January 17, 2008

Philippine fishkill incurs PHP5.6-million losses

Fishkill in the Taal Lake area in the Philippines incurred losses amounting to PHP5.6 million (US$137,000), the Bureau of Fisheries and Aquatic Resources-Inland Fisheries Research Station (BFAR-IFRS) said Tuesday.

Maurita Rosana, BFAR aquaculturist, confirmed that the fishkill affected 31 fish cages in the villages of Aya and Quiling, destroying some 62 tonnes of tilapia and maliputo.

However, Saturday's heavy rains improved the condition of the lake by providing more oxygen to the fish cages, Rosana said. The rain helped flush out waters with pollutants and replace them with clear, fresh water.

Based on a study of Akvaplan-Niva, a group of Norwegian scientists, rain could only flush out up to 10 meters of Taal Lake's average depth of 60 meters.

Decomposing organic substances also remained at the lake bottom, Rosana added.

BFAR said that fishkills have been common in the Taal Lake during the rainy months of November to February due to a natural process called overturn.

Improper aquaculture practices by fish cage operators such as overfeeding and overstocking of tilapia in a cage also contributed to fishkills, according to the bureau.

The agency recommends just 30,000 to 50,000 tilapia fries per cage, yet some operators sometimes stocked up to 400,000 fries per cage to meet their quota.

Although fishkill occurrences in Taal Lake could not be easily prevented, the probability of their occurrence could be reduced, BFAR concludes.