Will a bigger beach and a safer fishhook help bring Hong Kong’s disappearing green turtles back?
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.”
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Chelonia mydas
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.