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As tension in the West Philippine Sea continues, Filipino fishermen revealed that Chinese vessels are mass harvesting giant clams in Scarborough Shoal.

When Michael Bernal's small boat came back from spear-fishing one morning, his catch was noticeably smaller than the day before.

When asked for the reason, he said it may be because of the cloudy water due to people scouring for giant clams in the area.

"Wala pa sa kalahati yung nahuli namin ngayon...dahil doon sa malabo yung tubig sa loob. Saka 'yung nagva-vacuum, 'yung naghuhukay ng taklobo," he said.

(What we got today did not even meet the half of our usual catch. Maybe because of the cloudy water due to the people scouring for giant clams.)

Filipino fishermen have been watching the Chinese giant clam extraction go on for years at Scarborough Shoal. The workers come from wooden trawlers which are capable of lifting small boats on large nets and bear the flag of China.

Speed boats of the China Coast Guard that visit trawlers drive away Filipino and other fishing vessels trying to enter the shoal.

In the morning, workers leave in small boats. Some wear wet suits, others wearing distinct hats.

ABS-CBN News found one of the boats anchored in Scarborough Shoal. It seemed abandoned but its engine was actually running and there were tubes extending into the water.

Filipino fishermen said they've seen this many times.

"Diba yung elesi may hangin yun, Ma'am? Parang siguro 'yun kasi karamihan sa kanila mayroong tubo na mahaba baka 'yung ang pinakaextension nila ginagamit para makayod' yung lupa ba. Para 'yung taklobo mahukay nila ba," fisherman Norman Torres said.

(The propellers produce bubbles, right? Most boats have long tubes which they use to scour the seabed and get the giant clams.)

ABS-CBN News also went to a site where the workers stacked the shells of the giant clams before hauling them out to the trawlers.

Pile upon pile of dead giant clams, each batch marked distinctly with yellow, green and red labels.

Fishermen said this is just one of the sites and that the piles were actually still small. After a few days, the top of the said piles can already be seen above water.

They also said this operation is already taking its toll on the much smaller spear-fishing and net-fishing that they do.

"Yung tubig lumalabo. Hindi ka rin masyado maka-ano sa gabi kasi malabo na nga makati pa. Magkasugat sugat yung katawan mo dahil sa kati, magmaga, ganoon," Torres said.

(The water becomes cloudy. You cannot also fish at night because it is really cloudy and can cause itches. Your body might get wounds or swelling because it's really itchy.)

They are also beginning to worry about the fate of Scarborough Shoal itself.

"Matira para diyan sa akin ay buhangin balang araw. Kasi araw araw ba naman silang kukuha diyan, huhukayin nila. Mga bagong tinubo na Pilipino wala na silang madatdatnan dito balang araw.," fisherman Romulo Etac said.

(One day, all that will be left there will be sand. Every day, they get something from there. The younger Filipinos will no longer see and find anything here one day.)

There are only two of these trawlers when the team first came to Scarborough Shoal, but now, there are eight big boats which continue to extract giant clam shells under the water.

Fishermen said this isn't the biggest number of boats they've seen this far.

As of today, there are no less than 14 Chinese vessels in the area. Each one, fulfilling its tasks in Scarborough Shoal, unhampered.