Eighteen months after 100,000 Murray cod fingerlings were released to help restock the river, initial results appear to be positive.

In February last year 50,000 fingerlings were released near Kingston and a further 50,000 at Swan Reach.

The releases were part of a restocking program by the Primary Industries and Regions South Australia (PIRSA) to bolster numbers in the river system.

The species is one of the largest native freshwater fish in Australia; a much-prized recreational catch and iconic species to the river.

It is also being threatened by invasive species of European carp.

The fingerlings were released to help restock the River Murray. ( Supplied: PIRSA )

PIRSA's Keith Rowling told ABC Radio Adelaide that juvenile fish believed to be from the fingerlings released had been spotted in the release areas.

It is hoped these fish will go on to rejuvenate natural stocks.

"All the fingerlings were tagged in a process called calcein marking, which basically puts a mark in the fish's ear bone," he said.

Mr Rowling said when the fish were caught or harvested by Fisheries, the ear bone could be removed and exact survival rates would be determined.

He said an estimated 5 to 10 per cent survival rate was expected.

"The stocking is one tool in the toolbox to support the conservation of the Murray cod and the recovery of the species."

Two more releases have been funded for early 2018.

Murray cod fingerlings being prepared for release. ( Supplied: PIRSA )

Mr Rowling said there had also been good signs that the natural population could be bouncing back.

He said he hoped the fish would once more be allowed to be caught for consumption.

"At the moment it is [only] catch and release," he said.

"The ultimate aim is to have a recreational fishery for this really important species."