“That was almost a million dollars in losses,” he said, pointing to a lone grouper frolicking in one of his sea cages. “Only one survived and, surprisingly, it is still alive.”

Like many fish farmers, Lee only received what he termed “minimal compensation” under the government’s emergency relief fund, hardly enough to cover his losses. Since the disaster, he has not dared to release any more fry.

“We would just be pouring good money in after bad,” he said.

If his grievances were simmering then, they are at boiling point now – the Agriculture, Fisheries and Conservation Department is proposing to tighten licence requirements for fish farmers. This, on top of lifting a cap on new licences and the addition of four new culture zones to the existing 26.

Fully utilised, the four new proposed zones – Wong Chuk Kok Hoi, Outer Tap Mun, Mirs Bay and southeast Po Toi island – could yield an additional 5,000 tonnes of fish per year, five times the present level of production.

But drawing most ire is a proposal to require licensed fish farmers to maintain fish cages in at least 70 per cent of an entire licensed mariculture site. For each square metre, they must ensure a density of at least 10kg of fish.

Eating fish sustainably: how Hong Kong is decimating fish stocks

“These new rules will basically mean losing their licences,” said Wong Yung-kan, a former fisheries sector lawmaker and representative. “Fish farmers want to farm too, but with red tides and deteriorating water quality, who can guarantee a good harvest?

“We just want the government to tell us whether it is even still suitable to farm fish in Hong Kong waters and, if it is not, please help us leave. Like the trawl ban, they can compensate us or buy out our farms.”

Wong harbours suspicions that it is all an elaborate government ploy to kill the industry with regulation so it can carry out land reclamation unimpeded.

“All the reclamation works in the past have already lowered overall water quality and the damage is irreversible,” he said.

But fisheries authorities have a different assessment.

“It’s not that we want to take back their licences. We just want to ensure better use of public resources,” said Mickey Lai Kin-ming, assistant director for fisheries at the department, adding that there was no rationale to provide any sort of compensation at this point.

“We think all 26 mariculture sites are still suitable for fish farming.”

Under the new rules, prospective fish farmers would have to provide detailed business plans.

There were about 931 licensed operators in Hong Kong producing about 850 tonnes of live fish last year. But about 70 to 80 per cent do not meet licence requirements.

Lai said many of these culture sites were idle, underused, or being used for – legal and illegal – purposes such as personal residences. Currently, a licence holder must be “actively engaged” in mariculture and fully use the space for cultivation.

It was also an open secret that many operators see speculative profits to be made in these transferable permits.

‘Unprecedented disaster’ for fish farmers: deadly red tide kills 36 tonnes of stock

Far from killing mariculture, the new moves were meant to help expand, modernise and raise standards and sustainability in a greying industry, he said. In 2016, farmed fish accounted for just a fifth of all seafood consumed in the city.

“Wild fisheries are shrinking all around the world and the trend is shifting toward modernised farmed fisheries. We want to attract new blood to the sector and provide the space to develop it,” Lai said.

Dr Jim Chu, an aquaculture expert at the department, said poor water quality was not always the cause of poor fish yields. Most of the time it was poor fish fry.

“Twenty per cent of licensed farmers can still farm normally,” he said. “Admittedly, in the past few years, fry quality for some fish like groupers has declined and many are stricken with viruses.”

Red tides were usually non-toxic – the only harmful ones occurred in 2015 and 1998 – and preventive measures such as pumping oxygen into waters beforehand could secure farms from hypoxia – oxygen deficiency in water.

But fish farmers are still not convinced. Yung Shue O fish farmer Ho Yi said the massive 2015 kill had put him knee-deep in debt at the age of 68.

“We sea people have never asked the government for anything and we owe them nothing,” he said. “Now they are trying to displace us.”

The government will continue to consult stakeholders this month.