Buhi Fish Kill Caused by Highly Polluted Waters --BFAR

Legazpi City (12 November) -- The massive fish kill that hit Lake Buhi on October 29, 2010 was caused by highly polluted waters according to the water quality monitoring conducted by the Bureau of Fisheries and Aquatic Resources (BFAR) Regional Office No. 5.

Water quality survey was conducted with the physical and chemical parameters tests such as water temperature, dissolved oxygen, pH, ammonia nitrogen, nitrite nitrogen and hydrogen sulfide. The first sampling was done in five stations on November 2, 2010 while the second test was conducted in eleven stations two days later.

Based on the results obtained, Lake Buhi has very low dissolved oxygen content and very high ammonia nitrogen concentration as compared to the optimum ranges set by the South East Asian Fisheries Development Center (SEAFDEC). Moreover, very high traces of hydrogen sulfide was detected in five sampling stations during the water quality monitoring conducted on November 4. This critical water condition of the lake probably led to the massive fish kill in Lake Buhi.

Low dissolved oxygen (or low volumes of oxygen in the water) occurs when water temperature rise and stratification occurs during respiration of plants and fish and during aerobic decomposition of organic matter. Under low dissolved oxygen, fishes will have poor growth, be prone to diseases or even die.

It was also observed that about one-fourth of the lake is covered by water hyacinth which contributed to the depletion of dissolved oxygen by blocking the sources of oxygen such as photosynthetic activity by phytoplankton and wind aeration.

Meanwhile, ammonia (NH3) is the major end product of protein catabolism excreted by fish. Its unionized form called UIA is highly toxic. It is caused by decomposed organic matters like unconsumed feeds and fertilizers, industrial and domestic wastes and decomposition of phytoplankton.

Hydrogen sulfide (H2S) is a poisonous gas which arises from a by-product of decaying and decomposed organic matters like unconsumed feeds, plant debris, dead phytoplankton and fish feces. Too much of this will cause mass mortality due to suffocation and hemorrhages in gills of fish.

These results were presented by Irmi Mora, BFAR Regional Fish Health Officer to municipal officials of Buhi on November 6, 2010 during a meeting held at the town's session hall. Also present in this activity was a team from the Environment Disaster Management and Emergency Response Office of the Province of Camarines Sur headed by Luzena Bermeo; Caridad Roxas, Fishery Division Chief of the Provincial Agriculture Office and Central Bicol State University for Agriculture Environment Science Professor Joyce de la Trinidad.