Study suggesting sharks are color-blind could help prevent attacks
Using a technique called micro-spectrophotometry -- which measured the light-sensitive cells in the eyes -- the joint study, conducted by researchers from the University of Western Australia and the University of Queensland, looked at the potential for color vision in numerous shark species caught off Queensland and Western Australia and concluded that they have only one type of cone photoreceptor in the retina.
"Humans have three cone types that are sensitive to blue, green and red light, respectively, and by comparing signals from the different cone types we get the sensation of color vision," Nathan Hart, associate research professor at the University of Western Australia, said in a news release. "However, we found that sharks have only a single cone type and by conventional reckoning this means that they don't have color vision."
"It has long been assumed that sharks have some sort of color vision and indeed have a preference for certain colors," Hart said.
"The term 'yum, yum yellow' was coined when it was discovered, in tests by the U.S. Navy, that some species of shark were attracted more to yellow than to other colors; this was of concern as the Navy wanted to supply its sailors with yellow life vests that would be more visible in rescue situations.
"Our study shows that contrast against the background, rather than color per se, may be more important for object detection by sharks," Hart said. "Now we know a bit more about how such sharks see the world, it may be possible to design swimming attire and surf craft that have a lower visual contrast to sharks and, therefore, are less 'attractive' to them. After all, most shark attacks are thought to be the result of curiosity on the part of a shark that has been attracted to an unusual stimulus, rather than some premeditated ambush."
Hart said that the discovery may also assist in the development of fishing gear that could reduce accidental catches of sharks by long-line trawlers.
"This may help us to design long-line fishing lures that are less attractive to sharks -- whilst still effective for the target fish species -- and thus help to reduce the massive by-catch of sharks in this industry," he said.
-- Kelly Burgess
Photo: Researchers have found that sharks, like this white shark, may be color-blind. Credit: Christy Fisher / Sharkdiver.com