The dolphins appeared at about 8.33 am as the An Vinh Express 1 high-speed passenger boat was leaving the port, according to Phan Hau, 41, a local resident who was piloting the vessel.
Hau said he spotted the pod about one nautical mile from the shore. The sighting created an unusual spectacle for passengers and onlookers and was seen as a potentially positive sign for the local marine environment and fishing activity.
He said such a large group was rarely seen in the waters around Ly Son. In the past, local residents had generally encountered smaller groups of about four or five dolphins.
Nguyen Van Huy, chairman of the Ly Son Special Administrative Zone People's Committee, urged residents, fishermen and tourists to help protect the dolphins and avoid chasing, surrounding or approaching them too closely, as well as making excessive noise or otherwise disturbing their natural behaviour.
Huy also asked boats to slow down and maintain a safe distance when encountering the pod, while discouraging large numbers of vessels from gathering around the dolphins to film or take photographs.
Anyone finding an injured or stranded dolphin, or one showing unusual behaviour, should promptly notify the Ly Son Special Administrative Zone People's Committee and relevant authorities for guidance and assistance, he said.
“Protecting the dolphins not only helps preserve biodiversity and the marine ecosystem, but also enhances the island's natural landscape and environment,” Huy said.
He added that the presence of dolphins was also consistent with Ly Son's goal of becoming a green, friendly and sustainable tourist destination.