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Buhi Fish Kill Caused by Highly Polluted Waters –BFAR

source: RA Canabe |

Lake Buhi in Camarines, Philippines

Lake Buhi in Camarines, Philippines

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.

The 2007 data of the local government of Buhi showed that there were 15,597 registered fish cages that occupy 226 hectares of the 1,707 hectare lake. However, Lake Development Officer Ronilo Leal said that there are more to this figure with the growing number of unregistered fish cages.

Fish cages in the lake produce 9 to 10 tons of tilapia daily. About 100 tons of tilapia and other fish stocks was lost due to the recent fish kill with an economic value of P80 million.

Section 51 of Republic Act 8550 or the Philippine Fisheries Code limits aquaculture activities such as fish cages and fish pens in lakes to only 10% of the lake’s surface area. Ideally, the allowable percentage specified by law for fish cage culture in Lake Buhi should not exceed 170 hectares. However, the registered fish cages in Buhi Lake alone exceeded the allowable percentage.

Municipal Councilor Zaldy Arcilla commented that the implementation of this national law can have more teeth once the municipal fishery ordinance (which is now on its second reading) is approved. He admitted that up to ninety percent of the lake has been occupied by fish cages contrary to the prescribed ten percent. He added though that the other lake resource users such as the National Power Corporation‘s Hydro Electric Plant and the National Irrigation Administration’s controlled structure in Tabao River complicates the problem of increasing siltation of the lake by blocking the lake’s outlet in washing out sediment and water hyacinth.

Municipal Administrator Beethoven Nachor presided over the meeting representing Mayor Rey Lacoste who was on official travel. He proposed a stakeholders conference to be attended by fish cage operators and marginal fisherfolk with BFAR officials and other researchers as resource speakers.

BFAR-Bicol Regional Director Dennis del Socorro for his part said that regular water quality surveys will be done by his office at least once a week and support remedial measures in coordination with the Local Government Unit such as capacity building trainings, provision of alternative livelihood to displaced fisherfolk and fish stock enhancement in Lake Buhi.

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