They have been drum lining / netting over here in QLD for as long as I can remember.
As far as I am aware of there is 1 boat that has a government contract that check the coast from Noosa to Caloundra ( around a 50-60 k's of coastline ) most days, weather permitting.
Most years they are catching between 150 to 300 sharks.
A lot of these are under 2 m long but then they will get some in the 3 to 4 m range also.
When surfing my local the bout will always pull a shark in with the boat in between the line and the beach so surfers and the public can't see what's going on. But you Know.
And when the boat doesn't move for 5 to 10 mins you know they are having trouble getting one of the bigger ones on board.

As with you guys over in WA we see more shark sightings / activity over the warmer months. This is also the same time as the whale season is under coming to a close and young calfs are easy prey.
In recent years it seems that one or two of these whales does get caught, but the guys at seaworld are quick to act and do there best to free any whales caught. ( Can't personally remember the last time a whale was killed from this happening )
This Doesn't kill every shark that is in my local area as I still see and hear of alot of sightings.
From memory any big sharks that die from being caught from being caught are towed out 10 or so k's off shore and cut loose.
I know this is a touchy subject with alot for the idea and also alot against it.
Myself, I know I do feel I little safer knowing this practise is in place over here in QLD.
My 2 cents.