THE state's peak fishing body has called for a moratorium on the expansion of kingfish farming until the number of juveniles escaping and devastating other species can be reduced.

Primary Industries and Resources SA has confirmed about 7500 juvenile kingfish have escaped from farms at Arno Bay, north of Port Lincoln, and in Fitzgerald Bay, near Whyalla.

Fishing experts believe the number is '10 times that figure' in the past year with severe damage to the ecology of many sensitive locations.

The predatory kingfish have spread throughout Spencer Gulf with large numbers now present along the gulf from Port Lincoln to Whyalla and down to Wallaroo on Yorke Peninsula.

The juvenile kingfish - ranging in size from 30cm to 65cm - have escaped from the fish farms when nets are changed or when sharks damage the enclosures.

The kingfish are cutting a swath through delicately balanced estuaries and fish nurseries, devouring large numbers of juvenile whiting, squid, garfish and tommy ruffs.

One 50cm kingfish caught at Tumby Bay on eastern Eyre Peninsula last week had six 15cm king george whiting in its stomach.

South Australian Recreational Fishing Advisory Council executive officer Trevor Watts said it was suspected the actual number of escaped fish was greater than admitted figures.

'We have just been given information that there have been considerable numbers of escapes from Arno Bay and Fitzgerald Bay,' he said.

'We feel there should be a moratorium on any future development until such time as the management practices have been further tightened to prevent escapes.

'There has been an explosion in numbers of juvenile fish and we view the numbers of fish that are escaping with some concern. When people admit to something it is usually on the lower scale.'

PIRSA Aquaculture general manager Ian Nightingale said yesterday meetings with kingfish farm operators had been held in September and they had reviewed their practices.

'A lot of new conditions regarding their farm management practices have been in place since November,' Mr Nightingale said.

A research project also had been initiated to examine the kingfish farming industry and its interaction with the wild population.

Whyalla charter boat operator and tackle store owner Robert North said juvenile kingfish were now in plague proportions.

'In some places you cannot catch a squid because they have all been eaten,' he said.