Shark nets and drum lines
Shark nets are not made to prevent sharks from entering the beach area. Indeed, sharks have a chance to avoid them as these nets do not form a complete barrier. What nets are designed to do however is to kill resident sharks, as the more often these sharks will enter and leave the beach, the higher the probability that they get entangled in the net. This is merely a culling program.
Shark nets are usually 150 meters wide, 6 meters tall and they are set in 10 meters of water or so. The mesh holes are 50 centimetres wide, which allow small fish to swim over, but kill larger fishes. Sharks which swim into these nets get entangled by their gills. Most die by suffocation.
While it gives the public a false sense of security – up to half of the sharks killed in these nets were on their way out into the wider ocean, this useless and outdated practice negatively impacts marine life. It kills threatened shark species without distinction - completely inoffensive sharks such as grey nurse sharks are particularly vulnerable. Non-targeted species such as dolphins, dugongs, turtles, rays and other fishes are also frequent by-catch victims of these nets.
Drum lines are static baited hooks often added to shark nets to lure targeted sharks and catch them. They are also responsible for by-catch and often blamed for attracting more sharks in beaches where they are set in.
A variety of less expensive, non-lethal alternatives are available, which prevent sharks and other species from being indiscriminately killed. As regards to the little threat sharks represent to humans, educating people to coexist safely with sharks should be the preferred answer to human and shark encounters.