People have sighted whales temporarily at Logans Beach, and whale calves on the Victorian coast generally, but so far no female whales have stayed in the nursery.

The southern right whales are usually born off Warrnambool in June and leave in September and October.

Department of Environment Land Water and Planning Natural Environment Program Officer Mandy Watson said whales had "fidelity" to certain calving grounds that they visited every three years.

Researchers had been expecting females that calved at the nursery in 2017 to arrive off Warrnambool this year.

"But we haven't seen them," Ms Watson said.

"We expected to see some of our regular favourites like Big Lips and Long Coaming.

"We would assume they just haven't migrated this year, which means they weren't going to calve for some reason."

She said it was a worrying sign for the critically endangered species.

"If we are seeing extended calving intervals, that's going to slow population growth and that is concerning for a very small and genetically distinct population that has not recovered from whaling," Ms Watson said.

But she said the jury was still out on why the cow-calf pairs had not arrived yet this year.

"There has been talk around the impact of climate on food availability and that can affect breeding," Ms Watson said.

"These whales migrate down to sub-Antarctic regions for feeding and we don't understand what the impact is from climate on those food resources, all is speculation at this stage."

Ms Watson said an emerging calving ground at Encounter Bay in SA had recorded three calves this season while the Head of the Bight, the largest calving area in Australian, had fewer calves than usual.

"We have had years where we haven't had any whales at Logans Beach, it's not unheard of, but there are definitely females we expected this year that haven't arrived," she said.

Five whales with calves were seen at Logans Beach in 2019, but two calves died, another worrying sign for researchers.

"That is very concerning and we've never recorded it before," Ms Watson said.

Ms Watson said stay-at-home coronavirus orders had also reduced data she received from citizen scientists, slowing the identifying and tracing of whale movements along the coast.

"There is still time for our females to arrive with their calves. Perhaps they have been caught short and calved elsewhere along the Victorian coast this year, but time is running out for this season," she said.

Have you signed up to The Standard's daily newsletter and breaking news emails? You can register below and make sure you are up to date with everything that's happening in the south-west.