mr Weir said the fisherman did not have experience with sharks and his .22 rifle was not an appropriate gun.
Sea Shepherd Australia managing director Jeff Hansen said it was a cruel and painful death for the shark, which could have been stuck for hours.
"How can we condemn Japan for the indiscriminate killing of whales and dolphins, and do this to our precious protected marine life here in Australia?" he said.
"This method is utterly cruel and inhumane and these animals can take many hours to die."
The controversial program to kill sharks larger than three metres that came close to shore went ahead after federal environment minister Greg Hunt granted WA an exemption under the Environment Protection and Biodiversity Conservation Act, allowing the protected great white shark to be killed.
But the state government will be forced to use its own Fisheries Department officers in Perth after commercial operators pulled out following threats from activists.
Mr Hunt said last week that when the trial ended on April 30, a federal environment act assessment would determine if the policy should continue.
The policy was introduced after the death of Chris Boyd at Gracetown late last year, which was the seventh in WA since August 2010.
Premier Colin Barnett was heckled at an Australia Day event on Sunday, but brushed it off and said people were entitled to free speech.
The issue has also made international headlines and attracted anti-cull comments on social media from billionaire Sir Richard Branson and comedian Ricky Gervais.
A rally will be held at Cottesloe beach - the home suburb of Mr Barnett - on Saturday.
Thousands attended the previous protest.