The Grampian force has appealed for help in tracing two male jet skiers who were seen close to the pod of cetaceans on the last week. One of the jet skis was red and white, while the other was green and black in colour.
Dave MacKinnon, a wildlife crime officer with Grampian Police, said:
"There is legislation which protects cetaceans – which includes dolphins – from intentional or reckless disturbance or harassment.
"People who own or use jet skis in the North-east stand a good chance of coming into contact with these animals, and it is important that they understand how to behave around them to ensure they stay within the law.
"The general advice with regards jet skis and boats is not to approach within 50 metres, cut engine speed and do not chase or follow these animals."
Sue Edwards, of Seawatch Foundations, warned: "All dolphins are at risk when being driven at by irresponsible jet ski riders. Dolphins at the harbour have enough to deal with from ships, safety boats and pilot boat traffic coming in and out of the harbour."
She added: "Aberdeen harbour mouth is one of their main feeding places along the east Grampian coast and these dolphins have small calves with them at any time of year."