Their migration is synced with the peak of an eastward-flowing current, triggering the huge schools to spawn en masse.
As the eggs are released, the current will carry the next generation to protected coastal nurseries in the east.
An annual event to extend the fish's bloodlines, and a potential feast for others.
Gray nurse and copper sharks, more than three meters long, they are heading straight for the migrators.
But the Australian salmon are no easy targets, even for sharks.
When one fish senses its neighbor getting too close, it speeds up.
The whole school, moving as one.
