Clean Seas announced yesterday it would write down its mulloway inventories by $2.2 million to $4.3 million, its kingfish inventories by $4.9 million to $38.2 million, and write off $1.2 million spent on new market entry costs.

The company said it was "clearing the decks" for the new financial year to set it up for the commercialisation of southern bluefin tuna.

Chairman Hagen Stehr said the company would be increasing its focus on producing southern bluefin tuna due to the considerably better margins available in the medium term.

He said Clean Seas has an over production of kingfish and will divert some of its kingfish and mulloway resources towards the tuna, and lower kingfish production from 1.25 million to 1 million fingerlings to ensure the tuna division operates without capacity limitations.

"Our kingfish sales are going up, but not as fast as we'd like," he said.

The oldest of the first southern bluefin tuna the company reared are now 125 days old and 30 centimetres long.

Clean Seas is still on track to produce about 25,000 southern bluefin tuna fingerlings for commercial grow out late this year, or early in the new year, but a lot will depend on whether it can get a new hatchery built in time.

The company said it has made advances with its pellet feed trials that have been conducted off Port Lincoln.

The first trial using Hayashikane Sangyo/Ridley pellets for 3-year-old fish has achieved a 4:1 food conversion ratio, which is a good result for fish of this age.