Push to Ban Sharks

[Neferti]

Many years ago my husband and I, plus friends, used to scuba dive ... saw a few sharks but it never bothered me while under water. Everything underwater looks huge!


What really worried me was when sailing on the Sydney Harbour and seeing shark "fins" and then human turds ...... the turds disgusted me more than the shark fins.

[Outlaw Yogi]

Apparently yes, according to both divers and surfers who've tested it.

I question the rigour of this testing. This sounds like a snake oil tiger repellent.

Tests I saw showed sharks moving in close, then quickly darting away once the stripes/bands became visible.

If these are the same tests I saw, they were performed under water, not on the surface, and the shark behaved exactly the same with the unstriped control.

Colours apparently make quite a difference too. Bright colours like red, orange, yellow seem to be targeted, where as green and blue seems to be ignored.

....

[Edit: even these photos are misleading because the shark won't see colour.

Tests imply otherwise.

Despite plenty of ill informed websites stating the opposite, early vertebrate neurobiologists in Western Australia have shown that sharks are biologically unable to see colour. However, this is not inconsistent with sharks being unable to distinguish some colours, like green and blue, from their backgrounds.

There's also electric shark repllant - small pulses from a battery - which according to rumour works quite well too.

While sharks do have electro receptors and can therefore sense these fields, the part of their brain which processes this information is relatively small, while the visual and olfactory centres are much larger. This suggests a visual or olfactory repellant would be much more effective than the electric repellant, and that a shark would likely ignore a repellant where a more poweful visual hunting cue exists.

It is believed all black wetsuits resemble seals and surfboard + surfer silhouettes resemble turtles, but it's still speculation.

Which would be a very strong visual hunting cue. And the colour of the wetsuit would make no difference when hidden above a board to a hunter striking from below. But as you say this is speculation and rumour.

So much of what you read, and what you have said is speculation. While some may be true, I hope you will support funding some real experts to scientifically evaluate them before relying on the repellents.

The first tests I saw were on colour, and bright colours were clearly targeted more.
The banded wetsuit was tested underwater by divers (forget where) and on the surface by surfers in South Africa [white pointers]. The reaction of the sharks was obvious.
According to this article US navy found similar results regarding colour, despite colour blindness.
http://www.abc.net.au/am/content/2011/s3116088.htm

[freediver]

I can't pick out a lot of colours underwater either. It is mostly just green on green. Piscivours don't really need colour vision. It is mostly bright white food vs dark background anyway. I would expect a big difference with sharks that hunt seals and turtles.