TANAUAN CITY, Philippines — A fish kill in Taal Lake destroyed at least 18.6 metric tons (MT) of tilapia in the village of Bañaga in Agoncillo town and affected two other villages in Laurel town, the Bureau of Fisheries and Aquatic Resources (BFAR) said Tuesday.
Based on a farm gate price of P70 per kilo, the fish kill had damaged around P1.3 million worth of tilapia in Bañaga alone.
Aquaculturist Maribel Carolino of the Provincial Agriculturist’s Office (PAO), however, said the actual damage to local fishing communities in both towns, including Talisay, could still go up as other affected areas within the lake have yet to be surveyed.
In Tuesday’s partial report issued at 9 a.m., the BFAR-Inland Fisheries Research Station estimated that 34 tilapia cages and five maliputo (Caranx ignobilis) cages, mostly in the harvestable stage, had already been affected by the fish kill in Bañaga.
“Because of oxygen depletion, some fish stocks had started to settle on top of the lake. The fish kills occurred gradually and killed 200-400 kilos of tilapia per cage,” Carolino said in a phone interview.
She added that the local fish cage operators first noticed the dead fishes on Saturday morning.
Carolino said the fish kill destroyed 1.5 metric tons of bangus (milkfish) and two tons tilapia in the village of Leviste, Laurel town while the village of Buso-Buso, also in Laurel, lost 10.5 metric tons of tilapia.
Initial BFAR investigation showed that the level of hydrogen sulfide recorded in all the said villages, were critical and that the toxic gas emissions could have depleted the lake’s oxygen causing the massive fish kill.
Among the sources of hydrogen sulfide were unconsumed tilapia feeds and domestic wastes settling at the lake bottom, said Josephine de la Vega, assistant center chief of the BFAR Inland Fisheries Research Station in Tanauan City.
The BFAR-IFRS is also studying whether the fish died from suffocation due to sulfur upwelling from the bottom of the volcanic lake.
De la Vega said fish kills were common during the rainy months starting in May.
She, however, cited irresponsible aquaculture practices by fish cage operators, such as intensive feeding and overstocking as the primary precursors of fish kills.
“Although the BFAR recommends a stocking density of 50 pieces per cubic meter, the local operators usually stock 375 tilapia fry per cubic meter,” she said.
The agency advised local fish cage operators to gather the harvestable stocks and refrain from feeding the fishes because of decreasing dissolved oxygen content in the lake.
She urged them to practice proper feeding and stocking of tilapia fry in the cages as recommended by the BFAR.
De la Vega appealed to local government units to implement its existing municipal ordinances to regulate the number of fish cages and conduct a regular cleanup of the lake.
Taal Lake , which has a surface area of 24,356 square meters, is the country’s third largest lake next to Laguna and Lanao Lake. It was declared a protected area through the National Integrated Protected Areas System Act by virtue of Presidential Proclamation 906.