The Leisure and Cultural Services Department probably over-reacted by closing 12 beaches across the city after Sunday's reported sighting of a whale shark off Lamma Island.
Beaches in Island and Southern districts were re-opened on Monday after no further reports of sightings.
Samantha Lee Mei-wah, a marine conservation officer with WWF Hong Kong, said the closure may have been unnecessary. 'The department could have over-reacted a bit,' she said. 'Instead of issuing warnings, the department could have made use of this opportunity to educate the public about sharks.'
Lee said whale sharks, which can grow up to 16 metres in length, feed on plankton and pose no threat to humans, unlike aggressive species, such as tiger sharks, bull sharks and great whites.
She called for new guidelines on shark sightings to avoid closing all beaches in future.
A department spokesman said the 'large' shark could have been a tiger shark. 'Although we could not ascertain the species, we considered it necessary to close the beaches to safeguard the safety of swimmers.'