With local produce accounting for less than 10 per cent of their supply, supermarkets still have plenty of fish even after a devastating plankton bloom over the weekend killed more than 300 tonnes of stocks at farms in Changi.
Dairy Farm, which owns both Cold Storage and Giant supermarkets, said neither its supply nor price is affected as it practises "diversified sourcing", buying fresh fish from countries such as Indonesia and Malaysia.
About 10 per cent of Giant's fish supply comes from local farms while Cold Storage buys a "minimal" amount, said a spokesman. Local farms supply species such as grey mullet, golden snapper and golden pomfret, she said.
Home-grown produce makes up just 5 per cent to 10 per cent of FairPrice's fish, and less than 5 per cent of Sheng Siong's.
"Most of the local fish farms do not have the required facilities to transport live fish directly to our chain stores. So, at the moment, most of our live fish comes from Malaysia," said a Sheng Siong spokesman. The supermarket chain buys about 500kg of fresh fish daily from local farmers, mainly milkfish and mullet.
FairPrice and Sheng Siong said they are still buying local fish and reassured consumers that they are safe to eat. Overall, local fish farms contribute about 7 per cent to Singapore's supply.
The unexpected plankton bloom, the second in as many years, affected Changi farms located off Lorong Halus jetty most badly, with some losing almost all of their fish stock overnight. Plankton blooms can be deadly as they suck oxygen from the water, suffocating other marine life.
One farm alone, Marine Life Aquaculture, lost 120 tonnes of threadfin and seabass.
Another, Kelong FC116 in Pasir Ris, appealed for funds on crowdfunding website Indiegogo yesterday to keep operating after losing more than 20 tonnes of fish. It is the second farm to look for help online, following in the footsteps of Ah Hua Kelong.
Between Saturday and last night, Ah Hua Kelong had managed to raise more than $16,000.
Marine life has also been found washed up along the shores of Pasir Ris Beach and near the Sungei Buloh Wetland Reserve Extension.
Dr Diana Chan, course manager for the diploma in veterinary technology at Temasek Polytechnic's School of Applied Science, said the concentration of farms in Changi and their close proximity to each other could create a situation in which water cannot flow freely.
A plankton bloom is caused by various factors like warm temperatures and high nutrients leading to lower levels of dissolved oxygen. It happens worldwide, including in countries such as Malaysia and the Philippines, say experts.
Associate Professor Federico Lauro from the Asian School of the Environment at the Nanyang Technological University said the micro-organisms can double every three to four hours.
"With a better understanding of the many factors leading to a bloom, scientists should be able to provide risk assessment tools for the conditions leading to a bloom. We are just not at that stage yet."
Still, farmers can brace themselves for such eventualities by employing systems to monitor dissolved oxygen and nutrient levels, said Mr Chan Wei Loong, programme chair of Republic Polytechnic's diploma in marine science and aquaculture.
Even though when a plankton bloom occurs is "anyone's guess", a trained person will know how to read this information and be prepared for it, he said.