The Bureau of Fisheries and Aquatic Resources (BFAR) on Monday said high levels of chemicals caused the fish kill in five villages in Rosario, Cavite.
Based on initial findings, the Quick Response Team and the Fish Health Unit personnel of BFAR-4A said water samples collected at the villages of Bagbag Uno (B), Ligtong 3 and Ligtong 4 indicated a dissolved oxygen (DO) level below 3-5 mg/L or within the critical level.
“The water quality test came back with high levels of ammonia-nitrogen, nitrite-nitrogen and phosphates, beyond acceptable level, in all the sampling sites,” BFAR said in the report.
Ammonia is a chemical compound produced naturally from decomposing organic matter, including plants, animals and animal wastes. The ammonia in the water samples, however, might have also come from agricultural, domestic and industrial wastes.
Phosphates, on the other hand, are one of the primary nutrient sources for many forms of algae and could come from sources like domestic sewage and runoff from agricultural land, urban areas and green areas (PEMSEA and MBEMP TWA-RRA in 2006).
The BFAR said the chemicals at alarming level have hazardous effects on fish, which may result in fish mortality. The agency is closely working with the local government of Rosario in monitoring the water quality of the river and has recommended the necessary management measures during the fish mortality occurrence such as proper disposal of dead fish.
“This is to ensure that dead fishes will not reach the market and prevent sanitary-related diseases from happening,” the BFAR report said.
On September 24, residents near Malimango River noticed that the fish were surfacing the water and “gasping for air.” Later on, they saw dead fish floating on the river, particularly, in area where it flows into Manila Bay.
The four-kilometer Malimango River starts from Bagbag 1 and ends in Ligtong 1 where it opens to Manila Bay. The river traverses the villages of Bagbag 1, Bagbag 2, Ligtong 1, Ligtong 3 and, Ligtong 4.
The stretch of Malimango river is not an aquaculture-producing area and the fish affected by the mortality were wild stock species of ilapia,asohos (silago), banak (mullet) and biya (goby). The loss is estimated at one metric ton.
The Fish Health Unit personnel of BFAR-4A in collaboration with the Municipal Environment and Natural Resources Officer of Rosario collected water samples and conducted dissolved oxygen readings in Tramo, Bagbag Uno (A); Tramo, Bagbag Uno (B); Marcella St., Ligtong 3; Ligtong 4; and Ligtong Uno (river mouth).