Reader weighs in on Taal Lake woes

EDMUNDO Enderez stumbled upon the PCIJ’s recent report on the sorry state of Taal Lake while browsing the Internet. A concerned citizen, no less a fisheries graduate who previously worked with two government agencies and a nongovernmental organization, he said he was prompted to write the PCIJ to share with our readers his ideas and what he knows about the issue.

Below is what Enderez wrote:

In the early 1970s, the Association of Southeast Asian Nations (ASEAN) established the Aquaculture Department of the Southeast Asian Fisheries Development Center (SEAFDEC) in the country to focus on aquaculture research and development. The center also set up a capture fisheries station in Thailand and a fish processing station in Malaysia.

It was SEAFDEC that developed the aquaculture technology for Laguna de Bay. The technical feasibility and financial viability of aquaculture led to the establishment of fish pen and cage projects in Laguna de Bay and Taal Lake.

Based on scientific studies, SEAFDEC and other fisheries experts put a limit on the area to be used for aquaculture — 10,000 to 15,000 hectares for Laguna Lake and 6,000 units of fish cages for Taal Lake. Due to political intervention, however, the scientific basis for such limits has been largely disregarded, leading to overcrowding of fish pens and fish cages. Such that in Laguna de Bay, the area of 5,000 hectares in 1973 expanded to 31,000 hectares in 1982. Meanwhile, the ideal number of 6,000 units in Taal Lake has already been breached with the presence of 9,000 to 10,000 fish pens and cages.

The situation is aggravated by the inadequate transfer of aquaculture technologies from the technicians of the Bureau of Fisheries and Aquatic Resources (BFAR), SEAFDEC, and feed distributors to the caretakers and local technicians.

The occurrence of fish kills is one of the major negative results of these two factors.

There are several factors to be considered in aquaculture or fish culture in Taal Lake:

1. Water exchange or water current does not occur in Taal Lake, unlike in the sea where there is tidal fluctuation of up to two meters every 12 to 24 hours that causes water current or the movement of large water columns.

2. Dissolved oxygen (DO) at not less than 5 ppm (parts per million) and ammonia level (not sure of minimum level) are important parameters that need to be monitored. Their levels are affected by the number and biomass of fish and quantity of feeds, as well as the water exchange. Without using oxygen and ammonia meter to determine their levels, an experienced technician can observe and sense if these two parameters are making negative effects through the a) movement of the fish, b) feeding behavior, and c) formation of sludge or film of dirt at the water surface, among others.

3. As shown in the map above, the Taal Volcano land mass serves as a wall or protection against the winds. Thus, during the southwest monsoon (habagat) which occur from May to October, the water area of the towns of Laurel, Agoncillo, and San Nicolas is relatively calm, with little wave actions that are supposed to create oxygenation of the water particularly at night time. On the other hand, during the northeast monsoon (amihan) occurring from November to April, the water area of Talisay is relatively calm, with less oxygenation of the water. This explains the fish kills in Laurel and Agoncillo that occurred in August to September of 2007, as well as in Talisay in December 2006. The fish kills were due to very low dissolved oxygen levels and high concentration of ammonia (and nitrite) and hydrogen sulfide.

4. During the fish kill episodes, how low the dissolved oxygen and how high the level of ammonia were depended on the quantity of fish and amount of feeds being given, on the one hand, and the water exchange, on the other. The number of cages in the lake increased to 5,143 units in 1998 and then to 7,433 units in 2001. It then went down to 6,866 units in 2006, after which it went up to 9,000 or 10,000 units.

Possibly due to the occurrence of fish kills in the past, the ideal number has been pegged by the authorities at 6,000 units (10 m x 10 m x 6 m) with the stocking density of 50 fries per cubic meter. In 2006, the total number of cages was 6,688 units with a harvest of 48,896 metric tons, although fish kills occurred in Talisay in December 2006. Given these figures, the expected harvest is 45,000 metric tons at 4 to 5 pieces per kilo (mortality considered).

5. With or without fish kill occurrences, the harvested tilapia has bad flavor. Research has shown that the flavor attributes of cultured fish is related to environmental influences rather than to specific nutrients from the feeds given to the fish. This is true for cultured species since, for obvious reasons, fishes are cultured in near-static water conditions or in areas where there is not much oxygenation of the water. In this type of environment, the growth of flavor-producing organisms, decomposing plant growth, and unconsumed feed all contribute to the organoleptic characteristic of the fish.

6. In 1998 when fish cages numbered 5,143 units, the capture fisheries landings (quantities of fish caught and brought to land) from the lake were only 1,681 metric tons, representing a quarter of total landings in 1992. This could be due to the proliferation of the fish cages and overfishing. Likewise, the occurrence of high levels of sulfur in the water had been blamed to the low fish catch from the wild.