Taal fishkills cause P200-M losses yearly

LOS BAÑOS, Laguna — Taal Lake’s tilapia industry loses as much as P200 million a year due to "fishkills" triggered by pollution caused by wastes from tilapia cages.

Fishkills have become regular occurrences in the lake, according to researchers Maurita Rosana and Nenita Salisi of the Bureau of Fisheries and Aquatic Resources (BFAR).

Rosana and Salisi, both assigned at the BFAR station in Tanauan, Batangas, discussed the declining condition of the storied lake and its harmful effect on the tilapia industry during the recent Southern Luzon Zonal Network Review and Planning Workshop at the University of the Philippines Los Baños (UPLB).

The two researchers said they recorded 25 fishkills in a year-long study of nine sites in Taal Lake.

They attributed the fish deaths to oxygen depletion and other toxic water quality conditions such as high levels of ammonia, hydrogen sulfide and nitrite, which are prevalent from March to August.

"Lake overturns brought about by prevailing winds and thermal stratification of the lake’s deep water cause the surfacing of the heavy load of organic sediment from the lake bottom," the researchers explained.

They added that excess feed and fish wastes from tilapia cages that have sprouted in the lakeshore areas of the Batangas towns of Agoncillo, Leviste and Laurel were the main sources of the lake’s organic load.

As of July 2000, fishcages in the lake numbered 10,000, according to a survey of the tilapia industry in Taal Lake done by BFAR’s Simeona Aypa for the European Union-funded "Fishstrat" project.

Each fishcage measures an average 10 by 10 by 5 meters. Fifty to 100 tilapia fingerlings are stocked per cubic meter and heavily fed with six different types of commercial feeds.

Rosana and Salisi urged local officials to strictly implement fisheries laws and train fishcage operators in proper culture management and environmental protection.