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A sudden drop in temperature leading to oxygen depletion may have caused the death of 800 tonnes of fish in a lake south of Manila. The fish began to rot last week.
The fish are being buried in Talisay and three other towns in Batangas province. Selling the fish has been prohibited, said Rose del Mundo of the Bureau of Fisheries and Aquatic Resources (BFAR).
The fish mortalities are said to be unrelated to recent signs of activity in the small Taal volcano near the lake, where many villagers have farmed milkfish and tilapia.
On Monday, government volcanologist Allan Loza said magma might be emerging within the volcano, as 115 earthquakes were felt in Taal in the previous 24 hours, compared to an average of 10-15 daily earthquakes in recent weeks.
An initial investigation showed the mortalities might have been due to the shift in temperature. The rainy season began last week following very high temperatures and caused a sudden drop in water temperatures, which exhausted the lake's oxygen levels, according to Talisay agricultural officer Zenaida Macatangay.
The Department of Environment and Natural Resources (DENR) is warning aquaculture farmers to refrain from feeding their fish excessively, as this can help trigger fish deaths. Chronic fish deaths of this kind in Taal Lake and elsewhere signal the need for better aquaculture practices, DENR said, as excess fish feeds sink to the bottom, rotting and polluting the water and depleting it of dissolved oxygen (DO), which the fish needs to survive.
“Drastic reduction of DO, which is the oxygen in water, will cause fish kills,” DENR Secretary Ramon Paje said.
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