Monday, 28 May 2012

Triadic sensory approach suggested to deter shark attacks

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Shark attack“It may not be possible to repel sharks by only interfering with one sense such as electroreception.”—Prof Collin. Image: Herman YungRESEARCHERS at UWA Oceans Institute are now closer to understanding the how and why of shark attack and, more importantly, how to prevent them.

There have been four fatalities from sharks in WA in the last twelve months. The sensory cues and behaviour behind such attacks has remained unclear, but highlighting the latest research on how sharks sense their world is revealing a complex sensory system.

Winthrop Professor Shaun Collin who led the study says, “The work shows that there is a high level of variability between species”.

“A clear message is that each species is adapted for a particular habitat and the sensory cues they react to in the wild are also different.” 

The relative importance of the senses varied greatly across shark species and is tightly linked to lifestyle, feeding behaviour and habitat.

The team reviewed the current state of knowledge of three areas of sensory research in sharks; vision, their electro-sensory system, and their neurobiology.

Prof Collin says one of the biggest surprises revealed by the study is that sharks appear to be colour blind unlike their close relatives stingrays and elephant sharks, which have trichromatic vision.

“Contrast, rather than colour, may be an important cue for sharks that use vision to hunt for food.” 

This has implications for those wearing dark wetsuits, viewed by sharks against a bright sky from below.

Current shark repellents target the shark’s unique and powerful electroreception abilities.

Although important for sharks in detecting prey at close range Prof Collin says smell remains extremely important in detecting odours over long distances.

Equally, sound is thought to be of prime importance in prey detection and early research suggests it is an important sensory cue.

UWA has an extensive research program on the senses of shark’s and other cartilaginous fish.

“By looking at multiple species we can gain a better understanding of the relative importance of each sense and how the information is processed by the central nervous system” he says.

Such work will lead to better understanding of shark behaviour in the wild.

The results indicate the need to target a variety of shark senses at a range of thresholds, rather than a blanket repellent against shark attack.

“It may not be possible to repel sharks by only interfering with one sense such as electroreception.” Prof Collin says.

The research appeared in the April issue of the 'Journal of Fish Biology', a special issue detailing the current status of elasmobranchs (sharks and their relatives) and their conservation.

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