Even while Singapore tries to boost the supply of locally farmed fish, the latest mass death incident to hit farmers has highlighted the challenges they face.
It was around Chinese New Year last month when fish farmers off Pasir Ris began to notice something amiss: Their fish were surfacing and gasping. This showed oxygen was lacking in the water.
In a desperate bid to save their stocks, the fishermen harvested what they could, aerated the water and moved high-value fish into mussel nets that would filter plankton and waste from the water.
But it was not enough.
Over the following week, thousands of fish died at 34 fish farms off Pasir Ris and five more farms off Lim Chu Kang. The lethal combination of dry weather and neap tides, when high tides are at their lowest, was pinpointed as the cause of the lack of oxygen in the water.
This was the third such mass deaths in five years.
In 2009, farms in the East Johor Strait were hit by a plankton bloom. Plankton compete with fish for oxygen. And last year, dry and low-oxygen conditions off Lim Chu Kang killed fish there.
The Agri-Food and Veterinary Authority (AVA) began a push in 2011 to make local supplies account for 15 per cent of total fish consumed here. The figure is currently 7 per cent. Farms here must also produce 17 tonnes of fish for every half hectare of farm space to keep their licences. This year, the fish deaths will be taken into account by the AVA, which issues the licences, and farmers will be given help to restock farms and buy equipment.
However, the latest figures show that in 2012, just 46 out of 120 fish farms met the 17-tonne target, and 42 did not. The rest were new or had changed hands recently.
Farmers also say they will continue to face seasonal algae blooms, lack of facilities and high costs.
Natural conditions around Singapore are not exactly conducive to fish farming.
The Causeway restricts water circulation in the Johor Strait, and neap tides reduce current flow. While currents are stronger off Pulau Tekong and around the Southern Islands - the two other areas where farms are allowed - the deeper, faster waters there require a deeper double anchor, making it more expensive, said fish farmer Noven Chew, 37.
National University of Singapore emeritus professor Lam Toong Jin, an aquaculture expert, said intensive feeding, organic runoff from land and high temperatures also contribute to algal blooms and low-oxygen conditions.
The choice of fish adds to the challenges. Species such as the grouper are sensitive to low-oxygen conditions, but high labour and feed costs mean farmers like Ms Chew choose to raise these high-value fish to better compete with fish from overseas. Farmers who raise hardier fish like red snapper, milkfish and grey mullet had better luck in the latest mass deaths.
Other pollution sources could arise in the longer term. In an essay on the rise of the Iskandar Malaysia economic zone, researchers from Nanyang Technological University's S. Rajaratnam School of International Studies noted the potential for increased pollution and oil spills and the impact of land reclamation.
A spokesman said AVA will work with farms that have yet to reach the minimum production target, and that they have two years to do so. AVA has also disbursed the second $10 million tranche of its Food Fund to 40 farmers to help with equipment costs. Most of these farmers run small half-hectare farms.
In the long run, help may come from technology. Two farms here have worked out ways to farm marine fish on land. SIF Agrotechnology Asia's land-based hatchery treats recirculated saltwater, and OnHand Agrarian has harvested pearl grouper, tiger grouper, lobsters, mussels and sea urchins from a pilot farm, cultivating a complete ecosystem in the same tank.
Such tank-based farming may mean higher infrastructure costs, but lets farmers control water quality, said RSIS senior fellow in food security Paul Teng.
For food security's sake, some form of government help will probably be needed to maintain farm production in small, high-cost Singapore, Professor Teng added. "It's just like military security. You don't expect returns, you need to secure your borders."