Shark Repellent: a new study indicates visual cues could be a deterrent

As a follow up to my post this past Sunday on the Australian government's attempts to control white sharks off the Western Australian coast by a variety of often fatal means, new research has come out regarding another avenue for developing a shark repellent: Eyesight.

According to RedOrbit.com, researchers from Australia have been studying the brains of cartilaginous animals, which includes sharks and rays, and their conclusions point to some species of shark as having a more developed brain than previously thought.

There isn't an implication that the sharks are "smarter" than previously thought, as that often implies intelligence of a sort that we associate with humans.  Rather, while some sharks have developed brains along an evolutionary path that is similar to vertebrates including humans, the sensory abilities of the sharks are perhaps broader in scope and therefore can have an impact on their behavior more than previously suspected.

While chemical shark repellents have focused on confusing or disrupting a shark's sense of smell, the new research poses the idea that visual cues might serve as effective repellents.

“Great white sharks have quite large parts of the brain associated with their visual input, with implications for them being much more receptive to repellents targeting visual markers,” said Kara Yopak, a shark researcher at the University of Western Australia.

And what visual image would a shark possibly find threatening or repelling?

“A shark may recognize a poisonous sea-snake’s markings and swim away, for example, and we can use this information to cue a response.   It’s about understanding how their neurobiology affects their behavior,” Yopak said.  “This information may direct researchers’ efforts towards targeting the visual system when developing repellents for sharks.”

Imagine that the ultimate shark repellent turns out to be a black and white striped banner with the words "This is a giant sea snake.  Go away," emblazoned across the front.  Or perhaps we scuba divers will all start wearing wetsuits with markings that look similar to orcas - a known shark predator.   Anything is worth a try when the alternative is hooking and killing any shark that happens to cruise within the vicinity of a popular beach.

Source: RedOrbit.com

Sharks Win By A Nose: research details stereo olfactory ability

To be the efficient predators and scavengers that they are, sharks have an amazing array of sensory functions - from smell, sight, hearing/vibrations, to sensing electrical impulses. Working in coordination or in a sequence, these capabilities give sharks the edge to survive whether cruising an ocean reef or plying the wide open oceans hundreds of miles offshore.

Now, new research by the Woods Hole Oceanographic Institution (WHOI) and the University of South Florida shows how shark's sense of smell is even more refined than previously thought, by sniffing scents one nostril at a time - a sort of stereo smell-o-vision!

In a recent press release, WHOI researcher Jelle Atema said, “The structure of an odor plume is chaotic and not at all coherent. It’s just like what you see with the Gulf oil spill, which is essentially a gigantic odor plume. The plume breaks up into pieces, floats to different levels and gets transported in a current.”

By determining which nostril detects the odor first, the shark is able to determine a direction, much like our stereo hearing allows us to determine direction based on which ear detects a sound first or with greater intensity. The researchers confirmed this with tests using smooth dogfish, a small shark local to New England waters, and squid odor as an attractant.

But as Atema said, odors are transported rather haphazardly by currents, so sharks bring another sensory ability into play to help steer them in the right direction: the lateral line. This sensitive organ along a shark's body can detect faint vibrations in the water - vibrations like those given off by an injured fish or by the movement of water currents. Previous studies by Atema and fellow colleague Jayne Gardiner of the University of South Florida, showed that sharks use the lateral line to detect the direction of subtle currents - much like sensing wind on the hair of our bodies but with much, much greater sensitivity.

Combining these sensory abilities - stereo olfactory perception and lateral line vibrations - sharks are able to determine a direction and follow an odor to its source. “Inspired by odor, sharks also look for current,” Atema said. “The two together is what makes them so efficient.”

One more reason to look at sharks with awe and fascination and not ignorance or fear.

Read the Woods Hole press release.