Demystifying fish kill, shellfish mortality in Manila Bay
By Jonathan L. Mayuga -October 20, 2019
During the celebration of World Food Day on October 16, fishermen belonging to the Pambansang Lakas ng Kilusang Mamamalakaya (Pamalakaya) highlighted the importance of Manila Bay as their primary source of income and livelihood.
The group underscored the need to protect and conserve the historic bay—which stretches from Cavite to Bataan—a traditional fishing ground of small fishermen in Luzon and a major source of food that helps fill the country’s food basket.
No less than the Department of Agriculture-Bureau of Fisheries and Aquatic Resources (DA-BFAR) identified Manila Bay as “a spawning area of sardines” and one of the major fishing grounds of small fishermen.
However, the call to protect Manila Bay against destructive development projects came amid a massive fish kill in Las Piñas and Parañaque, and the shellfish mortality affecting mussel farms in Bacoor and Sangley Point, Cavite, on October 9.
The fish kill and shellfish mortality occurred at a time when the Department of Environment and Natural Resources (DENR) claimed that water quality in some areas have improved significantly, heralding the success of the ongoing rehabilitation efforts to save Manila Bay.
Rich biodiversity
Manila Bay remains to be a rich fishing ground that is able to support the livelihood of small fishermen if protected against illegal fishing methods and other destructive development activities like a massive land reclamation that threatens coastal areas, including Manila, Pasay, Las Piñas, Parañaque and Navotas.
The ocean conservation advocacy nongovernment organization Oceana Philippines recently cited the discovery of a new sardine species, called Sardinella pacifica as a reason to protect Manila Bay and other areas in the country against land reclamation also called dump-and-fill.
However, in a news release on October 14, the DENR said over 200 sacks and over 5,000 kilograms of various marine, species, such as fish, shrimps and crabs were collected from the shores of Las Piñas-Parañaque Wetland Park (LPPWP).
At least 33 marine species, including tilapia, talakitok, sapsap, lapu-lapu, eel, malakapas, crab and shrimp, were among those found dead.
Suspected cause of death
Mystery shrouds the fish kill and shellfish mortality in the areas. The Las Piñas and Parañaque portion of Manila Bay, which is close to LPPWP, is known to be polluted.
Many areas near the shore, particularly along Roxas Boulevard, have a high concentration of fecal coliform even before, yet assorted fish species thrive in these areas.
The LPPWP, formerly known as the Las Piñas-Parañaque Critical Habitat and Ecotourism Area, is a Ramsar Site or wetland of international importance.
According to reports released by the DA-BFAR, the fish kill in Las Piñas and Parañaque could have been caused by poor levels of dissolved oxygen and higher levels of ammonia and phosphates than the standard level.
Laboratory test results
The report was based on water quality test conducted by the DA-BFAR Fishery Law Enforcement-Quick Response Team a day after the fish kill was reported.
For dissolved oxygen, the standard parameter is >5.0 (greater than 5.0) ppm, but the three sampling areas—one in San Dionisio and two in Bay City—showed dissolved oxygen the lower level of 0.70, 2.0, and 0.70, respectively.
For ammonia, the standard level is 0.05 ppm but laboratory tests showed they were way above standard—San Dionisio was 3.59 ppm; Bay City, 1.29 and 1.68, respectively.
For phosphate, the standard parameter is <0.5 (lower than 0.5) ppm, but the laboratory test results were at extremely high levels—San Dionisio was at 6.45 ppm, and 7.11 and 8.28 ppm in the two Bay City sampling sites.
Fatal chemicals
The DA-BFAR Information and Public Relations Group said ammonia is a chemical compound produced naturally from decomposing organic matter, including plants, animals and animal waste.
The ammonia in the water samples, however, might have also come from agricultural, domestic and industrial wastes, the report says.
Phosphate, on the other hand, is one of the primary nutrient sources for many forms of algae, and could come from sources like domestic sewage and runoff from agricultural land, urban areas and green areas.
“These chemicals, at high levels, may cause detrimental effects to the fish which may result in fish kill,” the report said.
Meanwhile, based on the scientific examination conducted by BFAR-4A Regional Fisheries Protection and Law Enforcement Group (BFAR4A-FPLEG), the fish mortality was not caused by blast or dynamite fishing.
Dead ‘tahong’
On October 14, the DA-BFAR said that based on initial laboratory report, the salinity level in the areas, which ranged from 19 ppt to 25 ppt, is lower than the required level for shellfish to survive, which is 27 ppt to 35 ppt.
“The heavy rainfall in the past few days might have triggered the water salinity to drop,” the report revealed. The tests were made by the BFAR4A-FPLEG, the BFAR National Fisheries Laboratory Division, and technical personnel from BFAR-4A in Bacoor and Sangley Point.
The laboratory tests also showed that dissolved oxygen levels in the sampling areas were low, but high concentrations of ammonia and phosphates were detected.
Like in its report on the fish kill in Las Piñas, the DA-BFAR said high levels of ammonia and phosphates may cause detrimental effects to fish and other marine life.
Yet, despite the shellfish mortality affecting mussel farms, consumption of shellfish from the said fishing ground is safe, the DA-BFAR said.
However, it advised that only live shellfish should be collected and washed properly before cooking.
Natural phenomenon
DA-BFAR-4A Regional Director Sammy A. Malvas said their interviews in the affected areas revealed that fishermen are not oblivious to fish kill or shellfish mortality.
“When it is hot and it suddenly rains, mussel dies. This normally happens,” he said.
Supporting the laboratory findings, he said the excessive rainfall in the past few days led to the decrease in the level of salinity, resulting in shellfish mortality.
