DEC senior wildlife officer Doug Cochran said he believed the 4m whale shark, which found its way into Cockburn Sound on the morning of April 18, was filter-feeding in the area.
While the slow-moving sharks have rarely been found as far south as Hamelin Bay and around Rottnest Island, this was the first report he knew of in Cockburn Sound.
The reason? While it’s possible he/she just got lost, it looks like global warming is the culprit.
‘The ocean has been warming over the past couple of years and that brings species down from the north,’ Mr Cochran said.
‘Cockburn Sound is an interesting place, it’s rich in a number of species.
‘In fact, over the years we’ve had pygmy right whales, minke whales and some of the other transitory whales feeding there, even killer whales have been sighted on the other side of Garden Island.’
Mr Cochran said Cockburn Sound also provided ample food for some species and was regularly used by mother dolphins for calving.
Whale sharks can grow up to 12m and specimens of 8m long are seen routinely. They give birth to hundreds of live young in the waters of Indonesia and Thailand.
‘There’s not a lot known about them,’ Mr Cochran said.
He said it was unlikely the animal had become stranded in the sound due to sickness because unlike blubber-filled whales, sharks had a swim bladder and tended to sink to the bottom when dying.
‘It’s at the surface, so that typically looks like he was filter-feeding,’ Mr Cochran said.
‘This is probably a one-off.’
Species such as Penguin Island’s famous little penguins are suffering the impacts of warming coastal waters.
Mr Cochran said the warming waters were providing an interesting time for marine scientists.
‘Some species may not be able to tolerate it and some will thrive,’ he said.