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They can be sighted at Colac Bay, Riverton Rocks and near Mitchell’s Bay at times.
Southland Surf School coach Jessica Terrill said she had seen about five of the mammals at Colac Bay this summer.
"You often see them travel in small groups."
The dolphins were regular visitors but were more visible to the public during the summer season, she said.
"They love to surf along with us and when you catch waves it’s almost like they are racing you."
Ms Terrill has been a surf coach for about 10 years in the region and said the dolphin numbers appeared to be slowly but surely increasing.
Colac Bay marine researcher Gemma McGrath said two types of dolphins appeared at Riverton and Colac Bay regularly, bottlenose and Hector’s dolphins.
Hector’s dolphins could be identified by their black round-shaped fin and their size, as they were one of the world’s smallest dolphins.
They were native to New Zealand and had a small range along the shoreline, of 30km-50km, which meant they usually remained within their local area.
The Hector’s dolphins at Colac Bay might be different individuals from the ones around the corner at Riverton, Ms McGrath said.
She advised the public when out near the dolphins to behave responsibly.
"Give them their space but enjoy them.
"They are really special, only found in Aotearoa and a lot of the time they are keen to interact."
It was a privilege and honour to be in the same space as the mammals, she said.
"They are quite gentle, inquisitive and friendly."
She had studied the mammals for about 20 years, and had researched the Hector’s dolphins in the region for about three and a-half years.
She had found some Riverton articles dating back to 1922 during her research.
The dolphins were referred to as porpoises until the 1980s, she said.
She hoped to see their numbers increase over the next few years.
"It’s a very slow, precious recovery rate, but we have seen calves every year and we’ve seen them grow up to be little dolphins. So if we could see more of that, that would be great."