From pest to feast: The evolution of tilapia in the Philippines
(First of Two Parts)
Text and Photos by Henrylito D. Tacio
Tilapia, once regarded as a nuisance, has now emerged as one of the most favored fish among Filipinos. In fact, in terms of both production and popularity, tilapia ranks just behind bangus, the country’s national fish.
The Philippine Tilapia Industry Roadmap outlines a strategy for the sustainable advancement of the sector. In 2021, the Philippines ranked as the sixth-largest producer of farmed tilapia globally, with a total output of 281,111 metric tons, representing 4.80% of the worldwide tilapia production.
According to the Philippine Statistics Authority (PSA), approximately 93% of the total tilapia production originated from freshwater sources, while the remaining 7% was derived from brackish and marine environments.
Tilapia is very popular among Filipino consumers these days. (Tacio)
“The increasing interest in tilapia farming is attributed to its bright economic prospects, continuous research on the development of improved tilapia species, and the available commercial technologies,” the roadmap states.
Tilapia has gone a long, long way since it was introduced in the 1950s. Tilapia is a native fish to the freshwater habitats of Southern Africa. It is believed to be the fish that Peter caught in the Sea of Galilee, which was subsequently distributed to the crowds in Tabgha, an ancient town located on the north-western shore of the sea, by Jesus. This association is one of the reasons the fish is commonly referred to as “St. Peter’s fish.”
It was Deogracias Villadolid, of the then Bureau of Fisheries (now known as Bureau of Fisheries and Aquatic Resources), who brought some breeding stocks of tilapia from Thailand into the Philippines. Calling it a “miracle fish,” the bureau wanted it to be raised in backyard ponds nationwide.
But it took some time for Filipinos to accept tilapia as table fish. Muddy taste, unappealing color, and stories about it being bred in unsanitary waters were among the reasons why tilapia was initially shunned.
Farmers also avoided raising tilapia because of its high reproduction rate, which resulted in overcrowded ponds and stunted fish.
The cause of overcrowding was simple. Pond-reared tilapia, with a natural ratio of 50% male and 50% female, mature in 60 days. They breed frequently, often every 30 days. “Female tilapia may spawn from 100 to thousands of eggs, depending on its size,” reports the Iloilo-based Southeast Asian Fisheries Development Center (SEAFDEC).
Before they are sold in the public market, tilapia are first selected. (Rhoy Cobilla)
At such a growth rate, there were more fish in the pond and competition for food escalated. With reduced nutrition, the best attainable market size for tilapia at that time, after four months was only 150 grams.
“Tilapias are prolific,” says Dr. Rafael D. Guerrero III, former executive director of the Philippine Council for Aquatic and Marine Research and Development. Generally, tilapias spawn in shallow portions of lakes, rivers, or ponds. In breeding, the male builds nests on the bottom to attract females. The nests are round and shallow, about 20–25 centimeters wide.
“The male waits for the female partner in the nests,” SEAFDEC reveals. “After a brief courtship (to last a few hours), eggs are spawned by the female and fertilized by milt from the male. The female then gathers the fertilized eggs in its mouth to incubate them. The eggs hatch after three days. Spawning can occur as often as twice a month during the year if conditions warrant.”
Research indicates that male tilapia exhibit faster growth rates and larger sizes compared to their female counterparts. The most rational approach would be to cultivate exclusively male tilapia. However, the question arises: is it feasible to identify and separate male tilapia from females? Can this selection process be physically implemented for pond stocking? The answer is affirmative—this can be achieved through a method known as manual sexing.
Manual sexing involves differentiating male tilapia from females by examining a specific anatomical feature known as the urogenital papilla, located near the fish’s anus. In female tilapia, there are two openings, whereas male tilapia possess only one.
“Manual sexing is cumbersome and time-consuming,” said a publication published by the Department of Science and Technology (DOST). “Sometimes, the openings are not easy to see. The technique is only 80% accurate because of human error. Another disadvantage is that you can only sex fish when they are 3 months old. By then, they are almost fully grown.”
Fish cages: Tilapia are among the most popular fish raised via cages. (Tacio)
Dr. Guerrero, having dedicated over thirty years to laboratory and applied science, recognized the existence of a more practical, efficient, and cost-effective solution to the issue at hand. He examined the research of fellow scientists and discovered the idea of utilizing sex hormones to alter the sex of fish.
After nearly two years of investigation, he successfully transformed all tilapia in a pond into males by administering a synthetic male hormone—methyl testosterone or MT (a synthetic variant of testosterone)—during a specific period of their “sexless” stage. He termed this innovation sex reversal technology (SRT).
As much as 90% of the tilapia cultured in the country is sex-reversed, Dr. Guerrero said. “At least 50% of the tilapia produced in the United States, Canada, Israel, the Caribbean, and Asia is sex-reversed,” he pointed out.
According to Dr. Guerrero, MT is not deactivated once it gets into the stomach of the fish with the acid present, unlike the natural hormone which has to be injected. “The oral treatment with MT which, by the way, is used in human medicine for treatment of breast cancer, is only for 3–4 weeks during the sexless stage of the fry or the stage of sexual differentiation,” he explained.
After withdrawal of the treatment (about 92 hours), there are no residuals left in the system of the fish. “Since the fry are grown for at least 3–4 months for market and human consumption, it is very safe,” he assured. “There can therefore be no side effects if there is no synthetic hormone left in the systems of the fish.”
On the issue of what happens to the metabolites (excreted compounds) of the synthetic hormone once they are eliminated in the environment, Dr. Guerrero replied, “Can they affect other organisms and affect people? Studies have shown that in the tropics, the high temperature and the effect of sunlight breaks down the metabolites into simpler compounds through biodegradation and photo-oxidation that have no effect on humans.”
Dr. Guerrero said there are studies in the Philippines and other countries that endocrine disruptors from plastics and insecticides in the environment can influence the direction of sex of fishes and possibly humans who consume them towards femaleness or hermaphroditism. Not maleness. “MT, which is for maleness, is therefore not in question,” he stressed.
In recognition of his contributions, Dr. Guerrero has received numerous accolades from various awarding organizations. In 2004, he was honored with the Mgr. Jan D.F. Heine Memorial Award by the International Tilapia Foundation.
Dr. Guerrero used synthetic male hormones to convert female tilapia into male tilapia. However, a study conducted at the Central Luzon State University (CLSU) showed pollen from pine trees may do the same trick.
“The use of pine pollen in its unprocessed condition enables the change of sex of young fishes used for breeding, turning in 84.59-90.46% males,” said Dr. Ravelina R. Velasca, of CLSU’s Freshwater Aquaculture Center, who headed the study.
Unprocessed condition means the pollen still has a protective cover. “The use of pine pollen technology in tilapia sex change eliminates health hazards associated with all-male tilapia production,” she explained. “It is an environment-friendly approach and could be an alternative to the use of high-priced standard hormones in sex change.”
The advantage of CLSU’s pine pollen technology lies in its ability to prevent the accumulation of harmful chemicals in pond soil, a common issue associated with conventional synthetic hormones.
Dr. Velasca said that utilizing this natural product enhances the management and standard practices of tilapia farming. Pine pollen, which is the male reproductive component of the pine tree, has been found to be a rich source of plant-derived testosterone.
“Both male and female reproductive organs are present in the same tree,” Dr. Velasca explained. When consumed in powdered form or as a liquid solution in alcohol, pine pollen is readily absorbed by tilapia. (To be concluded)
