Shark nets are submerged and placed around beaches to try to prevent shark attacks on swimmers. They are designed to capture sharks and prevent their escape, until they eventually drown. However they are not thought to be effective, as they need to be placed at a certain level that allows boating and sharks can swim over the top of them.
Sharks are not the only creatures to be captured by the nets, with threatened and endangered species like sea turtles, dugongs, dolphins and whales also being caught up in them. In late 2013 in New South Wales, Australia, a humpback whale calf and a dolphin were both caught and drowned in shark nets.
In New South Wales alone, almost 4,000 sea creatures have been caught in shark nets in the past 20 years (2010 figures). Of the official count of 3,944 creatures, around 60% were sharks and less than 4% of those were considered a target species or harmful to humans. Among them were 15 grey nurses, harmless and considered critically endangered, as well as stingrays (1,269), dolphins (52), turtles (47), whales (6), seals (4), a penguin and a dugong (source: www.smh.com.au).
Shark nets do not physically prevent sharks from reaching beaches. Sharks can and do swim over and around the nets, with research showing some 40% of sharks caught on the beach side of the nets. The risk of being bitten by a shark is less than one in a million in Australia. Regular beach patrols by well-resourced networks of surf life savers are one of the most effective ways of protecting beachgoers from the very small threat sharks may pose. www.marineconservation.org.au
Alternatives have been suggested, such as surf lifesaving patrols, radio signals and sonar technology.
Please read more on the problems with shark nets at www.hsi.org.au