June 25, 2010
More than US$1 million lost in Philippine fishkill
Fishkill in the Philippines resulted to an estimated PHP50 million (US$1.07 million) worth of bangus (milkfish) along the narrow portion of the Cacquiputan Channel between the towns of Anda and Bolinao.
Westly Rosario, interim executive director of the National Fisheries Research and Development Institute and center chief of the Bureau of Fisheries and Aquatic Resources in Dagupan City, said that based on their water sampling Wednesday, the dissolved oxygen (DO) was at 1.7 parts per million (ppm) at surface and about two to three ppm only at the middle depth.
Rosario said the normal DO for bangus growth is 5 ppm, he said.
Using high-tech gadgets given by the Norway government for the water sampling, he said the bangus has been dead for several days when they arrived at the area because their stomachs were already bloated and many were decomposing.
The water was already thick and had very foul odour, he added.
Rosario said the long rains after hot days prior to the problem could have lowered water salinity and caused the death of micro algae.
As usual the area is good for micro algal bloom because of rich nutrients influenced by aquaculture activities, he said.
When the micro algae suddenly die of sudden decrease in salinity level, Rosario said the DO could have been pulled down to a level the fish cannot tolerate.
This was also aggravated by no tidal action because of neap tide, Rosario said, hence there was no mechanical aeration of the water.
The town also experienced a massive fishkill in 2001 and about PHP300 million (US$6.46 million) worth of bangus was lost.
Prior to the latest fishkill here which started Sunday (June 20), there was a similar incident in 2008 wherein losses also reached millions of pesos.
Rosario observed that there were more fish cages built in the area. He said when the total weight of stocks is big, there is also huge consumption of oxygen among the fishes.
One fish cage yields from 17 to 20 tonnes of bangus which is about 40,000 pieces and commercial feeds consumption is about 2,000 bags for the growing period of about 120 days, he said.
He advised bangus growers to observe "no new stocking of bangus" for at least a month to enable the waters to recover.
