Over 100 metric tons of tilapia, bangus lost to fish kill in Taal Lake; did volcano unrest cause it?

More than 100 metric tons of tilapia and milkfish or "bangus" were lost to fish kill that hit Taal Lake in Batangas, the Bureau of Fisheries and Aquatic Resources (BFAR) bared Tuesday, July 6.

Fish pens in Agoncillo, Batangas photograped on July 3, 2021 amid Taal Volcano's continued unrest. (Mark Balmores/ MANILA BULLETIN)

BFAR-4A Regional Director Sammy A. Malvas said an estimated volume of 109 metric tons of bangus and tilapia valued at P8.999 million were affected by the fish mortality incident in Talisay, Batangas.

However, Malvas was quick to rule out Taal Volcano's restiveness as reason for the die-off.

"Walang direct na kaugnayan yung sulfur na binubuga ng bulkan. Walang koneksyon doon sa pagbaba ng dissolved oxygen (There is no direct link between the sulfur emission of Taal Volcano to the lowering of dissolved oxygen in the lake)," the regional director said.

Based on the water quality assessment report on Taal Lake on Monday, July 5, the dissolved oxygen (DO) in several areas such as Tanauan and Talisay registered at 2.38–3.80 milligrams per liter (mg/L), which is significantly lower than the standard level of 5.0 mg/L for dissolved oxygen.

Furthermore, the levels of ammonia (0.12–0.21 mg/L) and sulfide (0.01–0.10 mg/L) were also "above the standard level which are potentially harmful to fishes."

According to Malvas, the only possible effect of Taal Volcano's unrest to the lake is turning its waters acidic. But the water quality analysis results show this is not the case.

"Hindi po acidic yung tubig sa lawa as of yesterday. Nasa alkaline pa o basic. Hindi po siya acidic so wala pong direct na link yung binubugang sulfur ng bulkan doon sa pagbaba ng dissolved oxygen (As of yesterday, the water in Taal Lake wasn't acidic. It remains alkaline or basic level. The water is not acidic so there is no direct link between the sulfur from the volcano and the low level of dissolve oxygen)," the official explained.

He also noted that the volume of fish loss due to the incident "is only a small portion of the total harvest in Taal Lake."

The public were also reminded that the fishes affected by the incident were no longer safe to eat.