Nguyen Van Khanh used to be known as "The Dugong Slayer of Phu Quoc."
He learned how to fish dugong from his father when he was 19 and quickly earned a strong reputation among the island's fishermen.
From his start as a teenager until 2002, Khanh caught some 200 dugongs, said the 44-year-old retired fisherman.
Over 20 of the mammals Khanh caught weighed more than 800 kilograms, he said, adding that normal-sized dugongs weighed an average 150- 300 kilograms.
He said his father, who was also a famous dugong hunter on the island, had caught even more dugongs in his lifetime.
But the International Union for Conservation of Nature and Natural Resources (IUCN) lists the dugong as "vulnerable to extinction" due to overhunting and pollution.
The mammal has already disappeared from several of its natural habitats.
"If my family caught 500 dugongs alone, then Phu Quoc fishermen must have caught into the thousands," said Khanh.
Change of heart
But Khanh no longer hunts dugong, and their endangered status is only part of the reason.
He said he stopped dugong hunting in 2002 due to a more personal experience.
"I saw a baby dugong squealing, like it was crying, while watching its mother entangled in our net," he said. "The mother couldn't do anything but stare back at its child with sad eyes."
Khanh said he had known about the mammal's deep maternal love since he started hunting, but this was the first time he experienced it first hand.
Nguyen Van Khanh, once dubbed as "the dugong slayer of Phu Quoc," shows off two of the animal's tusks he keeps as mementos. Khanh now works to protect the vulnerable dugongs from illegal hunting.
"I then swore not to hunt dugong anymore."
That same year, the southwestern Mekong Delta province of Kien Giang, which includes Phu Quoc, banned the hunting of rare sea species, including dugong.
Khanh then began working for a World Wild Life Fund marine conservation project on the island.
'Debt to the sea'
Every day, Khanh visits local fishing villages to promote awareness about protecting rare sea animals.
He said that many former dugong hunters had stopped hunting after the ban. But he also admitted that some still fished dugong illegally. The mammals are hunted for their bones, tusks and meat. A pair of tusks can cost between VND10-15 million (US$563.06-844.59).
"I advise any person who is still hunting for dugongs to quit," said Khanh. "Some listen to me, but others get angry with me, saying I'm poking my nose into their business ...but I'm not discouraged, because this is how I pay my debt to the sea."
Although the current total population size of dugongs is unknown, a 2003 study conducted by sea animal expert Professor Helen Marsh said the number of dugongs was decreasing in at least 21 out of the 37 nations surveyed.
The study also said that the lady of the sea had vanished in at least three islands groups where it was formerly found in abundance.