Photo shows dead milkfish in Dagupan when it suffered from a fishkill in 2011. On Thursday, Oct. 11, 2012, thousands of milkfish went belly up again after a fishkill hit two areas in the coastal city. AP
DAGUPAN CITY, Philippines—Thousands of bangus (milkfish) went belly up here on Thursday after a fishkill hit two areas in this coastal city.
But city agriculturist Emma Molina described the fish kill as “slight” because pond owners immediately harvested their stocks when they observed their bangus gasping for air and swimming near the ponds’ surface.
Molina said at least 15,000 bangus floated in a two-hectare pond owned by Manny Soy in Barangay (village) Tambac while 35,000 bangus surfaced in a three-hectare pond owned by Lucas Ballesteros in Barangay Lomboy.
“In Barangay Tambac, the dissolved oxygen (DO) in the pond was only 0.55 parts per thousand (ppt), while in Lomboy, the DO was 1.55 ppt,” Molina said.
A pond should have at least a DO of 3 ppt for the stock to survive, she said.
This was the first fishkill here after Mayor Benjamin Lim cleared the city’s rivers of fish pens and other fishing structures in 2010.
In May 2002, bangus growers here experienced the worst fishkill when at least P10 million worth of milkfish went belly up in six villages.
Molina said the pond owner in Lomboy overstocked, reducing the DO in his pond. But in Tambac, she said, the DO dropped because of the neap tide (weak tide) and the abnormal weather condition here on Wednesday.
“On Wednesday, it was gloomy in the morning and then the temperature increased toward noon and it was hot in the afternoon. And then this morning (Thursday), it was as if it was going to rain but the sun came out,” Molina said.
She said with the neap tide that began on Wednesday and which will end on Saturday, DO in ponds will continue to be low, increasing the possibility of fishkill if bangus growers will not be watchful.
Molina said a neap tide is characterized by minimal tidal changes that there is almost no water movement, causing low DO level in the water. It occurs when the moon is on its first-quarter and last-quarter phases.
Molina said she sent an advisory to pond owners as early as Tuesday, warning them about the neap tide. She advised them to reduce the stocks in their ponds so fewer fish will share the reduced DO.
“Some listened to us. But others did not,” Molina said.
She said her office has yet to complete the assessment of losses from the fishkill.
During an inspection at the Magsaysay fish market here on Wednesday, Molina said she saw undersized bangus being sold at 10 to 12 pieces a kilogram, leading her to suspect that pond owners were forced to harvest them. The owners may have just opted to save rather than lose them,” she said.
Despite the fishkill, she said bangus price here was “good,” selling for P102 to P115 a kilogram.