A plan has been drawn up to cut the number of permits for great white shark cage diving tours off the South Australian coast.

Research has found the sharks' behaviour has changed.

The Neptune Islands near Port Lincoln are the only place in Australia where tourists can dive in cages to view great white sharks.

Four operators are licensed to conduct tours, but only two are allowed to use berley to attract the sharks.

CSIRO scientist Barry Bruce says the use of berley has more than doubled in the past four years and that is changing the sharks' behaviour in the waters off Eyre Peninsula.

"Sharks are now staying for longer periods, they're residing at the Neptune Islands for longer periods," he said.

"When they are there, they're spending more time in close to the coast of the Neptune Islands where the shark cage operations occur."

He says the sharks could be at risk if they become distracted from searching for their food supply.

CSIRO research of the waters around the Neptune Islands showed berley was used 270 days per year, more than double the rate of a few years ago.

When a fifth tourism operator sought to enter the industry, South Australia's Environment Department decided it was time to take stock.

It wants to cut the number of tour licences to two and limit the number of days the tours can operate.

It is keen to impose a limit of 200 days annually.

Official Barry Hayden says that would help protect the species.

"In some ways it's making some tough decisions now for the benefit of the industry in the long run," he said.

The department is consulting about the policy proposal.

In South Africa, where the industry is booming, some surfers say berleying by tour operators has turned them into bait for sharks attracted to those areas.