Fish biodiversity under siege

In Photo: Fishermen unload at the Binangonan Fish Port their catch of knife fish, an invasive fish species, considered as pest by many fishermen in the Laguna de Bay.

THE board of directors of the Laguna Lake Development Authority (LLDA) approved the 2016-2026 Laguna de Bay Masterplan on December 15, 2015, setting key development directions for the sustainable management of the country’s largest freshwater lake.

The updated master plan sets new development strategies, directions and goals, including a commitment to increase annual fisheries production by 10 percent, while pursuing various projects and activities that will benefit stakeholders in the Laguna de Bay region.

Laguna de Bay remains as one of the biggest aquaculture hub in the country, supplying 70 percent of Metro Manila’s daily fish requirement, particularly bangus (milkfish) and tilapia.

In the 1990s, because of the popularity of aquaculture, the number of fish cage and fish pens in Laguna de Bay grew exponentially, with over 15,000 hectares of the lake area having been dedicated to bangus and tilapia production, exceeding the lake’s carrying capacity.  

Cesar R. Quintos, head of the LLDA’s Policy Planning and Information Management Division, said part of the plan is to increase fisheries production, a commitment made by the LLDA to the Governance Commission for Government-Owned and -Controlled Corporations, to ensure a steady supply and stabilize fish prices in Metro Manila, the country’s capital region and home to 12 million Filipinos. This will require strict implementation of the LLDA’s zoning plan to limit the number of fish cages and fish pens within the lake’s carrying capacity, or approximately 10 percent of the lake’s surface, allowing small fishermen to have more fishing ground to cover during fishing expedition in open waters while maximizing space for aquaculture production.

The proliferation of fish cages and fish pens, the unbridled development and urbanization of areas around the lake, indiscriminate dumping of garbage and disposal of untreated wastewater in rivers that drain to the lake, have been choking the lake for decades.

Nevertheless, Laguna de Bay continues to serve one of its most important economic function—fisheries production. 

Threat from invasive alien species

Lately, however, small fishermen, including those engaged in aquaculture, are fretting about huge production losses as the Laguna de Bay faces another very serious threat: the proliferation of invasive alien species (IAS).

Romy Antazo, a resident of Cardona, Rizal, and secretary-general of the Pambansang Lakas ng Kilusang Mamamalakaya ng Pilipinas (Pamalakaya), a network of organizations of small fishermen, said fish catch in the lake shrunk over the past three years. He blames it on the knife-fish infestation and the failure of concerned government agencies to address the problem.

He said instead of native fish, fishermen like him are catching knife fish, which has low commercial value. Knife fish is sold at P20 a kilo in the market.  Even with its low price, however, consumers tend to buy other known native fish species, which costs an average of P120 a kilo. Also a fish-cage operator, Antazo said bangus and tilapia production is also affected by the knife fish. Knife fish, which grows in fish cages and fish pens, prey on bangus and tilapia.

“Out of 10,000 bangus fingerlings, sometimes we could only harvest 3,000 at the end of the season. This is a big blow to those with limited capital,” he said. Antazo added that said he receives reports about the hardship experienced by small fishermen who depend on the lake’s bounty for several years now.

A number of IAS have been reported to invade the lake in the past, including the janitor fish and Chinese soft-shelled turtle.  The continuing proliferation of the dreaded knife fish in the lake, however, is now considered a major challenge by concerned government agencies as it threatens the lake’s biodiversity and challenges the lake’s economic productivity.

First reported in 2012, the Bureau of Fisheries and Aquatic Resources (BFAR) suspects that knife-fish infestation started with the accidental release by hobbyists in the river that drains to the Laguna de Bay. The fish eventually found its way into the lake, where it now thrives and threaten to render other native fishes extinct.

Because of its feeding habit, the carnivorous fish grows faster than any other fish species in the lake. 

