A drop-off in humpback whale numbers during their annual migration along Western Australia's coast has researchers concerned.
Experts say the trend reflects an overall drop in whale sightings and an increase in strandings across Southern Hemisphere oceans.
A Broome tour operator says there have been a noticeable drop in numbers, with his tours having to travel much further afield to find whales.
Researchers say a drop-off in humpback whales migrating along Western Australia's coast this year reflects a developing trend across the Southern Hemisphere.
Observable whale numbers making the annual journey from the Southern Ocean to WA's northern waters dropped by 60 per cent this year.
Whale researchers and watchers also saw fewer calves and more strandings and entanglements along the state's coastline.
Mothers with calves were also scarce on the southern migration after birthing off the north Kimberley.
"It certainly has been an odd year for the humpback whales," Geographe Marine Research team leader Capri Jolliffe said.
Marine Scientist Olaf Meynecke also described the season as "strange."
"Reports around the Southern Hemisphere, from different populations of humpbacks, are all telling the same story of low numbers," Dr Meynecke said.
The Griffith University researcher said the earlier sea ice melts meant the whales were spending less time in their feeding grounds.
