MANILA - Larger fish species are expected to return to Manila Bay once clean-up efforts succeed, researchers from the National Fisheries Research and Development Institute (NFRDI) said Tuesday.

“Before we had large fish. These are more expensive, unlike the ones (local fishermen now catch) like sardines that are cheaper,” said Grace de Veyra-Lopez, NFRDI science research specialist.

“Once we rehabilitate (Manila Bay), the demersal fish will increase again.”

De Veyra-Lopez said this will benefit fishermen who can earn more from bigger catch.

Demersal fish are those that live near the bottom of the sea. These include groupers (lapu-lapu) and threadfin bream (bisugo).

At a press conference with environmental groups, including Oceana Philippines, on the impacts of the Manila Bay reclamation, De Veyra-Lopez shared research on how demersal fish dominated the Manila Bay area from the 1940s until the 1960s.

However, later studies noted a “change in species dominance,” or an increase in the proportion of pelagic fish, such as sardines, which live near the water surface.

This, she said, is because of the pollution in Manila Bay, allowing only those who live near the water surface to survive.

Elsa Furio, another NFRDI science research specialist, explained that domestic waste dumped into Manila Bay causes harmful algal bloom.

When the blooms die off, they decay and fall to the ocean surface, consuming oxygen. With low oxygen levels and the resulting increase in hydrogen sulfide, bottom-feeding fish are unable to survive.

Furio said hydrogen sulfide generates the rotten egg smell that people get a whiff of along Roxas Boulevard.

It would be a “dream come true” if Manila Bay is truly revitalized through the inter-agency campaign ordered by the Supreme Court, Furio said, adding she hopes it would be safe again to swim in the bay.

• SC orders govt agencies to clean up Manila Bay

Asked about the impact of reclamation on the bay, Furio said, “For me personally, when it comes to reclamation, that is totally bad.” She explained that while dredging helps remove harmful sediments on the sea floor, dumping soil for the reclamation can disturb the spawning ground of fish.

She said it would be unfortunate if the improving condition of Manila Bay would be affected by any reclamation.

President Rodrigo Duterte earlier said he is unlikely to approve reclamation projects in Manila Bay, although the Philippine Reclamation Authority already gave notices for four projects to proceed, subject to value engineering approval.

Duterte said reclamation projects will need to have an audit for waste management, if he is to support it.

• 'Not in my time': Duterte nixes proposed Manila Bay reclamation projects