BOLINAO, PANGASINAN— Twice a week, Julio Curiano Jr. would hop into a speedboat and head for a 5.8-hectare ocean nursery of giant clams off Silaqui Island at the northernmost tip of this town facing the West Philippine Sea.
Read the special report on saving Pangasinan’s giant clams here: PLAYGROUND OF GIANT CLAMS
A maintenance man of the University of the Philippines Marine Science Institute’s marine laboratory here, Curiano spends his day checking on the thousands of giant clams like they are his own children.
He first inspects the baby clams, also called juveniles, that are having their first taste of the sea after spending months in a hatchery. “I measure their shells and clean them and their cages to ensure their growth and survival,” he said.
The biggest clam in the nursery is a 98.3-centimeter long Tridacna gigas and the shortest is a 3-cm juvenile. The gigas—the largest among the world’s giant clam species—can grow to more than a meter long. The longest clam recorded so far is 136.9 cm.
Curiano then takes water samples and measures their salinity, temperature and dissolved oxygen levels. The clams can only survive in water with salinity ranging from 28 to 32 parts per thousand and within a temperature range of 28 to 30 degrees Celsius.
“The average temperature here (in the nursery) is 30 degrees Celsius and the average salinity is 29 ppt. This is why this is an ideal site for a giant clam nursery,” Curiano said.
If it gets too hot, especially during summer, he patiently moves the clams to a deeper part of the reef.
The reef is also protected by a natural breakwater, preventing waves from the West Philippine Sea from disturbing the stocks.
The Silaqui reef is also shallow, with its clear waters only 2 to 3 meters deep, just enough for sunlight to penetrate the sea. Sunlight is important because giant clams have algae in their mantle that use sunlight to produce food for the clams through photosynthesis, Curiano said.
“I know all the clams’ birthdays and where they can be found in the nursery,” he said.
The nursery hosts 35,684 adult giant clams and 11,209 juveniles, which are arranged in straight lines in six areas of the reef.
According to Curiano, the giant clams’ birthdays are useful during spawning seasons because these guide him to the clams that should be induced to release eggs and to those that should release sperm for fertilization.
As hermaphrodites, the clams’ sperm and eggs should not come from the same clam to avoid inbreeding, he said.
“I’ve been in this job since 2006. I love this job,” he added.