LOS BAÑOS, Laguna – Water conditions in Laguna Lake have returned to normal as of this Tuesday after a fishkill in parts of the lake in the Laguna and Rizal provinces.
“The lake has normalized although we cannot say that [a fishkill] won’t happen again. It’s really hard to predict,” said Neric Acosta, general manager of the Laguna Lake Development Authority (LLDA).
Acosta and Asis Perez, head of the Bureau of Fisheries and Aquatic Resources (BFAR), visited this town to meet with a number of fishermen who lost revenue because of the fishkill.
The officials also took a boat ride to check the lake’s condition in parts of this municipality and in Calamba City in Laguna.
The fishkill that started in the second week of May was first reported in Pakil, Laguna, after 5,500 dead tilapia and kanduli floated in the water and in Jala-jala, Rizal, where 14,000 different types of fish died. Last week, local government officials reported a fishkill in the villages of Masili and Sucol in Calamba City.
A week prior to the fishkill, fishermen also complained of the spread of knife fish, an ornamental but carnivorous species feeding on bangus and tilapia fingerlings.
Following Tuesday’s dialogue, officials advised fishermen to harvest the eggs of the knife fish that normally cling to the fish pen’s bamboo posts, to stop it from multiplying in Laguna Lake.
“The knife fish is edible anyway but still an invasive species that is not naturally part of the ecosystem and should be removed,” Acosta said.
He said the fishkill led to the loss of 10,000 kilograms of fish, mostly tilapia, and an estimated total loss of P2 million to P3 million.
Acosta said fishermen suffered most since the fishkill affected fish cages that were closer to the shorelines.
LLDA and BFAR said they would continue analyzing lake water samples to determine the real cause of the fishkill and would deploy patrol boats to monitor the lake’s conditions in the coming days.
“The rapidly changing weather, from hot to cool, may have caused the level of the dissolved oxygen [in the water] to drop, thus suffocating the fish,” Acosta said.
He said the oxygen level, at the time the fishkill occurred, had fluctuated and dropped to around 3 milligrams per liter. The required level of dissolved oxygen in the lake should be at least 5 mg per liter.
LLDA also said in its report that water acidity “ranging from 5.3-8.60 was within the criteria set.”