wa shark cull: thousands gather at cottesloe b, page-172

Disco Stu touches on a good point, was about to post something along the same lines
Europeans have been in Oz for about 200 yrs. A blink of the eye relative to how long sharks have been breeding in our waters.
The GW's were considered under threat of becoming endangered and subsequently protected. Any increase in their numbers in the last 20 yrs or so wouldn't come close to restoring their numbers to what they would have been before commercial fishing.