The image of Tassal, Australia's largest salmon producer, has received another hit after an ethical superannuation fund divested itself of the company's shares.

Australian Ethical announced it has sold the shares mainly due to concerns about the sustainability of farmed salmon feed supply.

The company's head of ethics research Stuart Palmer said they were also concerned about the management of salmon farming in Macquarie Harbour on the state's west coast, including current legal proceedings against the Tasmanian Environment Protection Agency and the Tasmanian Government.

"There's a lot of very concerning matters being raised around the regulation of the harbour and aquaculture practices in the harbour," he said.

The superannuation fund, which holds the retirement savings of 30,000 Australians, held about $10 million of Tassal stock which represented between 1 and 2 per cent of issued capital.

A statement on the company's website said:

"Our view on aquaculture has been that it has the potential to reduce over-fishing and move towards a sustainable seafood production by substituting feedstock with plant based protein.

"Unfortunately, we believe Tassal and the salmon farming sector is not currently on track to achieve this goal."

Dr Palmer said the Australian Ethical will not be investing in any other salmon farming companies unless they reduce their use of wild fish as feed stock.