April 28, 2008

 

Fish kill threatens Philippines' Taal Lake

 

 

The Bureau of Fisheries and Aquatic Resources have warned that fish kill can happen in Taal Lake -- one of the country's major aquaculture sources -- due to erratic weather and massive fishing malpractices.

 

Lea Villanueva, aqua­culture centre chief of the BFAR Inland Fisheries Research Station in Taal, Batangas together with aquaculturist Maurita Rosana, conclude that a fish kill could occur in at least three Batangas towns - Laurel, Talisay and Agoncillo.

 

Rosana said they are already unable to sleep as cloudy weather depletes oxygen, thus, no photosynthesis occurs. Three to four days of heavy rains will result to a fishkill, she says.

 

Fish kills usually take place during the rainy season when the level of hydrogen sulfide in the waters of Agoncillo, Laurel and Talisay is high, resulting in toxic gas emissions that, in turn, deplete Taal Lake's oxygen supply.

 

According to researchers, the presence of heavy loads of organic sediment and increased levels of ammonia, hydrogen sulfide and nitrite in the lake contribute to a fish kill.

 

Improper aquaculture practices are also blamed for the deaths of fish.

 

BFAR advised fish cage operators to harvest their fish before the rainy season when fish kills are likely to happen.

 

Rosana said, adding that when the reading of the dissolved oxygen level reaches 4, farmers are advanced to do an "emergency harvest".

 

Rosana said as parasites, bacteria, algal bloom or die-off, sulphur are other contributors to the fish kill.

 

Rosana also said the large organic load in Taal Lake due to excessive feed and fish wastes from tilapia cages should also be blamed.

 

She said off-flavour or muddy taste is a clear sign of an impending fish kill although off-flavour happens regularly in fish cages and rarely in open water.

 

However, off-flavour has affected open water fish such as tawilis (freshwater sardinella) and maliputo (trevally or Caranx ignobilis) since last February, she said.

 

Prices of tawilis fell sharply to P20 per kilo from P120 per kilo, states Rosana.

 

High levels of nitrogen and phosphorous in fish cage areas in Barangays Sampaloc in Talisay, Leviste in Laurel, and Manalao in Agoncillo cause the off-flavor, she said.

 

Likewise, fish caught from open water areas in Cuenca and Tanauan towns also has had off-flavor since March, Rosana said.

 

Over-construction of fish cages in the Pansipit River in San Nicolas town hampers the water in Taal Lake from flowing into Balayan Bay, thus causing the rapid growth of algae and planktons in the lake, stresses Rosana.

 

As of July 2000, there had been 10,000 fish cages in the lake, according to a survey of the tilapia cage industry conducted by Simeona Aypa for the European Union-funded FISHTRAT Project and coordinated by the Philippine Council for Aquatic and Marine Research and Development.

 

Each cage, measuring 10 x 10 x 5 meters on the average, is stocked with tilapia fingerlings at 50-100 per cubic metre. The fingerlings are heavily fed with six different types of commercial feeds.

 

In order for fish cage operators to observe proper culture management and environmental protection, Rosana recommended the strict implementation of fishery laws by the towns concerned as well as training.

 

Villanueva said the BFAR and local governments saw the urgency in enforcing the lake's unified rules and regulations as a solution to the annual fish kills.

 

An ordinance, approved by the Protected Areas Management Board (PAMB) on March 21, 2007, provides designated fish cage zones and sanctuary areas; limits the number of cages from 10,000 to 6,000; and enforces other rules on proper aquaculture management.

 

Villanueva said the ordinance has been pending for over a year now and the PAMB is still waiting for the approval of Environment and Natural Resources Secretary Lito Atienza so it could be enacted into law. Once the number of cages is regulated, Villanueva says fish kills would be prevented and water can move freely in the lake.

 

Taal Lake, which has a surface area of 24,356 square meters, is the country's third largest, next to Laguna de Bay and Lake Lanao. It was declared a protected area in 1996.