Plankton bloom hits Pulau Ubin fish farms

Melissa Sim, Straits Times 2 Jan 10;
Dead tiger garoupas at Mr Ong Sing Seng's fish farm off Pulau Ubin yesterday. Half of his fish have died due to the plankton bloom, which drains the sea water of oxygen and deprives fish and other marine animals of it. -- ST PHOTO: CAROLINE CHIA

THE plankton bloom that first hit fish farms off Pasir Ris Beach about 11 days ago has since moved farther out to sea and struck those around Pulau Ubin.

About 50 farms around Pulau Ubin have lost their fish to the bloom. Some farms have lost as much as 60 per cent of their stocks.

The Agri-Food and Veterinary Authority (AVA) has explained that plankton blooms occur when one species of these drifting marine organisms predominates over others and multiplies quickly.

The rapid increase in the number of these organisms drains the sea water of oxygen and deprives fish and other animals of it.

The AVA said the current bloom was triggered by fickle weather, higher concentrations of nutrients in the sea water and poor water exchange between the high and low tides.

Mr Ong Sing Seng, 42, a fish breeder and distributor whose farm is off Pulau Ubin, said he could lose up to $800,000. Half his fish have died.

The fish affected by the plankton bloom include the tiger garoupa, sea bass and red snapper. He said he can do little more than aerate the water if the fish continue to die.

Another farmer, Mr David Sim, 54, said 60 per cent of his fish were dead, and that he was now trying to prevent further loses.

Some of the measures include pumping seawater from greater depths to the surface to aerate the water there, and lowering nets so the fish swim in the more oxygen-rich water lying deeper in the ocean.

Mr Sim said he is moving his expensive fish such as the mouse garoupa - which can fetch up to $105 per kg - to an enclosed tank with controlled salinity and temperature.

He hopes the authorities will give affected fish farmers grants to invest in more such tanks, which cost about $10,000 each. This way, the farmers can be protected against future fluctuations in water conditions.

Mr Lee Van Voon, 43, another fish farmer and breeder, said: 'We need to work together with the Government to find new ways to farm fish instead of relying on open-sea farming.'

The 106 licensed coastal floating fish farms here produced 3,235 tonnes of fish valued at $11.4 million in 2008. They accounted for 4 per cent to 5 per cent of the fish consumed here annually.