Thousands of humpback whales have begun their migration from Antarctica to Australia, with a pod appearing in the Sydney harbour on Monday and momentarily halting ferry services.
A group of three to four whales surfaced near Manly Wharf on Monday afternoon, causing the Freshwater ferry service to pause for about five minutes, according to Transport for NSW.
The sighting follows several other appearances in the harbour over the weekend and comes during the annual migration of humpback whales.
The migration sees up to 40,000 humpback whales journeying from the cold feeding grounds of Antarctica to the warmer waters off Queensland and Western Australia to breed and give birth.
The northward migration, often referred to as the “humpback highway,” covers almost 10,000km and is one of the longest migrations of any mammal. The migrating whales tend to swim closer to the shore, making them more visible to onlookers.
“Anywhere you can see the ocean, you have a chance of spotting a whale,” Dr Vanessa Pirotta, a marine scientist, told The Guardian, adding that peak migration season was “pretty much like whale peak hour” along Australia’s east coast.
Researchers are now seeing changes in the humpback migration pattern, however. A recent study, published in Frontiers in Marine Science, notes humpback calves being born much further south than expected, including off the Tasmania coast and New Zealand’s South Island, which are not traditionally considered calving grounds. They say the shift may be linked to the waters getting warmer due to rising ocean temperatures.
Although the humpbacks continue to recover from near-extinction due to commercial whaling, with latest estimates of their population ranging from 30,000 to 50,000, conservationists say the species remains vulnerable to human impact, especially during the migration season.
Entanglement in fishing gear is one of the biggest threats. In an effort to reduce such risks, OceanWatch Australia and similar groups are running initiatives like the East Coast Whale Entanglement Mitigation Programme, which is trialling modified gear designs.
The humpback migration typically peaks in June and July but is expected to continue through to October, with the whales returning south with newborn calves. Scientists say this year’s observations will be key to understanding how these iconic mammals are adapting to a warming ocean.
