There’s the disputed Ayungin Shoal 105 nautical miles west of Palawan, and there’s the endemic freshwater fish called “ayungin,” which is now the size of a fisherman’s palm. But size shouldn’t matter, with both the large reef and the small fry facing the threat of one day being lost to the Philippines.

Ayungin the fish or Leiopotherapon plumbeus, more commonly known as silver perch, breeds and once abounded in the freshwater lakes of Laguna de Bay. Today, it is threatened by high fishing pressure, habitat loss, and increased competition with invasive aquatic species. 

The fish belongs to the group of ray-fins in the family Terapontidae commonly found in the Indo-West Pacific region. It has an elongated oval-shaped body with olive green tint and silvery sheen. Its size ranges from 60 to 88 mm and can reach up to 150 mm when fully mature.

In the 1960s, ayungin was abundant in Laguna de Bay, making up to 70% of the total freshwater fish catch. But its population has sunk to only 1.7%, prodding the International Union for Conservation of Nature and Natural Resources to include it on the red list of threatened species in August 2020.

Now, Filipino scientists and researchers at the Southeast Asian Fisheries Development Center/Aquaculture Department (SEAFDEC/AQD) led by scientist Dr. Frolan Aya are racing against the current to save this vulnerable fish.

“There has been a downward trend in wild ayungin fishery catch since 2002 and this will continue until 2050,” Aya told CoverStory.ph, a calculated prediction he is making after nearly 15 years of ayungin research.

From the rapid downtrend in numbers, ayungin has one of the highest decline rates among freshwater fish in the country. Philippine Statistics Authority (PSA) data show that the annual production of ayungin has dropped by as much as 77% from 4,765 metric tons in 2002 to only 1,114 mt in 2023—a great majority of which were commercially caught for food consumption.

Meanwhile, its value has dropped by 36% in just two decades. From P261,688 in 2002, the total revenue from ayungin production is now tagged at P167,736.

High adaptability

Ayungin was once considered unideal for aquaculture. But years of rigorous research and rearing done by SEAFDEC/AQD and the University of the Philippines in Los Baños and Diliman proved this assumption wrong. Ayungin’s adaptability to spawning and reproduction in capture environments is more than ideal. In fact, emerging hatchery technology may save the species from external threats, and it only takes a little more than 60 days.

Aya and his colleague, marine scientist Dr. Luis Maria B. Garcia, saw the potential of a new hatchery production of ayungin for inland freshwater aquaculture. Their coauthored manual, “Biology and hatchery rearing of the silver therapon Leiopotherapon plumbeus,” is a thorough scientific record of the ayungin, covering its biology, broodstock management, artificial breeding, egg collection, larval and early juvenile development, hatchery rearing, and economic analysis.

Captive breeding, coupled with hormone-induced spawning, is a reliable method in ayungin fish conservation. Based on Aya and Garcia’s study, effective artificial breeding of ayungin uses a cocktail of synthetic spawning agents such as human chorionic gonadotropin and salmon gonadotropin-releasing hormone analogue.

A precise concentration of these hormone-releasing agents is prepared and injected into sexually mature female broodstock, which will later be reared in spawning tanks with the males. Spawning takes about 24 to 33 hours after injection.

In the next 2 to 4 hours, the spawned eggs are collected, incubated in polyethylene tanks, and then allowed to hatch, taking another 24 hours to complete the embryonic cycle.

Newly hatched ayungin larvae are very small, measuring just 1.8 mm in length. During this early stage, the larvae rely on live food organisms such as algae and rotifers for survival. And as they grow and transition to the juvenile stage, their diet shifts to brine shrimp (Artemia nauplii) and powdered artificial feeds for the next 60 days.

SEAFDEC on deck

Since 1973, SEAFDEC/AQD has been on a mission to produce sufficient viable fish seeds for food security and to provide sustainable livelihoods to small-scale fish farmers through the development of hatchery technology.

In 2019, the aquaculture department was granted the patent for the ayungin hatchery protocol by the Intellectual Property Center of the Philippines.

According to SEAFDEC/AQD chief Dan D. Baliao, the department is looking at bigger culture systems that would be suitable for the commercial production of ayungin, with the goal of scaling up food production and boosting the local fish industry.

The department wants to revive ayungin production and repopulate indigenous fish stock to support the “Balik Sigla sa Ilog at Lawa” program of the Bureau of Fisheries and Aquatic Resources.

From Laguna de Bay, wild ayungin are now translocated to nearby lakes such as Sampaloc Lake and Taal Lake. Others are reported in the freshwater lakes of La Union, Pangasinan, Quezon, Bulacan, Ilocos Norte, Ilocos Sur, Bataan, Oriental Mindoro and Pampanga.

Aya said SEAFDEC/AQD’s research efforts to domesticate ayungin are aimed at more than just increasing aquaculture production; they are also heading toward the possible replenishment of depleted seedstock in the wild.

“I am optimistic that, through the collective efforts of the academe, government and research institutions, the production of sufficient quantities of viable seeds of ayungin for restocking in natural waters may help increase the local fish biodiversity and secure food supply,” Aya said.

Fortunately, Aya’s optimism is leading to fruition with a growing interest among fish farmers to go into ayungin hatchery production. He said their office has received requests for ayungin seedstock. “This shows that there are now private individuals who are interested in helping to revive the production of this valuable food fish,” he said.

From fry to fortune

One such individual is John Aloria, who earned his bachelor’s degree in fisheries in 1979 and has sailed seas and oceans in pursuit of his profession. He travelled to Indonesia and Malaysia for tilapia culture and to Brunei Darussalam for arowana management. And from the Middle Eastern cities of Dammam and Jeddah, he flew to Ghana, West Africa, for tilapia fish cages management.

After a long time working abroad, he decided to return to the Philippines in 2015, and started his own ayungin hatchery and grow-out farm.

Aloria has tried the natural breeding of ayungin, but its unpredictable nature convinced him to switch to induced spawning. With his decision, he took a more controlled approach—but it wasn’t without its setbacks.

He spent three years of trial and error to successfully breed ayungin through the artificial method. He and his farm staff had no formal training in the method when they started. Seeing no noticeable fish life forming on the water’s surface, they would keep emptying the breeding tanks within two weeks—which, had they checked with the hatchery manual, was probably way too soon to call it failure.

“We always threw them out after one or two weeks of seeing no larvae or fry swimming. Until a time when one of my younger staff with sharp eyes told us that something clear and transparent was floating in the middle of the tanks,” Aloria recalled.

He didn’t believe the discovery at first. But three weeks later, visible body parts appeared from the clear, transparent larvae, and then the tanks began teeming with fry.

“Now, we have a lot of 45-day-old fry ready to sell,” he said. “We thank Dr. Frolan Aya of SEAFDEC/AQD for confirming to us that these clear-shaped larvae were actually ayungin.” 

A SEAFDEC-trained aquaculturist himself, Aloria now manages a total of 75 fish cages around Taal Lake and Sampaloc Lake, and in Jalajala, Rizal.

Aloria is currently the only commercial producer of cultured ayungin in the country, and his fish farms can produce around 20 metric tons of ayungin in a year. At 65, he has expressed readiness to retire. 

But for the meantime, he is waiting for someone “serious enough to take the job.”