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FEED Business Worldwide - August, 2011
Philippine fish kills & environmentally unfriendly fish farming  
by Gemma C. DELMO in Manila
In the Philippines, fish kills are not a rare phenomenon. Though devastating, their occurrence happens sporadically and doesn't necessarily come as a surprise to Filipinos.  However, late May's fish die-offs in roused the attention of not only the fishing industry but of the whole country, as they simultaneously occurred in two major aquaculture producing provinces; Batangas and Pangasinan. Aside from hitting the two biggest producing areas at the same time, this die off is the worse in ten years as more than 100,000 tonnes of fish were killed, with losses reaching reach PHP200 million (US$4.64 million).
Authorities say the numbers may still climb as fish fatalities from some towns are yet to be reported.
Observers say the disaster was a lethal combination of climate change and arrant neglectful practices on the part of fish farms.  Whichever way, experts conclude that the industry is about to face its toughest challenge yet.
Man-made or natural?
According to the Philippine Bureau of Fisheries and Aquatic Resources (BFAR), fish kill results from natural or man-made causes.  Factors leading to fish kills include reduced oxygen in the water which may be due to conditions such as drought, algal blooms (caused by phosphate), overpopulation or a sustained increase in water temperature orpollution caused by man. In lakes, a natural phenomenon known as water overturn or upwelling occurs as a result of changes in weather or geologic events--from long dry spells to sudden strong rains or volcanic eruptions, among others.
The country has suffered a string of notable fish kills over the years. In 2002, a fish kill hit Bolinao in province of Pangasinan, destroying about PHP400 million (US$9.35 million) worth of milkfish cultured in fish cages.
In 2007, another occurrence of fish decimation hit the Kakiputan Channel between Bolinao and Anda also in Pangasinan, killing at least PHP100 million (US$2.33 million) worth of milkfish.
In 2009, a series of fish kills occurred in 1,528 hectares of fishponds in Pampanga, Bulacan and Bataan provinces. Last year, severe water pollution caused massive fish deaths in Lake Buhi in the province of Camarines Sur.
The towns of Anda and Bolinao were again the victims of fish kill and along with them, the towns near the Taal Lake in Batangas namely Talisay, Laurel, Agoncillo, San Nicolas, Alitagtag, Cuenca and Santa Teresita. According to fish operators, they were surprised to see fishes floating one morning with nary a hint a day before that a fish kill would occur.  "It was just an ordinary day our fishes were all moving the waters were calm. We were just shocked to see them dead the following day," recounts one fisherman.
The brunt of the fish kill was so severe that fishermen have to sell their fish for as low as PHP2/kg (US$0.05/kg) from the usual PHP60/kg (US$1.39/kg) to PHP90/kg (US$2.09/kg), as people were afraid to buy fish for fear of contamination. 
Some fish operators were grieving at the huge financial loss, mulling if whether they would be able to live another day. "I don't know where I will get our next meal or our allowance for the next day because nobody buys our fishes anymore," tells one fish operator. "Much as I want to feed them with our own fish since I don't have enough money to buy other food, I'm afraid that it's not safe and it might do more harm to my family than good."
Aquaculture mismanagement of water resources
Dubbed as the worst fish kill in recent years, aquaculturists say the disaster was a combination of environmental factors and manmade miscalculation.   Fish-pen overcrowding, an overcrowding-linked sudden drop in water oxygen levels and pollution have all contributed to the fish kill amid warning from scientists in recent years of a possible destruction of our marine ecosystem due to erroneous fish farming structures.
According to BFAR, the fish kill in Taal Lake was due to a lack of dissolved oxygen (DO) caused by the natural upwelling of lake water and colder water from rain storms. The water overturning could also have been induced by the Lake Taal's geology, as an adjacent volcano is showing signs of increasing activity.
In addition to these natural causes, the government identified another culprit at Lake Taal: According to BFAR, what really caused the decimation is the violation of the agency's prescribed Code of Practice for Aquaculture and local government ordinances on proper fish cage management. During its investigations, BFAR discovered that some fish cages had been overstocked and the depths of fish cages were increased from the prescribed five meters to 15 meters.
On the other hand, the fish deaths in the coastal waters of Bolinao and Anda were due to improper fish cage management and overcrowding of fish in the cages. For close water systems such as lakes, BFAR's prescribed stocking density is 20 fish/cubic meter. For open waters, stocking density could go up to 30 fish /cubic meter or more, depending on water circulation efficiency.
However, fish pens were discovered to contain 30 to 50 fishes per cubic meter, making them more vulnerable to weather changes.  It is like putting 20 gold fish in a foot-high box with daily feedings but without changing its water, its aerator been turned off and poured with cold water (the cold water coming from seasonal heavy rains), explains Dr Westly Rosario, chief of the National Integrated Fisheries Technology Development.
Rosario said fish cages in the Kakiputan Channel were stocked beyond the carrying capacity of the water as a square meter of fish cage there contained 50 pieces of milkfish, exceeding the recommended stocking capacity of 25 pieces. The overfeeding then required to maintain such a high fish density then created thick residues of wastes that immensely polluted the water with ammonia and oxygen-destroying compounds. This resulted in a "choking" the fish, tells Dr Edgardo Gomez, professor emeritus from the University of the Philippines Marine Science Institute.
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