BFAR says fish kill in Lake Mainit due to low dissolved oxygen

Roel Catoto

KITCHARAO, Agusan del Norte – The incidents of fish kill in Lake Mainit have been traced to low dissolved oxygen in the country’s fourth largest lake, initial findings of the Bureau of Fisheries and Aquatic Resources-(BFAR) Caraga said.

Tilapia and carp have been found floating dead in Lake Mainit since a month ago.

The fish kill has affected the livelihood of hundreds of fisherfolk who depend on the lake for their livelihood.

Fisherfolk in towns of Mainit and Alegria in Surigao del Norte including Kitcharao and Jabongga in Agusan del Norte had earlier said they suspect mining activities upstream are to blame for the fish kill.

Dr. Anne Melisa Talavera, officer-in-charge of BFAR’s Regional Fish Health Laboratory of BFAR, said parts of the lake have low dissolved oxygen, at two parts per million (ppm), from the normal level of at least four ppm.

She said bigger tilapia need more dissolved oxygen to survive.

“That’s exactly one of the reasons why bigger ones are affected by the fish kill in Lake Mainit,” she said

BFAR also took samples of water and samples of dead fish for laboratory examinations in Manila.

Nerio Casil,  Director of BFAR-Caraga said that last Thursday that they also tested the water for presence of heavy metals. “Water and fish are also checked for bacterial analysis,” he said.

Darwin Brain Lawas, a marine biologist of Green Mindanao Association said fish growth usually requires 5 to 6 ppm of dissolved oxygen. “Dissolved oxygen levels below 3 ppm are stressful to most aquatic organisms. Levels below 2 ppm will not support fish at all,” he said. There are lots of causes why dissolved oxygen gets low in a body of water. He cited  sudden change of water temperature, purity level, algal bloom, soil erosion and siltation. (roel catoto )