MALOLOS CITY, Bulacan; CAO-AYAN, Ilocos Sur, Philippines – Fish kill incidents widened this weekend with reports of dead fish floating in some parts of Angat Dam in Bulacan and Mestizo River in Ilocos Sur, authorities said Saturday.

The Sagip Sierra Madre Environment Society Inc. (SSMSI) reported that dozens of dead freshwater fish surfaced in some parts of the giant reservoir of Angat.

SSMI officials said their group began monitoring the fish kill parts of Angat Dam in Sitio Maputi, Barangay Kabayunan, Doña Remedios Trinidad.

Dumagat tribesmen living near the area were the first to report a variety of freshwater fish like “tilapia”, “kanduli,” “dalag” (mudfish) and “hito”(catfish) turning up dead.

Bro. Martin Franscisco of SSMSI quoted experts as saying that this might have been caused by a lack in oxygen and rise in ammonia levels in the water.

Francisco explained that this happens when rotten logs and other organic materials such as falling leaves, fruits, twigs and branches crowd the river.

SSMSI personnel have already been deployed to remove rotting logs, driftwoods and other organic materials from the river.

Meanwhile, a large volume of milkfish began to surface along the Mestizo River in Barangays Callaguip and Don Lorenzo, in Caoayan, Ilocos Sur.

“We are still in the process of consolidating the total value of killed fish species in the fish kill incident,” said Caoayan Mayor Germelina Singson Goulart, as she clarified that only 13 fish cages have been affected so far.

Local agriculturist Marilou Factor said either an abrupt change in climate or an overcrowding of fish might have caused the incident.

“These two factors had caused the suffocation of fishes along the river leading to their death,” Factor said.

“Although the effect of fish kill in our river was not severe, I advised our fish cage owners to limit the fish content of their fish cages floating along the water in Mestizo River,” she added.