tilapiaMANILA — A fisheries expert has claimed that most of the tilapia being consumed in Metro Manila are genetically modified (GM) because these are sex-reversed at the fry stage.

Virgilio Marzo, who graduated with a fisheries degree from the University of the Philippines (UP) in Diliman and trained in Aquaculture and Fishery Technology at the Fisheries Research Institute (TFRI) in Keelung, Taiwan, had a study tour on tilapia hatchery management in Saudi Arabia.

He majored in aquaculture and also participated in a rural development seminar and workshop with emphasis on fisheries in Germany.

Marzo said that most consumers are not aware that “what they are buying from the market are GM tilapia since these are sex-reversed at the fry stage by methyl testosterone (MT).”

He said that his tilapia fry are not sex-reversed and are fed with the nutrient Omega-3 and some Omega-6, both of which are needed by humans and fish. “The ideal ratio of Omega 3 and 6 in our body should be 1:5,” Marzo added.

More than 70 percent of the fish consumed in the National Capital Region (NCR) comes from the Laguna de Bay, where the feminization of the bighead carp had been scientifically proven by Dr. Michelle Grace V. Paraso in a study she conducted in 2011 at the University of the Philippines at Los Banos (UPLB). The same study was financed by the Southeast Asian Regional Center for Graduate Study and Research in Agriculture (Searca.)

Paraso discovered that the sex change was caused by the estrogen-laced human urine that end up contaminating the lake. Results showed the presence of a natural estrogen called 17-beta estradiol (E2).

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“Alarmingly, the levels of E2 found in Laguna de Bay were much higher than those in surface waters in other Asian countries,” Paraso said.

These bio-pollutants are correlated to the hormone excretions found in animal and human feces and urine carried as surface runoff into the lake.

Paraso said that untreated sewage and urine dumped into Laguna de Bay have caused male carps to acquire egg yolk protein precursor and have lesions in the testis.

She warned this could potentially affect the health of fish raised in cages and pens in the lake, destabilizing the balance of male and female fish in the waterway and eventually causing diseases that could depopulate the lake.