This has been going on since aquafarming was adopted in place of the normally practiced open water fisheries.
As of 2001, for instance, about 10,000 fish cages had been installed in the lake, it was reported by researchers M.R. Rosana and N.C. Salisi of the Department of Agriculture-Bureau of Fisheries and Aquatic Resources (DA-BFAR)-Region 4.
The study – "Fish Kill Investigation in Taal Lake" – was among those documented by the DA-Bureau of Agricultural Research (BAR).
Rosana and Salisi investigated the phenomenon in Taal Lake and recorded 52 fish kills during the March 1999-June 2001 period. This means an average of two occurrences per month.
"For the past two decades, aquaculture has been practiced with increased stocking density and intensive feeding as the present trend," noted the researchers of BFAR’s Inland Fisheries Research Station.
However, fish kills, which considerably damage the aquaculture industry, are experienced every year.
The direct causes of fish kills are oxygen depletion, toxic poisoning from pollutants such as ammonia and hydrogen sulfide, and attack of Alytropus typus Milne-Edwards (locally known as "timud").
To save Taal Lake, Rosana and Salisi recommended the implementation of consistent fisheries laws, training on aquaculture management, and lake environmental protection for fish cage operators. – Rudy A. Fernandez