A "grey-morph" southern right whale swimming between Port Campbell and Portland has also treated spectators to a rare site, with only a handful known to exist.

The Department of Environment, Land, Water and Planning's Mandy Watson said at Logans Beach two adult southern right whales had paused for a rest at the weekend.

"We are not sure what the sex of those whales is yet. There is no resident females yet in the nursery," Ms Watson said.

She said citizen scientists separately sighted a grey-coloured adult whale.

While calves normally appear lighter in colour researchers have only recorded about six grey adults out of the 400 southern right whales known to frequent the coast.

"They are just born that way," Ms Watson said.

Female whales typically arrive in the Logans Beach nursery in May to June and calve in June and July, Ms Watson said, but this year they've kept researchers and spectators waiting.

"This isn't the first time it has been late. We have had late seasons before, it's probably driven by food, sea temperatures and ocean current current," Ms Watson said.

"We are expecting at least two of our regular females this year that we know of and I think they still will show up except be later than normal.

"Because Logans Beach is a nursery area, the females prefer to be away from the males while raising their calves there. It's the only established nursery in south-east Australia."

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