Thirteen juvenile blacktip reef sharks were found dead yesterday in three fishing nets at Lazarus Island, south of Singapore.
More than 30 crabs of various species, some fish and a blue-spotted ray were also found in the gillnets. Several crabs were able to survive after they were disentangled and released by those who found them.
Marine enthusiast Rene Ong, who discovered the casualties, said she was out on a regular intertidal trip when she saw the nets.
They had apparently been laid out overnight by someone who had booked a chalet on St John's Island, which is connected to Lazarus Island by a link bridge.
"When I tried to remove the nets, the guys who placed them there came back. They were apologetic about the kill, but the damage was done," said Ms Ong, who spent about four hours disentangling the live crabs from the nets. Joining her in her efforts were staff and a student from the National University of Singapore (NUS).
She added: "They wanted the nets back, so I could not just cut the nets and release the animals. Thankfully, they agreed to let me have the sharks, and to release any catch that they couldn't eat."
The shark carcasses are being stored in a freezer at the St John's Island Marine Laboratory - part of the NUS Tropical Marine Science Institute. They will be passed to the Lee Kong Chian Natural History Museum for analysis.
Dr Tan Heok Hui, a fish expert from the museum, told The Straits Times that some sharks need to move in order to breathe. "Blacktip reef sharks are one of those that need to move constantly," he said.
"From the photo, (the dead sharks) all appear to be of the same cohort, as they are all around the same size. Some could even be siblings," he noted.
The find, although unfortunate, shows that Singapore's waters are thriving with marine life.
Mr Stephen Beng from the Marine Conservation Group of the Nature Society (Singapore) said the presence of apex predators, such as sharks, is a good indicator of a healthy reef.
He said that, since he first started diving here more than 25 years ago, blacktip reef sharks and bottom-dwelling bamboo sharks have been sighted at Singapore's reefs.
He noted that, now, with a sanctuary in the form of the Sisters' Islands Marine Park, their populations are expected to grow.
Added Mr Beng, who runs the Sea Hounds dive centre: "Gillnetting on shallow reef flats not only wipes out fish, but also physically damages the reefs. The relevant agencies should regulate recreational fishermen to ensure that they do not damage our reefs.
"While our Government tries its best to balance development with environmental sustainability, we can do our part by... educating fishermen about practices that put pressure on our limited reef resources."