The Dangers of Shark Nets | When Sharks Attack

For the past 20 years, New South Wales averaged four shark attacks a year. But in 2009, a staggering 17 attacks occurred, with species ranging from white sharks to wobble gong sharks. With such a variety of species behind the spike, investigators focused on something that affects them all. Marine biologist Holly Richmond heads out to investigate.

She dives in to get a closer look at shark nets, first deployed in 1937. They're at more than 50 public beaches across New South Wales, typically around 200 yards offshore. These meshings form an underwater fence with a simple purpose. Basically, shark nets are a culling device, so their aim is to catch and kill sharks.

Supporters of the program believe that they've helped keep sharks away from innocent beachgoers. But critics contend there's a harmful downside. Putting a net in the ocean, you're going to catch a variety of different animals: rays, dolphins, whales, sea turtles. There have been dugongs up north. There's a variety of different animals. Pretty much anything that's in the ocean is going to get entangled in these nets, and all this bycatch could have an unintended side effect tied to one of a shark's most important senses.

Shark expert Dr. Vick Petamores cuts in to get a look. "The brain is really the center point for all the different senses, so that it can detect food and other animals in the environment. If there's bycatch stuck in a net, a shark will use two of its senses. Sharks have got a really, really good sense of smell, and it allows them a really acute ability to detect fish blood and unusual smells in the water. Additionally, sharks use their lateral line system to detect the prey item moving in the water. So bycatch could, in fact, draw sharks closer to the nets that are intended to keep them away."

In 2009, reports emerged that holes had formed in shark nets similar to those deployed in New South Wales. Could sharks, drawn in by bycatch, be slipping through flawed nets and coming into contact with humans? [Music] [Music] You.