NSW and South Australia have placed a precautionary ban on the importation of oyster seed stock from Tasmania.

Biosecurity Tasmania and Oysters Tasmania are investigating after the oyster grower observed an above average mortality rate at the lease last week.

POMS only impacts oysters. It does not have health implications for humans.

There are no restrictions on harvesting oysters for human consumption in relation to POMS, but there are industry-imposed restrictions on movement of oysters for stocking on to farms.

Tasmania's chief veterinary officer Dr Rod Andrewartha said the Pitt Water oyster grower pursued measures to identify the cause of increased mortality and minimise industry impacts.

"Although this virus is not a threat to public health, it does have a severe impact on oysters so Biosecurity Tasmania is working closely with the grower and industry to identify its distribution and put in place measures to minimise its further movement," Dr Andrewartha said.

"Pacific Oyster Mortality Syndrome is a virus that is generally spread through the oyster product or items that have been in contact with infected product."

POMS was first identified in Australia in NSW in 2010.

Consequently, movement restriction was placed on oysters and oyster products to reduce the risk of POMS spreading.

Dr Andrewartha said other oyster growing leases were being observed and Biosecurity Tasmania would continue to investigate.

Industry spokesperson Neil Stump said although the disease was a concern for producers, healthy oysters could still be harvested and product being sold through retail outlets was safe to eat.