Extreme cold temperature triggers sulfur upwelling; fish kill looms in Taal Lake

By Saul E. Pa-a

TAAL, Batangas, Jan. 22 (PNA) — The Inland Fisheries Research Station (IFRS) and Protected Area and Management Bureau (PAMB) based in the Taal Lake here reported on Wednesday that the fish kill phenomenon has spread to some 29 fish cages in the Lumang Lipa fish cage zone in Mataas Na Kahoy town around the volcanic lake.

In an interview with the PNA, the Bureau of Fisheries and Aquatic Resources (BFAR)-IFRS officer-in-charge Nenita Kawit said they continue to monitor the natural phenomenon through scientific water sampling and quality-testing two times a day in the Taal Lake fish cage zones and shorelines.

Kawit said their IFRS station detected the natural phenomenon on the increase in the hydrogen sulfide in the lake waters which smell like sulfur or rotten egg and the water discoloration to aqua-marine or blue green.

The IFRS official said this natural occurrence is attributed to extreme cold temperature fanned by the northeasterly wind “Amihan” during the period November until February each year.

She said the depletion of dissolved oxygen in the water due to the cold temperature based on their laboratory tests has dipped to .50 to .77 milligram per liter (mg/l) way below the normal level at 6 mg/l and above.

She assured the IFRS monitoring station here constantly coordinates with the fish cage operators and fishermen association in the Taal Lake coastal communities for updates on the fish mortality.

The Taal Lake waters also experienced water discoloration on January 29 to February 4 last year according to the Department of Environment and Natural Resources (DENR)-PAMB.

PAMB officials said the inland fishing communities expected this yearly occurrence on water discoloration in the Taal Lake environment since it was initially detected in 2004.

BFAR Calabarzon also last detected the fish kill phenomenon in May last year which affected the lake’s coastal towns of Agoncillo, Laurel and San Nicolas, Batangas.

Victor Mercado, DENR-PAMB protected area superintendent estimated the damage of the fish kill in the 29 fish cages at some P2.17 million which covered some 14 fish cages for bangus (milkfish) and 15 cages for tilapia.

Mercado said the natural phenomenon on the sulfur upwelling or an increase in the hydrogen sulfide content in the Taal Lake spread to neighboring fish cage zones from the Tanauan City’s no fish cage areas.

As of Tuesday, some 120 tons of fish worth P10.5 million were already affected by the fish mortality due to low temperature in the lake environment since January 19.

The PAMB official said the sulfur upwelling with cold temperature triggered the fish mortality in the fishing grounds of Barangays Aya, Quiling, Tumaway and Sampaloc in Talisay.

He said the lake’s overturn from sulfur upwelling and extreme cold temperature increased water density with heavy sediments settled below the water surface.

Of the 2,000 fish cages in Talisay, Batangas, the 56 fish cages initially affected was placed at P10.5 million pesos damage to the inland fishing industry here.

He noted however, the income loss so far represents a small percentage from the multi-billion fisheries and aquatic business ventures through the 6,000 fish cage harvests here that could fetch annual income of P4 billion.

He assured the Task Force Taal Lake intensifies monitoring on the situation in coordination with the multi-agency agencies DENR-PAMB, Dept. of Agriculture (DA)-BFAR, local government units of the lake’s coastal towns and the Taal Lake Aquaculture Alliance Inc., an association of fish cage operators and fisherfolks.

Mercado also said the Task Force has already activated the quick response team (QRT) composed of national and local government agencies.

The Task Force QRT continues to monitor and assess the extent of damage in the affected areas; obtain information and the subsequent dissemination; ensure proper disposal of the dead fishes and assure these fishes are buried in the pre-identified mortality pits.

Fish cage operators and fishermen were also advised to conduct emergency harvesting of their fish stocks with the harvestable sizes and move their fish cages in the unaffected areas.

Mercado also said aerators and water pumps are installed to infuse more oxygen content in the lake waters.

According to Mercado, the Taal Lake fishermen and fish cage operators discovered as early as January 16 that the fish no longer eat the feeds. (PNA)