The Moray Firth's population of bottlenose dolphins remains stable, according to a report from Scottish Natural Heritage (SNH).
It is thought the firth and North Sea provide habitat for the world's most northerly resident population - about 200 of the mammals.
More than half of them frequently use the Moray Firth, which is designated a special area of conservation (SAC).
And monitoring indicated an increase in dolphin numbers on the east coast.
The research, commissioned by SNH, was carried out by the University of Aberdeen.
The organisation said the bottlenose dolphin population was still considered to be vulnerable but the results were positive.
SNH marine policy and advice officer Morven Carruthers said: "This is great news for the dolphins and for Scotland in general.
"We have been monitoring dolphins in the Moray Firth SAC for many years and it's been wonderful to see stability in their numbers."