Tasmanian salmon farmer Huon Aquaculture has begun stocking its offshore "fortress pens" with millions of Atlantic salmon, reports ABC News.

Some 2.2 million 500-gram fish are being transported to the new site in Yellow Bluff from the company's hatchery via the wellboat Ronja Huon.

"After about eight months they'll be transported to 11 larger pens at Storm Bay," said David Moorehead, general manager of Huon Aquaculture's marine operations.

This allows the company to keep the different sizes separated in different locations.

"It also allows us to fallow Yellow Bluff before we then stock it next year," he said, a move expected to help protect against disease.

The special fortress pens operate in sea heights of up to six meters in the open waters of Storm Bay.