BFAR warns of fishkill as water quality in Taal Lake declines

FISHING GROUND Taal Lake, a major tourist attraction in Southern Tagalog, sustains the aquaculture industry in Batangas province. Tilapia grown in fish cages in the lake are supplied in markets in Calabarzon region and Metro Manila. —REM ZAMORA

SAN PEDRO CITY, Laguna, Philippines — The Bureau of Fisheries and Aquatic Resources (BFAR) on Wednesday advised fish cage operators in Batangas province to keep watch, and, if possible, begin harvesting their stocks amid the poor water quality in Taal Lake.

The warning of a possible fishkill came after the results of BFAR’s Sept. 10 water monitoring noted “high concentrations” of sulfide and ammonia in the water in sampling sites in three lakeside towns, putting at risk the cultured fish.

Water samples were taken from the lake’s portions in the villages of Bañaga and Manalaw in Agoncillo town, the villages of Leviste and Buso-buso in Laurel town and the villages of Quiling, Sampaloc and San Isidro in Talisay town.

Oxygen drop

According to the BFAR, sulfide was at .01 to .93 milligram per liter (mg/L), exceeding the standard level of .002 mg/L; while ammonia was at .24 to .37 mg/L, above the standard .02 mg/L.

On the other hand, the water’s dissolved oxygen plummeted to 3.10 to 4.81 mg/L, or below the 6 mg/L needed for the fish to survive.

In May, over 600 metric tons of tilapia, the top variety of cultured fish in Taal Lake, were lost to a fishkill.

Marlo Balazon of the Taal Lake Aquaculture Alliance Inc., an association of cage operators, said that such conditions normally occur as weather changes, for instance during the onset of the southwest monsoon.

Cage transfer

Balazon said that tilapia growers had been regularly harvesting stocks once the fish reaches its “marketable size.”

“But you cannot do an early harvest massively because there’s not enough market. If you harvest, say 100 tons, the excess [fish] will just end up rotting away,” he said in a telephone interview.

Balazon said that operators began moving away fish cages to parts of the lake that seemed to be safe from a possible fishkill.

The BFAR also advised fish growers to take measures, like using oxygen tanks and pumps, to supplement the oxygen requirement of the their fish stock. —Maricar Cinco