A study conducted on knife fish by the BFAR revealed that for every kilogram (kg) increase in weight or growth of knife fish, it consumes about 7 kg of native fish. Besides smaller fishes, it also feeds on the eggs of other fish species. 

Knife fish reproduces faster and, by sheer number alone, it threatens to render other native fish species in the lake extinct.

The negative effect of the knife fish infestation to the livelihood of small fishermen is enormous.  But more daunting is the thought that some of the better-tasting and commercially viable native fish, such as biya, ayungin, itang and gurami are threatened to be wiped out in the lake.

“We seldom catch native fishes anymore. There are many tilapia and bangus but what we want back are those native fishes,” Antazo said. 

Interagency task force formed

To address the problem, an interagency task force was formed by the government, headed by the LLDA and the BFAR. The task force has launched various programs meant to address the impact of the knife-fish infestation in Laguna de Bay.

Among the measures are the buy-back scheme, wherein the government will pay the fishermen P20 a kilo of knife-fish they catch; cash-for-work program to fishermen and their families who will help manually remove knife fish eggs from the lake to control its population; livelihood programs through value-adding training for communities on how to process food; and massive information campaign about it being “edible” or “safe to eat” to popularize the invasive fish species as food to promote its consumption. 

 While some of the strategies implemented by the interagency task force appeared to have worked well on the janitor fish infestation, it appeared to have failed on the knife fish. 

The LLDA and BFAR are now considering the use of an electrocution gadget to kill the eggs to control the population and, eventually, eliminate the pesky fish from the lake.

LLDA General Manager Nereus O. Acosta said electrocuting the eggs, which has been approved for use in fish pens in a dialogue with various stakeholders conducted by the LLDA and BFAR, is the fastest, safest and most efficient way of getting rid of the knife fish. He said the electrocution gadget will be target-specific and will attack only the fertility of the knife-fish eggs in bamboo poles of fish pens where the eggs stick and widely spread out. “No other eggs or fish will die in the process,” he said.

The gadget designed for the purpose will cover a very small area, enough to electrocute the eggs without harming other fish nearby. For now, he said electrocuting the eggs is seen as the fastest, safest and most efficient way of controlling the knife fish’s population and save other fish species from being extinct.

“There will be no letup in our campaign to eradicate the knife fish. We assure the public that the LLDA and BFAR and other stakeholders in Laguna de Bay are exerting all effort to address the problem,” Acosta said.

IAS are species whose introduction or spread outside their natural habitats threaten or cause the extinction of another species, causing ecosystem imbalance and biodiversity loss.

Threat to biodiversity, food security

The Convention on Biological Diversity (CBD) considers IAS as the main direct driver in biodiversity loss across the globe. It says that alien species that became invasive have been estimated to cost the global economy hundreds of billions of dollars each year.

The threat of IAS in the Philippines is more pronounced in the fisheries sector.

While the introduction of tilapia in the 1970s has boosted the growth of the fisheries sector over the years, other invasive alien species, introduced as a biological agent, such as janitor fish, to help clean waterways, or by way of accident, have become a cause for alarm.

Director Theresa Mundita Lim of the Biodiversity Management Bureau (BMB) said IAS are a serious threat to the country’s biodiversity and food security, as they compete for food and conquer new habitats, displacing other native species to the point of extinction.

She said IAS might occur in any ecosystem, including forests, inland waters, such as lakes and rivers, and agricultural areas.

In some instances, species introduced for food enhancement or as a biological agent to control other pests, such as the golden apple snail, or more commonly called as golden kuhol, caused more harm than good. 

Golden kuhol became a menace when its population became uncontrollable in the 1980s, destroying thousands of hectares of rice paddies.

Policies and processes vs IAS

Lim said national policies and processes on invasive alien species are in place to prevent economic and ecological losses. She said the National Biodiversity Strategy Action Plan (NBSAP) recognizes the threat posed by IAS. On the other hand, Republic Act 9147 provides for the conservation and protection of wildlife resources and their habitats. 

