The angel wing clam (Pholas orientalis), known locally as diwal, which in the local Hiligaynon language means “that it sticks it’s tongue out”, is a species of benthic bivalve that lives in the estuaries or near the mouth of a river mainly in Roxas City, Pan-ay, in Capiz Province and the central Negros Occidental area and in particular around Valladolid, Palupandan, San Enrique, Pontevedra, Hinigaran and Binalbagan.
Ideally its habitat is found within the depths of clay or silt soils, but it also lives in the under layers of sandy and muddy terrains and thrives near the mouths of rivers. It is presumed that the eggs of this species are laid between June and August. Different methods are used to collect the clams depending on the depth of the water, the distance of the collection site from the shore and the type of soil that it is found in. When the water is deeper and at least 0.5 kilometres away from the shore, divers use boats. At sites that are found closest to the shore, bamboo poles are driven into the seabed which can be used to hold onto when diving to harvest the clams.
The first reports that have been found which talk about the presence of diwal in these areas, date back to 1938. Until the 1970’s it was not a very well known product, however from the 1990s onwards the demand has increased considerably, resulting in excessive harvesting and the risk of habitat destruction due to trawling and water pollution, which is caused by chemical discharges from shrimp farms, rice fields, sugar plants, alcohol and liquor factories. The depletion and the progressive decline of the clam’s population in all areas has also led to a ban on its harvest in the Capiz area, on the island of Panay, where there were breeding areas.
Today only the inhabitants of Valladolid are allowed to collect diwal, from January to April, through the use of a permit. They are collected between 6 and 10 in the morning, with divers going up to 8 metres under the water. The ideal size of diwal is 5 centimetres.
In 2006, the Negros Occidental province and the Central Negros Council for Coastal Resources Development (CENECCORD) have started a repopulation project with the support of the Visayas University of the Philippines. Diwal sanctuaries have been established in the CENECCORD area and since 2008 the species has started to recover. To protect it, a resolution was passed that regulates collection limits, as well as prescribing open and closed seasons in areas that are also outside of the sanctuaries.
Despite these initiatives, one of the biggest problems in regard to fisheries management remains the lack of resources to enforce strategies and regulations to protect the diwal population and ensure its sustainable production and use. Conservation of the resource is a value that is not yet fully understood by many fishermen. In fact, there are still many reports of illegal fishing, from night poaching during the season that is closed to trawling. Trawling is still practiced in some areas, which heavily depletes stocks and contributes to the decimation of populations of newly hatched clams.
The traditional way to eat diwal is to cook them on the grill after brushing the shells to remove dirt and slicing and washing the clams to remove the sand. They are also grilled and accompanied with laswa (a vegetable soup) or stewed vegetables and can also be steamed with lemongrass and ginger.