By Ellalyn De Vera, 29th September 2014;
Low dissolved oxygen level and toxic pollutants have caused the fish kills in Rosario, Cavite last week, according to the Bureau of Fisheries and Aquatic Resources (BFAR).
The BFAR Quick Response Team and the Fish Health Unit personnel of BFAR-Region IV-A were deployed in Rosario, Cavite last September 25 following a reported incident of fish mortality in Malimango River, a four-kilometer river, which starts in Barangay Bagbag 1 and ends in Barangay Ligtong 1 where it opens to Manila Bay.
The river traverses five barangays in Rosario, Cavite namely; 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 Tilapia (Oreochromis sp.), asohos (sand whiting) (Sillago sp.), banak (mullet) (F. Mugilidae) and biya (goby),” BFAR reported.
The loss is estimated at one ton.
“Initial findings indicated that dissolved oxygen (DO) level in all three sampling points—Barangay Bagbag Uno (B), Barangay Ligtong 3 and Barangay Ligtong 4—was below 3-5 mg/L or within the critical level,” it said.
“The water quality test came back with high levels of ammonia-nitrogen, nitrite-nitrogen, and phosphates, beyond acceptable level, in all the sampling sites,” it added.
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, meanwhile, 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.
These chemicals at alarming level have hazardous effects on fish which may result in fish mortality, BFAR added.
BFAR has recommended the necessary management measures during the fish mortality occurrence such as proper disposal of dead fish to ensure that dead fish will not reach the market and prevent the occurrence of sanitary-related diseases.
Source: Manila Bulletin