The brand will be promoted by the Fish Marketing Organisation. To be registered under the scheme, fish farms will have to meet several requirements governing such areas as size of ponds, drainage, source of water and precautions against red tides.

They will have to inform the Agriculture, Fisheries and Conservation Department within 14 days of buying fish fry, after which the department will regularly check hygiene and use of medicine and feed as the hatchlings grow.

A drug-residue test will be needed before the fish are sold.

Farms that breach the guidelines will be deregistered.

Fish being sold under the new brand will be identified, possibly with tape on their dorsal fins.

Local fish products have difficulty competing with mainland imports. For example, the market price of mainland mullet is $10 to $12 a catty, compared with $16 a catty for local mullet.

So far about 30 of the city's 1,450 fish companies have agreed to join the scheme.

The government has promised to provide technical assistance for small-scale companies that want to join.

Companies believe it won't cost them much more.

'We believe the cost of feeding fish after joining the scheme will increase by only 10 per cent because we have adequate facilities,' said Yeung Sui-leung, director of Yeungs Marine Products, the first company to join the scheme.

'We need help from the government with the drug-residue and quality-assurance system the most because the guarantee of public confidence is very important to us.'

His company will focus on feeding profitable species.

'We used to feed three kinds of fish but now we'll focus on garoupa because it's more lucrative,' he said.