Blue whales are back, humpbacks thriving in Cape

The biggest creatures on the planet, Antarctic blue whales, are back off Cape Point after being on the edge of extinction.

The critically endangered mammals have been identified in significant numbers through sound recordings.

Marine biologist Fannie Shabangu, affiliated to the University of Pretoria and supervised by whale authority Ken Findlay, said: "We were the first researchers to collect Antarctic blue whale calls off the west coast of South Africa."

The sounds were picked up by hydrophones 200m to 300m below the surface between July 2014 and January this year.

The finding that blue whales abound in South African waters for half the year and another discovery - about unique behaviour by humpback whales off the west coast - were published this year.

Humpbacks were observed for the first time feeding in "super groups" of up to 200 individuals, said Department of Environmental Affairs marine biologist Mduduzi Seakamela.

Last Tuesday, an aerial sighting showed hundreds of humpbacks virtually on top of each other near St Helena Bay about 170km north of Cape Town, said surveyor Meredith Thornton, head of the Dyer Island Conservation Trust.

Seakamela said: "I will never forget October 28 2014, when we first saw about 250 humpbacks feeding off Dassen Island [about 55km north of Cape Town]. The west coast is the only place known on earth where we find these large groups of feeding whales."

Findlay, research chair of oceans economy at the Cape Peninsula University of Technology, said: "This massive concentration of humpbacks, crowded into a space about the size of a rugby field was a novel behaviour not found anywhere else."

Seakamela is now monitoring five tagged humpbacks and is surprised by their behaviour. "We expected them to migrate but only two went to Mozambique. Three of them did not move at all," he said, speculating they could be juveniles not yet ready for mating.

Seakamela left Durban on Wednesday on the research ship SA Agulhas II, which has more than 30 scientists aboard. He is mentoring predator researchers who are recording data during the Indian Ocean voyage.

While humpbacks are thriving off South Africa, this month's aerial survey found that southern right whale numbers are lower than in previous decades.

Els Vermeulen, head of the whale unit at Pretoria University's Mammal Research Institute, said the October helicopter survey covered the coast from Nature's Valley to Lamberts Bay.

She said they counted 183 female southern right whales with calves this year, up from 55 last year. But in 2014 they had seen almost 300 pairs of mothers and calves. Southern rights calve every third year.

Vermeulen said the number of unaccompanied males or non-calving females this year was 161.

"This is a big improvement from last year, when there were only nine, and 2015 when there were 15, " she said. They have counted up to 250 unaccompanied individuals in previous years.

Vermeulen said: "We think the El Niño and climatic changes in the Southern Ocean have affected the right whales." Argentina and Australia had been similarly affected.

Stephanie Plos at Nelson Mandela University said they were studying the impact of the new port in Port Elizabeth on the mother-calf pairs there.

Scientist Simon Elwen, the founding director of Sea Search, said that, overall, whales were doing well off South Africa.

"The exception is the Bryde's whale. There are only a few hundred of them and they need a higher level of protection," said Elwen, who has seen a few in False Bay.