Something is happening with the southern right whale population, scientists say
Australia's southern right whale population growth has stalled, raising questions about the recovery of a species that was nearly driven to extinction by historical whaling, according to a new study.
Southern right whales are large migratory baleen whales that can be spotted off the Australian coastline in winter as they travel north.
The whales come close to shore, which made them ideal, or "right", for whaling in the 1800s.
"Around the early 1900s, there were so few individuals left that certainly around Australia and New Zealand they were considered extinct," Institute for Marine and Antarctic Studies postgraduate researcher Anne Grundlehner said.
Only a few hundred remained worldwide when whaling the species was banned.
The researchers found the annual abundance of calves showed strong growth from 1976 until at least 2010, but began to stagnate around 2016-2017.
(
Supplied: Joshua Smith
)
The Australian population has experienced significant growth since the late 1970s, with very rough population estimates now around 2,000-3,500.
But a new study by researchers from the Institute for Marine and Antarctic Science (IMAS), the University of Tasmania and the Australian Antarctic Division has found their population recovery seems to have recently stalled at a level far below pre-whaling levels, and questions whether it might be the "end of an era for southern right whale recovery".
The study, published in the journal Global Change Biology, analysed aerial survey data from 2,000 kilometres of coastline between Augusta in Western Australia and Ceduna in South Australia, collected between 1976 and 2024.
The researchers found the annual abundance of calves showed strong growth from 1976 until at least 2010.
But they found annual births began to stagnate around 2016-2017.
"We were very concerned to find not only slowed growth in births in this population, but an actual halt and what looks like the onset of a decline," Dr Grundlehner, the report's lead author
said.
She said the population's current size was estimated to be about 16 per cent of its pre-whaling abundance.
"But likely even less, as this is a pragmatic estimate because there is much uncertainty around pre-whaling levels.
"The fact that the growth in annual births has halted, while the population size is well below pre-whaling abundance, is a pretty big finding.
"
We are very certain that the southern right whale abundance around Australia is by far not what it used to be.
"
Industrial whaling decimated the population of a number of whale species throughout the 1800s.
(
Offshore whaling with the Aladdin and Jane, painting by William Duke, 1849
)
The causes behind the stalling population growth is not clear.
"We really need to study all the potential drivers, one by one, to understand their effects on right whales' survival and reproduction, and see if we can find any relationship between potential drivers and the species births and the worrying trends we found in their abundance around Australia," Dr Grundlehner said.
"Because this species is considered endangered in Australian waters, understanding the causes behind the stalling population growth will be critical to inform appropriate conservation actions," IMAS researcher and co-author associate professor Stuart Corney said.
"
The Southern Ocean ecosystem must have substantially changed in response to the large-scale removal of whales in the past.
"
Dr Grundlehner said climate change and other human pressures on marine environments could also be playing a role.
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