“Mussel, or shellfish, in general, does not survive in low salinity,” he said.
He believes that for the shellfish mortality, salinity is the main issue, not pollution.
“Mussels are very sensitive to salinity,” Malvas said.
Culprits in fish kill
Meanwhile, the culprits in the fish kill in Las Piñas and Parañaque based on laboratory tests on water samples, were the levels of ammonia and phosphates, as well as low levels of dissolved oxygen.
This means, Malvas said that the water pollution, which could have been triggered by natural occurrence, worsened in these areas.
He said while the water pollution could have been caused by chemicals used in farms like fertilizers, on top of agricultural runoffs, excessive industrial waste discharge and domestic wastes, which include untreated wastewater that causes fecal coliform to spike, were also prime suspects.
However, he said the decomposing organic matters in the waters, including decaying dead plants and animals, and the excess feeds used in aquaculture farms could have aggravated the problem.
Nevertheless, he ruled out the possibility that this could have been caused by the dumping of dead swines in rivers in areas currently affected by the African swine fever.
“It is not possible because the dumping of swines in the rivers were isolated cases and could not possibly result in that level of pollution in Manila Bay,” he explained.
However, because the fish kill and shellfish mortality “was not that massive,” he said the DA-BFAR is not yet considering financial support or subsidy to the affected fishermen.
“What we are doing right now is continuous monitoring the water bodies in the Calabarzon, including the Laguna de Bay,” he said in mixed Filipino and English.
Still unknown source, origin
With the source of chemicals that were believed to have caused the fish kill and shellfish mortality remaining unknown, DENR Undersecretary Benny Antiporda, for solid waste management and the local government units, nixed the possibility of chemical dumping.
However, he said a thorough investigation is being conducted.
Second opinion
Sought for expert opinion, Jimely Flores, a marine and fisheries science practitioner at the Environmental Defense Fund, said the shellfish mortality could not have been caused by low salinity.
“Mussel thrives in less saline areas,” she said.
According to Flores, most mussel farm areas are in bays near big mouths of rivers like Bataan Bay, Manila Bay and other inland seas with river outlets.
She said hence, it is not likely that the shellfish mortality in Bacoor and Sangley point could have been caused by low salinity.
“Salinity in Manila Bay fluctuates a lot and never kill a massive amount of fish and tahong. No, it can’t be the reason,” she said.
“What kills marine organisms is low BOD [biological oxygen demand] but never high BOD,” she said.
For the fish kill, she said the low level of BOD could be one of the reasons but not in the case of mussels.
“Mussels are super resilient,” she said.
But ammonia being the cause of the fish kill may be inconclusive.
“It is important to know how they conducted the test because sampling time is critical. Also, phosphates are not observed to kill marine organisms. Manila Bay is expected to be super high in those [chemicals] already given its polluted state,” she said.
While low BOD could be the possible reason for the fish kill and shellfish mortality, it is interesting to know what is the cause of the low BOD in the waters, she said.
“They [investigators] need to look deeper than mere BOD. Ammonia and phosphates are not conclusive,” she said.
Natural causes of low BOD includes local warming anomaly, plankton bloom, chemical and nutrient pollution, which could also be man-made when dumping happens, she said.
Observing the result of the laboratory test released by the DA-BFAR, she said the 19 ppt to 25 ppt salinity could not kill fish and marine organisms.
“That is still normal,” she said.
While saying that the values on ammonia and phosphates are high, she said it could cause mortality only in fishponds and aquarium where water is stagnant. In the case of Manila Bay, the water current is strong.
“The question should be why is the ammonia and phosphate levels were so high? Marine organisms could die when exposed to high ammonia long enough to reduce their resistance to diseases. It still does not explain the massive death,” she said.
Impact on small fishermen
The twin incidents were sure to affect the livelihood of small fishermen in the affected areas.
Myrna Candinato, president of the Alyansa ng mga Magdaragat sa Bacoor Bay, said small fishermen will likely suffer the consequences.
Every time there is a fish kill or shellfish mortality, consumers are sure to avoid buying fish or mussel from the affected areas.
“Naturally, it means loss of income for us,” she explained.
Worsening water quality?
Candinato said the fish kill and shellfish mortality amid the on-going rehabilitation effort of the government in Manila Bay only proves the water quality has not improved, and even worsened.
She said deadly chemicals that accumulated in the waters of Manila Bay clearly caused the mortality of the fish and mussel in their farm.
“I am afraid that they will again blame coastal communities for the fish kill. As always, we are being blamed for the pollution when in fact these are chemicals dumped by industries,” she said.
Pamalakaya National Chairman Fernando Hicap earlier called for a thorough investigation into the incident.
He said the fish kill and shellfish mortality only proved the Manila Bay rehabilitation effort, instead of improving, caused the water quality to worsen.
Antiporda belied this. He said the DENR is still conducting a thorough investigation and it is too early to jump to such conclusion. He insisted that water quality in Manila Bay has improved as far as reducing fecal coliform levels is concerned.
He said the DENR, which is leading the Manila Bay rehabilitation, has imposed corrective measures among commercial establishments, including hotels and restaurants, earlier found to be illegally discharging untreated wastewater.
The DENR is also requiring these establishments not connected to proper sewer line to put up their own sewage treatment plants to ensure that wastewaters are treated before being disposed to the environment.
According to Antiporda, the campaign to rehabilitate Manila Bay, including rivers that directly flow out to its waters, will be a continuing process.
In the meantime, small fishermen affected by the fish kill and shellfish mortality may have to endure a little longer. And they are asking: What help can they get from the government?
Image Credits: Pamalakaya