The law prohibits the introduction into the country of exotic species, particularly into Protected Areas and Key Biodiversity Areas (KBAs). She said the BMB has also developed a protocol for the prevention, control and extinction of IAS.

Lim said the BMB is now more cautious in allowing the importation of exotic animals for pets or hobby because of their potential to become invasive species that may disrupt ecosystems, particularly in inland water bodies, a primary source of food and water.

Besides BMB, the BFAR and Bureau of Plant Industry (BPI) have their own set of guidelines to prevent the entry of potential IAS. The BFAR regulates fisheries and other aquaculture species, while BPI prevents the entry of plant species, including fruits, grains and other plant-based products, for agriculture purposes.

Appeal to hobbyists

Lim has appealed to hobbyists to be cautious in releasing their imported pets into the wild because of the possibility that they may become aggressive and dominate other native species in specific ecosystems, such as the knife fish in the Laguna de Bay. 

“Once these invasive alien species start to proliferate, they are very difficult to control because they might have already replaced other species with important functions in the ecosystem. It will require a deeper study before they could be eradicated,” she said.

In his report published in the Philippine Journal of Science, entitled “Impacts of Introduced Freshwater Fishes in the Philippines (1905-2013): A Review and Recommendations,” academician and leading fisheries expert Rafael Guerrero III of the National Academy of Science and Technology (NAST) said based on existing records and observations, 62 freshwater fishes were introduced from 1905 to 2013 in the Philippines for aquaculture (45 percent), ornamental purpose (42 percent), recreational fishing (6 percent), and mosquito control (6 percent).

He said that an evaluation showed that 48 (77 percent) of the fishes are beneficial, 10 (16 percent) are invasive and four (6 percent) are potentially invasive.

Citing various studies, Guerrero identified the six invasive fishes as the “janitor fish” (Pterydoplicthys disjunctivus and P. pardalis), the “jaguar guapote” (Parachromis managuensis), the “clown featherback” (Chitala ornata), the “giant snakehead” (Channa micropeltes) and the “black-chinned tilapia” (Sarotherodon melanotheron).

The jaguar guapote, also called dugong,  a piscivorous fish, compete for food and prey on smaller fishes in the Taal Lake. The clown featherback, locally called arowana, a native of Thailand, has invaded the Laguna de Bay in 2011. Like the knife fish, arowana preys on native fishes, including milkfish and tilapia.

The black-chinned tilapia, a native of Africa, was first observed by Guerrero also in Laguna de Bay in 2008. The giant snakehead, locally known as the black mask, from Thailand also, was reported to be present in the Pantabangan Reservoir in Nueva Ecija.

The BFAR has no record of the introduction of most of these invasive fish species into the country, Guerrero said. This indicates that the introduction of these invasive fish species may have been accidental or done without the knowledge or approval of concerned government agencies. “In terms of economic benefits, the gains derived from the introduction of beneficial fishes, particularly for culture and fisheries enhancement, are much more compared to the economic losses due to the negative impacts of invasive fishes,” Guerrero said.

However, he added that there are very limited studies pertaining to the ecological impacts of introduced freshwater fishes.

Need to improve regulations, processes

Guerrero said there is an urgent need to improve the regulations and processes applied for the importation of live fishes to prevent potential economic and ecological losses. Lim said the fact that species are replaced by another means disruption that may adversely cause ecological imbalance.

The Philippines is ailing from rapid loss in biodiversity mainly because of hunting for food and illegal wildlife trade, and pollution coupled by the massive destruction of forest and coastal ecosystems. Some of the country’s unique and endemic floral and faunal species are now gone, with many others in the brink of extinction.    

Although not an entirely new threat to the country’s biodiversity, invasive fish species are now making their presence felt, threatening the country’s already vulnerable fish biodiversity, invading inland water bodies, including rivers and, now, the Laguna de Bay. 

Image credits: Pamalakaya Public Information Office


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