ANOTHER fish kill was reported in Taal Lake last Friday as thousands of milkfish and tilapia floated to the lake’s surface in fish cages off Laurel and Agoncillo, Batangas. It had been a hot day followed by heavy rains late in the afternoon.
What may have killed the fish, according to the Bureau of Fisheries and Aquatic Resources was the drop in the lake’s dissolved oxygen from its normal level of 6 parts per million (ppm) on the lake’s surface, down to 0.86 ppm last week. Fish cultured in fish cages need an oxygen level between 5 and 6 ppm in order to survive, the bureau said.
Some fisheries experts say it is also possible that the fish kill was caused by sulfur rising from the depths following the strong rains after the very hot day.
Fish kills could also be caused by diseases from viruses and bacteria, algal blooms, fish toxins from run-off water, and high levels of hydrogen sulfide. A fish kill in the Pampanga River in 2017 was traced to the discharges from an alcohol fermentation plant.
In 2006, the Department of Environment and Natural Resources (DENR) found 14,000 fish cages on Taal Lake, when the ideal carrying capacity of the lake is only 6,000 cages. The number of cages was thus reduced until the authorized level was reached in 2011. With the recent fish kill, the DENR said it may have to further lower the number of authorized fish cages, also considering the increasing number of tourist businesses around the lake.
Government attention is now focused on Taal, with President Duterte himself expressing concern. The President, we may recall, once called attention to the many fish cages he saw in Laguna de Bay from his plane to Davao in the first year of his administration. He acted decisively in the case of Boracay, which he ordered closed for six months of rehabilitation, and has now also ordered the cleanup of Manila Bay.
The DENR is now considering implementing a single-growth cycle for fish cages to give the lake time to rest and recover from the intensive economic activity. Fish kills are a symptom, a sign that something is amiss.
It may be time to give Taal and the many other lakes, rivers, and coastal areas in the country a needed rest from increasingly intense exploitation by business interests.
