Two oyster growers on Tasmania's east coast have stopped production after the discovery of a shellfish toxin in the area.

People have been warned not to eat wild shellfish from the Great Oyster Bay area on the east coast and Norfolk Bay in Tasmania's south.

The toxin was also detected at permissible levels at Greater Swanport.

Health authorities discovered the potentially fatal toxin during routine testing.

State manager for environmental health Stuart Heggie said no affected commercial product had been put out into the Tasmanian market.

"There are two growers who will no longer be able to harvest in the Great Oyster Bay area until those levels drop back down again," he said.

Impact on shellfish industry 'unknown'

Neil Stump from the Seafood Industry Council said it is too early to know the impact the discovery will have on the industry.

"At this stage it's very localised and will impact on the growers in the Great Oyster Bay area specifically," he said.

Authorities say it will be costly for the producers who have had to close down.

"They have to cease production and can't sell any product so it will impact directly on them," Mr Stump said.

"Other growers in the adjacent areas, where we've also detected the presence of this algae, are on a watch and alert at this stage."

Two oyster farms are expected to feel the pinch after ceasing operations over fears of toxin outbreak. ( ABC: Damian McIntyre )

Mr Stump said there have been no reports of anyone eating contaminated fish.

"They can still continue harvesting operations and sell to market, but most of them will be taking a very cautious approach to what they do going forward," he said.

The toxins are from the same type of algal bloom that forced a worldwide recall of east coast mussels two years ago, costing the state $23 million.

The warnings come in the midst of recreational scallop season and people are warned against eating wild fish from the affected areas.