The wild otter pup seen last Saturday with a fish hook lodged near its eye has now been spotted free from it.

It was seen near Kallang Wave Mall on Wednesday morning by an informal group of otter watchers, who have been checking on the animal and photographing it daily since its injury was reported.

It is not clear how the hook came off. It could have been pulled out by another otter in the family, said one of the otter watchers, 34-year-old engineer Nick Soo, who goes by the moniker, Fast Snail, in a Facebook post on Thursday.

In all, about 10 otter watchers took more than 10,000 photographs and videos of the otter family over five days. They spent days poring over the photos and videos, looking closely at the details of each of the five pups in the family, to verify that the hook had come off.

Although the pup's eye seemed reddish and slightly swollen, it was behaving normally, eating and following its family around, said another of the otter watchers, Ms Yane Kang, 40.

Mr N. Sivasothi, a senior lecturer at the National University of Singapore's department of biological sciences who has studied otters, said the hook could have been dislodged when the otter rubbed its head against another surface.

"Otters move and twist their bodies against the soil where they defecate and mark the ground, and against one another in the water."

Mammal researcher Marcus Chua from the Lee Kong Chian Natural History Museum cautioned that although the hook has been removed successfully in this case, the mammal could have hurt itself in the attempts to remove it.

"(Otters') manual dexterity is not as good as ours, so (in such cases) the hook can still be transferred to their tongue or lodged in their paws," he said.

Environmental groups have called out irresponsible and illegal fishing activities as a risk to wildlife and people. This latest case of otter injury is the third since last October.

Ms Anbarasi Boopal, director of the Animal Concerns Research and Education Society's (Acres) Wildlife Rescue Centre, said the society is relieved that the hook has come off.

"Acres is thankful to the otter- watching community for its monitoring and updates," she said.

"We hope there is increased awareness of the plight of wildlife that suffer from such illegal and irresponsible fishing activities in our water bodies, (and) we urge the public to report illegal fishing activities to the authorities."