Keen observers have encountered sombre sights at the whale nursery in the past two years but now at least one new calf is causing a splash.

A whale calf washed up dead in 2019. Weeks earlier researchers presumed another died after they recorded its mother without her baby. Then came the worrying sign of no females or calves appearing at the nursery at all last year.

Now, Big Coaming - the same whale whose calf washed up dead two years ago - has returned with a new baby in tow.

Mandy Watson, an expert on the region's southern right whales, said the return of a resident female and calf to Logans Beach was fantastic news.

"She is one of our regular breeder females," Ms Watson, an officer at the Department of Environment Land Water and Planning, said.

Researchers are able to track the whales because females typically return to the same breeding ground every three years to give birth, usually between June before then leaving in September or October.

But Ms Watson said Big Coaming had returned to Logans Beach after just two years because losing her earlier calf sped up the whale's breeding cycle.

"We know they can get pregnant straight away and come back two years later. And that is what has happened," she said.

Researchers use each creature's distinct markings including callosities around the head to help identify the whale.

"Their identification patterns are difficult to distinguish when they are young," Ms Watson said.

"We will attempt to identify (Big Coaming's calf) toward the end of the season."

Meanwhile, another whale has given birth to a calf at Narrawong in possibly the first return of southern right whales breeding near Portland since whaling in the region hunted them to near extinction.

"That is a really fantastic sign of recovery, because we haven't really had cow-calf pairs stay at Portland," Ms Watson said.

The whale is thought to be Yanuk Splash, who was named by Narrawong primary school students in 2018.

"Yanuk Splash has a large white blaze," Ms Watson said. "We are pretty confident it is her at this stage."

But back at Logans Beach it isn't all good news, Ms Watson says, with the nursery still expecting two further female calves to arrive - Two Two and Odd Lips.

"Last year we were due for about three or four of our regular females as well and none came so we were hoping they would come this year," she said.

"Occasionally you get one every four years. That is a bit of a trend happening worldwide. That would mean a slower recovery in the population if that trend is continuing."

Ms Watson, the lead author of a new research paper, has found no change in the 2.6 cow-calf pairs that on average have arrived off Warrnambool every year in the past three decades.

Southern right whales gave birth to about 93 calves at Logans Beach - the only established whale calving ground on Australia's south-east coast - between 1980 and 2018.

The southern right whale population that visits the south-east is thought to be about 300 strong. Yet the population is only about one per cent of how many succumbed to whaling, and Ms Watson said researchers feared the mammals were recovering slower than in other regions.

The paper called for a better understanding of juvenile survival, recruitment and female whales' affinity to breeding sites.

However, there are some promising signs this season with whale watchers sighting "socially active" southern rights further east at Bells Beach and Lorne that researchers assume are yet to migrate west.

"It wouldn't surprise me if they would make their way down to Portland. There was a reporting of a sighting in Port Fairy last weekend as well," Ms Watson said.

"We are still waiting for them and they still may arrive."

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