SAN PEDRO CITY—At least 50 tons of cultured tilapia were lost as fish kill hit parts of Taal Lake in Batangas province, a normal phenomenon that occurs during the cold months, according to experts.
Mario Balazon, spokesperson of Taal Lake Aquaculture Alliance Inc. (TLAAI), said the fish kill occurred on Saturday night off the villages of Aya, Quiling and Tumaway in Talisay town. He said 25 out of the 750 cages there were affected.
The phenomenon was caused by the lake’s “overturn” and a possible sulfur upwelling brought about by the northeast monsoon.
An overturn happens as cool water at the top of the lake becomes heavier and goes down, while warm water rises to the surface, explained Dr. Macrina Zafaralla, a scientist of the University of the Philippines Los Baños. This process causes sulfur and other organic matter on the lake bottom to rise and affect the fish in the cages, she said.
“But that’s not all,” Zafaralla said, citing other factors for the fish kill, such as the lake’s bottom topography, wind direction and oxygen level. The phenomenon is observed during the cold months, or from December to February.
The Inquirer on Monday tried to contact the Bureau of Fisheries and Aquatic Resources in Calabarzon (Cavite, Laguna, Batangas, Rizal, Quezon) but was told the director and all division chiefs were still in a meeting to discuss the fish kill.
Mostly affected were the fish in the cages, Balazon said in a phone interview on Monday. “The wild [fish] can swim away to the unaffected parts of the lake,” he said.
TLAAI, a group of fish cage operators, is working with Zafaralla, who has been conducting a study since 2012 on the lake phenomenon, so early warning measures can be drawn up.
His group was still monitoring other lake areas in Lipa City and Mataas na Kahoy town, as it warned other fish cage owners that the phenomenon is expected to reoccur anytime until the end of the cold season.
Balazon said the dead fishes were buried in compost pits on Sunday.
The number of affected fish cages this year was more than that last year, although it was still “relatively small,” considering that Taal Lake has a total of 6,000 fish cages, he said.
Some cage operators were able to harvest before the fish kill, he added.