© DEPIThe dead whale washed up on Levy’s Beach on Monday.

A 16-metre-long dead whale has washed up on an isolated beach near Warrnambool, in Victoria's south-west.

The young female fin whale (Balænoptera physalus), which is estimated to weigh 25 tonnes, was found on Levy's Beach on Monday and word leaked out about it amongst local residents on Tuesday.

The Department of Environment and Primary Industries (DEPI) said it did not inform the public sooner as it was planning its overall response, including managing the scene.

DEPI biodiversity officer Mandy Watson said at this stage the cause of the death was unknown.

"These whales are quite vulnerable to ship strike. They are a surface-feeding whale so they are vulnerable from that point of view, and that is one of the bigger threats to the species," she said.

"There's nothing obvious at the moment, but it is washing around in the waves on the shore and it is not easily accessible."

The department said the whale had not been seen in the area before being discovered on the beach.

DEPI was monitoring the whale's position, and planned to move it out of the ocean.

"Being such a long animal and being very heavy, it is estimated to be about 25 tonnes, that is going to present some logistical challenges for us," Ms Watson said.

"DEPI is investigating the possibility of collecting the rare specimen and other options for the carcass."

Fin whales are a vulnerable species that feed mostly on krill, and can be seen in waters off Portland.

"The species is sometimes observed feeding in the Bonney Upwelling which occurs in southern waters off Portland," Ms Watson said.

"Nutrient-rich water flowing up from the ocean floor triggers a bloom in phytoplankton which provides food for a whole range of species including krill."

The department has warned people to stay away from the area, including swimming or surfing at the beach, amid fears the dead whale could increase shark activity.