An official of the Bureau of Fisheries and Aquatic Resources (BFAR) has warned fish cage operators and residents in lakeshore areas around Taal Lake that a fishkill could occur anew during the cold months from December to February next year.
Leah Villanueva, chief of the Inland Fisheries Research Station of BFAR, said “the water condition in Taal Lake has never been stable up to this time since the massive fishkill in May and early June this year.”
National officials blamed the phenomenon on the abnormal levels of dissolved oxygen (DO) in the lake due to overstocking by fish cage operators and weather change.
Operators suffered millions of pesos in losses following the fishkill that hit seven towns and two cities around the lake in May.
Villanueva said the normal DO level is 6 parts per million (ppm) and above but current levels were alarming based on results of tests in 10 of 11 stations in Talisay, Laurel and Agoncillo towns.
She said the most disturbing results were in Agoncillo town where DO levels were just 4.7 ppm.
Villanueva said BFAR would have tested also the quality of water in San Nicolas town but rough waters prevented BFAR people from getting samples.
She said she feared the rise in levels of hydrogen sulfide and ammonia in waters in the lake.
Maurita Rosana, aquaculturist, said test results in the three areas also showed the two gases were found in the lake.
“The current levels of hydrogen sulfide and ammonia are ‘above normal’ or not normal based on the recent water quality testing,” she said.
Rosana said hydrogen sulfide and ammonia usually come from fertilizers, livestock and poultry manure, and domestic wastes.
She said the normal level of hydrogen sulfide should be less than 0.002 ppm and for ammonia it should be 0.02 ppm.
Rosana said during the cold months “the upwelling of toxic gases would affect both the open water and the water in the fish cages which might result in another fishkill.”
During the fishkill in May to June, Batangas Gov. Vilma Santos-Recto had admitted that “excesses” by fish cage operators were largely to blame.
In a text message to the Inquirer, Ginette Segismundo, spokesperson of Task Force Taal Lake, said “fish pens in Taal Lake are already regulated.”
Earlier reports said that after the massive fishkill, the task force had started dismantling 77 of 1,300 illegal fish cages in the towns of Talisay, Laurel, Agoncillo and San Nicolas.