Cllr Farquhar said, “There are a few totally irresponsible jet-ski riders who have been causing problems.

“The machines they ride are capable of 80mph, and there is a very real danger they could distress the dolphins using the River Tay.

“People have been enjoying seeing the dolphins all summer, and it would be a great pity if the actions of a few individuals chased them away.

“There are no licence requirements for these craft, and these individuals have a complete disregard for other people using the water. In most cases they will have had no training in the use of these powerful machines, and no safety advice.

“They also come in close to the beach and the water where people are swimming, and this can be a very frightening experience for people who are out there to enjoy themselves.

“We will be continuing to work with Tayjet Personal Waterfront Club, who represent the extremely responsible enthusiasts who use the water safely, the port authority and other agencies to deal with the problem.”

Rogue jet-skiers have given cause for consider-able concern over recent months, and their erratic riding is endangering themselves, other jet-skiers and swimmers.

It emerged last month that a swimmer from the Ye Amphibious Ancients Bathing Association was almost beheaded by a jet- ski.

Tayjet have a dolphin, whale and porpoise policy and code of conduct, to ensure the public and marine mammals can share the water safely.

The policy states, “It is recognised that many people at sea for recreational purposes will wish to enjoy encounters with cetaceans.

“However, these encounters pose a potential threat to cetaceans unless they are conducted in such a way as to minimise disturb-ance.

“Collisions with boats or jet-skis may result in injury or death of cetaceans; engine noise may interfere with their acoustic communication, prey detection and orientation systems; and, erratic patterns of movement of boats may cause the animals to suffer stress.”

Tayjet said that if the dolphins are stressed, their natural behaviour could be disturbed and result in them moving to other areas, and could disrupt mother and calf bonds.

The club has adopted guidelines to minimise disturbance and maintain a healthy dolphin population.

The code of conduct recommends that jet-skiers who encounter dolphins should continue at a slow, steady speed under five knots, avoid coming between mother and calf, allow groups of cetaceans to remain together, and avoid driving through groups of cetaceans.

Councillor Farquhar added that work was expected to be completed this month on a new watercraft channel near the castle, allowing better separation of powered craft and the public using the beach.

The cleaner waters of the Tay seem to have acted as a magnet for increasing numbers of dolphins and minke whales off Broughty Ferry in recent months.

Sightings of several pods of bottlenose dolphins have become a common occurrence, while the presence of minke whales, which can grow up to 30 feet, have delighted residents and holiday-makers alike.

The dolphins started to arrive several years ago, their presence mirrored by decreasing numbers in the Moray Firth.

It is thought pollution and noise from rising numbers of dolphin-watching tourist boats drove the creatures from their habitat there and down the east coast.

Some scientists believe the recent heatwave drew the animals south from colder, more northerly waters, while others say the £140 million Tay clean-up via the Hatton waste-water treatment plant has given the mammals a more welcoming environ-ment.