Bottlenose dolphins exist along the length of the Welsh coast and not just in Cardigan Bay as previously thought, according to a new survey.
The dolphins not only exist in Cardigan Bay, say marine experts
The Sea Watch Foundation said the perception that large numbers were only found in the bay was wrong.
The foundation's National Dolphin and Whale Watch recorded sightings off Pembrokeshire and Anglesey last week.
Experts said a European Union habitat protection order may now have to be extended.
The foundation is now recalculating Wales' bottlenose population, which was previously estimated to be about 140.
Its survey ran from 13 to 21 August, when the British public was asked to record sightings of whales and dolphins.
Dr Peter Evans, head of research at the Sea Watch Foundation, said: "Our original perception was that resident populations of this species occurred in Cardigan Bay and the Moray Firth, with a small one also along the south coast of England, and that dolphins seen in other regions were strays that had wandered there for short periods.
"The dolphin watch has blown that idea away completely.
"It has shown that bottlenose dolphins are widely distributed throughout the Irish Sea from Pembrokeshire north to the north Welsh coast and beyond - even to the Solway Firth."
Dr Evans, from the zoology department of Oxford University, added that there may be several populations rather than just offshoots of the Cardigan Bay population.
"This has very important implications on conservation and management of the species," he added.
"It means that the marine Special Areas of Conservation established under the EU Habitats and Species Directive in southern Cardigan Bay and at Pen Llyn a'r Sarnau alone, will not protect the species since it ranges over much wider areas where it can experience other local threats."
It has been a successful summer for whale and dolphin watchers.
Last month, humpback whales were spotted in Cardigan Bay for the first time.
And last week 2,000 common dolphins were seen off the Pembrokeshire coast and days later a school of giant fin whales was observed fishing in the Irish sea.