SINGAPORE — About 160 tonnes of fish from fish farms on both the East and West Johor Straits have been found dead, possibly due to low levels of dissolved oxygen in the waters or a plankton bloom or both, as well as the hot weather, the Agri-Food and Veterinary Authority (AVA) said yesterday.
The authority has received reports of fish deaths — which include groupers, threadfin, golden trevally and rabbitfish — at 34 fish farms along the East Johor Straits and five fish farms along the West Johor Straits.
TODAY understands that fish supplies to Singapore are unlikely to be affected, as the numbers are relatively low for now. In 2012, fish imports totalled 103,859 tonnes while 5,128 tonnes of fish were produced locally.
Plankton are micro-organisms found in the seawater that can bloom or multiply quickly in a very short time. Plankton blooms can be triggered by fickle weather, higher concentrations of nutrients in sea water and poor water exchange between high and low tides. When their numbers rise quickly, they drain seawater of oxygen and this can result in fish death. The AVA said it has collected samples from the affected farms for analysis and no marine biotoxins were detected.
Clusters of dead fish have been found in various parts of Singapore since last week, including yesterday at the beach at Pasir Ris Park and Raffles Marina. Responding to queries about the dead fish at Raffles Marina, the National Environment Agency said its officers yesterday spotted about 40 dead fishes, most of them mostly grey mullet. “Water samples taken showed that the water quality parameters are in the normal range,” said a spokesperson, noting that the dead fish could have been brought in by the incoming tide.
Last Wednesday, more than 400 dead fish washed up on the shores of the river at Bishan-Ang Mo Kio Park, with the PUB saying they could have died due to the low levels of dissolved oxygen in the water as a result of the recent hot and dry weather.
Fish farmers TODAY spoke to said they last saw such a phenomenon in 2009, and weather changes could have brought it on. Mr Timothy Hromatka, who has been operating FinFisher for the past three years, said: “The change in the local climate (causes) the plankton to bloom which could kill the fish, along with the neap tide.” A neap tide is when the difference between high and low tides is at its lowest, leading to poor water exchange. He estimated that he has lost about 20 tonnes of fish, with losses adding up to about S$150,000.
Mr Phillip Lim, Chairman of Singapore Marine Aquaculture Cooperative, said he has lost about five tonnes of fish worth about S$25,000 to S$30,000, and has taken mitigating steps. “I transfer my fish onto fish nets with green mussels to act as a filter so they can eat the plankton,” he said.
The AVA spokesperson said its staff is assisting and advising farmers to set up standby aeration systems, lower net cages and reduce or stop feeding, so as to improve water quality and circulation to help prevent more mortalities.
A water disposal vessel was activated to collect fish carcasses from the affected fish farms and in nearby fish farming zones and a skid tank will be placed at Changi Point Ferry Terminal, where farmers can dispose of dead fish, the spokesperson added.
Theses photos appear to have been added to the Today Online article when it was updated on 12 Feb at 4.30pm
Channel 8 news report on the mass fish deaths