SINGAPORE - A National University of Singapore (NUS) sailing trip, organised as an experiential learning initiative, has come under scrutiny after photos of students posing with giant clam shells collected during trip drew flak online.

Earlier this month, 12 NUS students and alumni had sailed out to Indonesia's Riau Islands on a 60-foot (18m) schooner for seven days with Associate Professor Martin Henz, who teaches at the university's School of Computing and Faculty of Engineering. The group, which included students from various faculties - such as business, geography and computing - had returned to Singapore with several shells and a giant clam shell as keepsakes from the seven-day trip.

But a photo of them posing with the shells in a Straits Times article on Monday (Jan 30) sparked a debate online.

Environmental groups and researchers pointed out that the giant clam is a protected species under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (Cites), and that proper permits are needed before any animal parts can be imported across borders, even if these are dead clam shells. Removal of other shells that had washed ashore could also be a threat to the eco-system.

Among those who had criticised the group's actions was Mr David Tan, 27, a researcher from the Evolutionary Biology Laboratory at NUS, who said that it was "alarming" to see that the group had brought the clam shell back.

"One of the stated objectives of the programmes was to encourage a love for nature... but this ran entirely counter to it.

"It's sad that there wasn't really anyone who was able to provide guidance (on conservation) for this trip, especially when it seemed like a ripe opportunity for this kind of education to occur."

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Prof Henz, an avid sailor who has taken NUS students on sailing trips in the region since 2013, said that the sailing trip was initiated to "provide our students with a unique out-of-classroom learning experience".

"The voyage team had picked up a few dead shells that were washed ashore, and the team was not aware of the international guidelines on collection of shells which would be applicable even if they are dead shells.

"This has been a learning experience for all involved, and we will be more mindful of our actions in the future to not leave anything behind nor remove anything from nature."

Professor Peter Ng, head of Lee Kong Chian Natural History Museum, said that he has spoken to Prof Henz about the concerns raised and is working with the group to hand over the shells to the relevant authorities.