Evidence giant blue whale making comeback

In the first multi-year survey at South Georgia Island in the southwest Atlantic where hunting drove whales almost to extinction, an international team of scientists reports some whale populations may be close to full recovery while others show promising signs of a comeback.

University of Auckland whale researcher Dr Emma Carroll, who has co-led the survey with Dr Jen Jackson from the British Antarctic Survey (BAS), says the latest data from South Georgia shows protection of whales has worked.

“South Georgia has a similar latitude to New Zealand’s own sub-Antarctic islands and as with our own populations of southern right whale near the sub-Antarctic Auckland Islands, we knew populations were increasing but these latest results are fantastic,” she says.

“It’s also particularly significant because whales were slaughtered in their tens of thousands at South Georgia and to see them return in such numbers is just an absolute thrill.”

Surveying humpback, blue and southern right whales, the researchers report humpbacks are now a common sight in coastal waters at South Georgia with 790 reported during 21 days of surveying this season.

A preliminary estimate suggests more than 20,000 humpbacks are now feeding there in the summer months before migrating to colder waters in the sub-Antarctic to breed.

The rare and critically endangered blue whale, the largest animal that has ever lived, was sighted just once during the first year of the survey, in 2018. This year blue whales were sighted or acoustically recorded 55 times.

“Continued protection and monitoring is required to see if this unprecedented number of blue whales sightings is a long-term trend, as we see in humpbacks,” Dr Jackson says.

The southern right whale, or Tohorā,  was regularly seen in 2018 but were only rarely seen in 2019 and this season. Dr Jackson says that may be because they preferred to feed elsewhere but the data will be further analysed to better understand feeding behaviour.

Genetic monitoring work pioneered on Tohorā will also be used to understand how southern right whales feeding around South Georgia are connected to wintering grounds around South America.

“What is clear is that protection from whaling has worked with densities of humpbacks in particular similar to those of a century ago and we are thrilled to see them at South Georgia again,” Dr Jackson says.

Full list of science organisations and key collaborators on the survey:
Sea Mammal Research Institute at St Andrews University; the University of Washington; the Woods Hole Oceanographic Institution; Instituto Aqualie, Projecto Baleia Franca; University of St Andrews; Wildscope; Oregon State University; US NOAA; the University of Rio Grande do Norte; the Australian Antarctic Division; Scottish Association of Marine Sciences; University of Barcelona. Key collaborators include the University of Auckland (conducting the genetic work), Instituto Aqualie (collaborating on whale tracking), Woods Hole Oceanographic Institute (studying whale health), the Sea Mammal Research Unit (acoustic analysis and health), the University of Barcelona (analysing the historical catch record), Wildscope (analysing whale abundance) and Happywhale, a citizen science based initiative who publish and share photo-identifications of whales online