Thursday, 9 July 2015

How to protect yourself from a shark: Part 1 and Part 2

July 7, 2015

Dundundundun. Fear of sharks, or more accurately the fear of a shark attack, has terrified people throughout the ages.

A millennia or so ago, there wasn’t much available to protect a swimmer from a shark. A couple of options were essentially just talismans: it was believed either pearls or an actual shark’s tooth, worn as an amulet, would protect a diver. Fortunately now we have an array of methods at our disposal, be they physical, chemical, biochemical, camouflage, or electronic.

1. Barriers

For protection of beach-goers, there are a couple of options. The first is the use of drumlines out in deeper water. A float, usually an empty drum (hence “drumline”) is deployed with a baited hook, while the drum is anchored to the sea floor. Drumlines have been used in Australia and Brazil, where shark attacks have been reduced 97%. Drumlines have an advantage in that they target primarily larger sharks that are more dangerous to humans, like bulls, tigers, and great white sharks.

The second barrier is termed “shark netting.” In use in Hong Kong, South Africa, and Australia, these function as the name implies: a long, floating net is deployed around a beach, and anchored against drift. Designed to stop larger sharks, these nets can still let sharks in, as they often float several meters below the surface to avoid entangling motorboats. That said, in New South Wales Australia, there has only been one fatal attack on netted beaches since the program began in 1937; before the program there was an average of one per year. Nets have been criticized for also catching dolphins and whales, but the use of acoustic “pingers” helps deter these mammals, and the nets are removed during whale migration season.



How to protect yourself from a shark: Part 2
July 8, 2015

Mark Lee Rollins for redOrbit.com – Your Universe Online

A millennia or so ago, there wasn’t much available to protect a swimmer from a shark. A couple of options were essentially just talismans: it was believed either pearls or an actual shark’s tooth, worn as an amulet, would protect a diver. Fortunately now we have an array of methods at our disposal, be they physical, chemical, biochemical, camouflage, or electronic.

In Part 1, we mention a few ways to help prevent a shark attack including barriers and chemicals. Here are a few more ways to stay safe out there:

3. Biological Deterrents

There are several biochemical repellents that have shown promise during initial testing. Dr. Eugenie Clark, an ichthyologist who came to be known as “Shark Lady,” became the first person to discover a natural shark repellent: a milky secretion from the pores of the Moses sole. Dr. Clark described the effect it had as it stopped predatory fish, including sharks. This substance was called pardaxin, a peptide that paralyzes the mouth and gills of anything exposed to it. Unfortunately, paradaxin only remains effective less than 24 hours at room temperature; if frozen, its effectiveness plummets.

Some marine sponges produce compounds that could deter sharks. Extracts of the Caribbean red sponge (containing halitoxin) were dosed to two captive sharks. One shark began “active body thrashing” in 7 seconds, while the second shark “appeared dead” after 20 minutes. However, both sharks recovered. Halitoxin extracts were tested on blue sharks in the wild, stimulated to feed with baits. The lack of deterrence was presumed to be due to the relatively high effective concentration needed in the open ocean.

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