A fish farm in Tasmania’s Macquarie Harbour can now restock, after it was shut down due to environmental degradation.

Tassal was made to remove fish from its Franklin lease, which borders a World Heritage Area (WHA), after it was linked to a significant decline in the number and range of organisms.

Petuna, which operates the Franklin lease with Tassal, says the Environment Protection Authority (EPA) has approved the restock, which will be carried out under a new stocking plan.

“Our alternating stocking plan will see smolt placed on the southern leases for a shorter time period of 9 to 10 months, before being moved to the northern leases in the Harbour where they will continue to grow to harvest size,” Petuna CEO Ruben Alvarez told the ABC.

“This will allow the more sensitive southern leases at Franklin and Bryan's Bay to be rested for at least 15 months before the next group of smolt are transferred, giving more time for sediments within the leases to recover naturally.

“This is a material shift in how farms in the harbour have been managed in the past and will achieve significant biosecurity and environmental improvements in the long term.”

Environment Tasmania says all salmon companies have to let the harbour recover.

“There is a small increase in marine life that's returned to the lease but it's dominated by the worm-like creatures that feed on salmon waste,” she said.

“We're seeing small signs of recovery, but still really worrying signs with gas bubbles, bacteria and poo-eating worms dominating the marine life recovery.

“Why on earth you'd turn around and say that's good to go, is just baffling.”