Heads Above Water: Why Are Hong Kong's Green Turtles Disappearing?
On October 10, Lam, a green turtle found tangled in a fishing net in Lam Tsuen River in Tai Po, was rushed to Ocean Park’s rescue centre within the amusement park’s Aberdeen campus. An X-ray scan showed a fishhook puncturing its esophagus. There was trauma to its shell. Part of its left fin was marked with a deep, v-shaped cut. Lam passed away 19 days later from the injuries.
“We did a post-mortem exam and the pathologist found some abnormal things inside the body,” says Ocean Park vet Sarah Churgin, who was still waiting for an autopsy report a week after Lam’s death when we interviewed her at the centre.
Lam was Ocean Park’s fifth rescued green turtle this year and one of the victims of a series of mysterious deaths, including that of a juvenile green turtle spotted by beachgoers on October 7 at a Cheung Chau beach and another a week later at Gemini Beach in Sham Tseng, prompting questions about what is killing Hong Kong’s green turtles and what the city should be doing to protect them.
“The organs [of the Cheung Chau and Sham Tseng turtles] were too autolysed [decomposed] for us to tell the exact age and cause of death,” says Brian Kot, the head of the Aquatic Animals Virtopsy Lab at the City University of Hong Kong, who was called in along with the Agriculture, Fisheries and Conservation Department (AFCD) to examine the turtles. The contents found in the Sham Tseng turtle’s intestines are now kept in two bottles in Kot’s lab: plastic gloves, plastic bags, food wraps, drinks packaging and ropes.
Sadly, rubbish has become a common “diet” for green turtles, which are classified as endangered by the International Union for Conservation of Nature. Over two decades, Ocean Park has rescued more than 100 of them: 74 were released back into the wild; the rest did not survive. “Many turtles come in with plastic ingestion and intestinal blockages,” Churgin says. “Plastic bags look like jellyfish and plastic strings and fishing line look like seaweed and grasses that they eat.”
The green turtle, scientifically known as Chelonia mydas, is one of the largest species of migratory sea turtle, and the most common of the five species recorded in Hong Kong. They are named for the green layer of fat beneath their shells. Juvenile green turtles feed on invertebrates such as sponges, crabs and jellyfish. Unlike most sea turtle species, they become herbivores when they mature and eat algae and sea grasses.
Simon Wong, AFCD’s wetland and fauna conservation officer, says that green turtles are megafauna with a long lifespan, which means they consume various kinds of food and play an important role in balancing the ecosystem.
“Plastic cannot be digested. It fills up their stomach space and makes the green turtles feel full. In the end, they suffer from malnutrition,” adds Kot.
Since the start of the turtle virtopsy project last August, which employs scanning and imaging technologies to complement traditional autopsy, Kot has analysed seven green turtles. He discovered that it isn’t always easy to verify whether the ingestion of plastic waste is the direct cause of death, as pneumonia, parasite infestation and injuries from manmade hazards such as propeller blades are also quite common.
Gloria Lai, senior conservation officer at WorldWide Fund for Nature (WWF) Hong Kong, believes manmade hazards are a likely culprit. “The injuries made by traditional long, J-shaped fishhooks are most of the time fatal,” says Lai.
Green turtles aren’t actually the target of fishermen, but are often accidentally caught by the long lines used in large-scale fishing, especially in Vietnam’s lucrative yellowfin tuna industry, which uses bigger and therefore more damaging tools than those in Hong Kong.
Operation: Save The Turtles
There’s hope, however. Since 2014, WWF-HK and its Vietnamese counterpart have been collaborating on the Fishery Improvement Project, which has replaced about 15,000 J hooks with C-shaped hooks for 150 participating fishing boats.
“Circular hooks are less likely to be swallowed and are the most effective way of preventing the bycatching of sea turtles,” says Lai. Before the project, one out of every 400 sea turtles was caught by the J hooks. Vietnamese fishermen have reported to her that there have been fewer bycatches since they started participating in the project.
Green turtles, the only species that nests in Hong Kong, face a different threat, even before they hatch. Satellite tracking shows that the Hong Kong nesters travel between Hong Kong, Hainan in China and Dao Bach Long Vi Island in Vietnam. Every nesting season, from June to October, green turtles return to their place of birth, some in Hong Kong, to lay eggs. According to Andy Lau from Ocean Park’s animal care team, Hong Kong is an important “middle place” for the long-distance sojourners to nest and rest.
A 2014 paper published in Pacific Science suggested that green turtle eggs were extensively harvested for a few decades, leading to the depletion of the local population in the 1990s. In 2000, when AFCD started monitoring the local population, there were just three females laying eggs, about 120 each, at Tung O and Sham Wan on Lamma Island, as well as at Big Wave Bay in Shek O. In the following two decades, only seven were sighted, in Sai Kung and Sham Wan. While green turtles were still spotted from time to time foraging in Hong Kong waters, the last sighting of them nesting happened on Lantau in 2016, and none has returned since to lay eggs.
Wong observes that there has been more boating activity near the nesting beaches, especially around Sham Wan, the last main breeding ground in Hong Kong. “Breeding green turtles stay in the waters adjacent to their nesting sites,” he says. “During this period, they are particularly sensitive to disturbance from human activities such as glare, noise and marine traffic, which may cause them to abandon nesting.”
That doesn’t mean all green turtles are gone for good. They are occasionally spotted at the seaside or by divers. “This year my friends told me they have seen green turtles, and from time to time there are media reports or citizens posting on Facebook about sighting green turtles,” says Angel Lam, oceans conservation manager at WWF-HK. “To better protect the remaining turtles, we discourage people from having junk boat parties at Sham Wan. There are still many other beautiful bays that holiday seekers can use.”
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Churgin, the Ocean Park vet, points out that threats faced by green turtles also indicate a bigger marine crisis, noting injuries that have afflicted many cetaceans, including Chinese white dolphins and finless porpoises.
“Moreover, every single type of marine life is full of plastic when you look inside their stomachs, including whales, dolphins, all kinds of birds, seabirds and fish,” she says. Rising sea temperatures have also caused a shift in incubation that favours female turtles. WWF Australia reported in 2018 that there were virtually no male northern green sea turtles being born in the Great Barrier Reef.
Both Lai and Chrugin think that to rescue green turtles and other marine life, everyone should be playing a part in tackling the global problem. “What ordinary people can do too is to reduce single-use plastics. If you’re out on the water or in a boat, make sure you know to avoid sea turtles. Be diligent and responsible,” says Churgin.
The government, too, has decided to take greater actions this year. Since 1999, access to Sham Wan beach has been restricted for several months each year, with a new proposal to extend both the duration and size of the area beginning in April 2021, when the new nesting season begins.
That will be the 24th nesting season since AFCD first artificially incubated hatchlings in Sham Wan in 1998, doing so until 2012, when the last successful nesting was documented. As of today, more than 1,000 hatchlings from Sham Wan, either naturally hatched or artificially incubated, have returned to Hong Kong waters. “Green turtles take at least 20 years to mature before they reproduce. It’s about time,” says Kot.
“It’s a fact that there aren’t any green turtles nesting in Hong Kong any more, and we aren’t sure if these released Hong Kong turtles can make it back next year, but it’s best that we get prepared, if and when they return.”
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