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Monday, April 25, 2005
Hopes high on revival of diwal production
THE angel wing clam (Pholas orientales), popularly known as diwal in Hiligaynon, is known in the Visayas as the most luscious, delicious delicacy.
The large, mud-burrowing bivalve is native to the tidal mud flats of Panay and Negros Islands.
Because of its large size, juicy meat and sweet taste, diwal, endemic to Western Visayas only, has been one of the most expensive and most sought after bivalve in the Philippines.
The name diwal came from the habit of the clam in extending its long siphon, out of the mud when feeding on minute plankton in the seawater column.
Thirty years ago, when Villa beach in Iloilo was a long stretch of tidal flat that is very conducive for swimming and has a very clean beach water, the nipa cottages along the long beach serves a very sweet and large clam known as diwal.
Its taste is so fresh and milky and the juice is tangy and when swallowed leaves a taste of sweetness. It is an ordinary food on the table and the markets are swarmed with these palatable delicacy.
Then slowly, this delicious diwal can no longer be found in the market.
According to the research study of Nova Pacific Research Institute at the University of the Philippines-Visayas Science Park in Miag-ao, Iloilo, diwal was abundant in Roxas City, the Seafood Capital of Western Visayas, notably in Barangay Bara, Capiz.
It can also be found in Pontevedra and Hinigaran, Negros Occidental.
However, there had been a dramatic decline in population of diwal in both islands beginning in 1990.
As reported in the research paper, diwal is now nearly extinct in Barangay Bara, Capiz and rarely found elsewhere. The reason for this phenomenon remains unknown.
Probable causes of such decline were attributed to the destruction of most marine life forms due to over harvesting, pollution, siltation and destruction of the marine ecosystems.
These bivalves are also known to thrive only in clean surroundings. The research on the life cycle of diwal is difficult because there had been no published scientific data on its biology and ecology.
A geographic distribution survey was conducted by Romeo Fortes of the University of the Philippines in the Visayas.
In 1993, Dr. L. Laureta of the Institute of Aquaculture, U.P. Visayas College of Fisheries pioneered on artificial spawning of diwal under the auspices of the Department of Agriculture's Fisheries Sector Program.
The research on this important bivalve in Western Visayas is a "race against time."
According to Jonathan R. Matias of Nova Pacific Research Institute "one must learn as fast as possible the critical information about the life cycle of the endangered organism before one loses the opportunity to do so because of extinction".
At the Seafdec research laboratory at Tigbauan, Iloilo in 1994, the once very large diwal were already crawling on different congested tanks separated by sizes.
The research is also part of the efforts in saving what is left of the famous diwal and hoping that through scientific interventions, the bivalve can again be abundant in the tables not only of the rich who can afford its price but also a delicacy at the poor man's table.
From 1994 to 1995, diwal was still being sold at the seaside restaurants of Pulupandan but on a much reduced size just like the size of an ordinary tahong.
Nowadays, one can rarely see diwal being sold in small eateries and even in big restaurants.
According to Dr. Jessie Ronquillo, the Nova Pacific has now the capability to grow millions of diwal from fertilized eggs to post-set larvae ready for re-introduction to coastal habitats.
What needs to be developed is more information about their survival from post-set larvae to adults in the natural environment.
This information is easier to be gathered than making a research on culturing the eggs through the critically sensitive embryonic and larval stages.
With this scientific breakthrough, there is a need to understand the biology of the angel wing clam.
Basic research in developmental biology, ecology, effects of pollution, behavioral biology and other aspects will hopefully deliver diwal into the marine ecology of Negros and Panay again.
(April 25, 2005 issue)
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