The trawling ban, intended to save remaining fish stocks in Hong Kong waters, comes into effect on Tuesday.

Lam Law-ping, who has owned the Tak Hing fish ball shop in Kowloon City for 20 years, said he relied on local trawlers to supply him with enough lizardfish and conger-pike eels to produce about 70 catties (42,000 grams) of hand-made fish balls a day. He also produces a larger amount using machinery.

"It is going to affect us greatly. In the worst case, we might have to close down our business," said Lam, who nonetheless supports the trawler ban because it will make fishing sustainable.

Lam is one of the few fish ball makers who still insist on producing the popular fare locally instead of buying cheaper versions from the mainland.

"We are making a meagre profit now but still we don't want to import mainland fish balls because it is against our conscience. We only sell fish balls that we know what they are made of."

The right mixture of meat from lizardfish and eels produces the best taste and texture, said Lam. Without a local supply, he would consider buying frozen fish or fresh supplies from the mainland. But the former option means the loss of freshness, while the latter will mean higher prices as demand increases.

Equally vulnerable is Tai O village's famous shrimp paste industry. The five remaining shrimp trawlers based at the 300-year-old Lantau village will cease operating under the ban.

Industry insiders say the locally made red-brick-coloured paste has already gone for good. The shrimp fishing season ended in the summer and the stock of paste has sold out. It is made from a particular shrimp species, collected just above the seabed.

But many such pastes - produced elsewhere and branded as Tai O's - are still being sold.

Ng Kwun-yau, a 69-year-old fisherman born in Taishan and raised in Tai O, said: "Many places in Guangdong name their shrimp pastes after Tai O, and some of them are available in the village. But the authentic paste has already disappeared."

Ng said the Tai O shrimp paste tasted better and had finer texture than the mainland product.

The heritage foods have been in a long decline because of never-ending infrastructure projects, Ng said.

"We used to trawl where the airport sits today. Now we have moved to places like the Brothers Islands and Yam O, but these places are now also heavily polluted and the number of shrimps has shrunk drastically."

Dr So Ping-man, assistant director of the Agriculture, Fisheries and Conservation Department, said the ban would have only a minimal, temporary impact on local food production.