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Signs of premonition in sharks? Sharks in egg cases can detect predators’ fields

A newly release study finds that sharks still encased in egg cases may have the ability to  detect predators’ electric fields, long before they hatch.

Ryan Kempster from the University of Western Australia and colleagues collected and monitored 11 bamboo shark embryo from the Underwater World and Daydream Island Resort aquaria in Queensland, Australia. Researchers were able to discover the shark embryos held the ability to detect electric fields in the lab created to mimic those of predators such as fish.  The team of shark experts said that the study definitively showed the young sharks, even within their egg cases, can sense electric fields that mimic a predator, and respond by reducing respiratory gill movements to avoid detection.

Until now, it remained unclear whether adult sharks, which are known to use highly sensitive receptors to detect electric fields emitted by potential prey, developed the ability to detect potential predators and escape being eaten, or whether it was natural.

“…[S]ome shark (Chiloscyllium punctatum) embryos can detect predator-mimicking electric fields and respond by ceasing their respiratory gill movements,” researchers wrote in a paper published Wednesday in the journal PLoS ONE. “Despite being confined to the small space within the egg case, where they are vulnerable to predators, embryonic sharks are able to recognize dangerous stimuli and react with an innate avoidance response.”

The study is the first to examine whether sharks have the ability to detect the electric fields of predators. Researchers said the study would lead to better shark repellents. Although Kempster noted that he hopes the research will serve an added bonus of raising awareness of the need to protect sharks, which face a growing threat from unsustainable fisheries.

“There are a variety of commercially available, nonlethal electric shark repellents, but the scientific data supporting their effectiveness is limited,” Kempster said in an interview with LiveScience. “As founder of the shark conservation group Support Our Sharks, a driving force behind my work is not only in producing a repellent to protect ocean users from potential attack, but also to protect sharks from being killed.”

According to Kempster, the use of shark repellents in the fishing industry could reduce the number of sharks in catches and possibly lower the number of sharks unnecessarily killed in nets and long lines.

“More research funding should be invested into producing an effective shark repellent. Such devices will also be useful in reducing shark bycatch, by keeping sharks away from fishing gear, to decrease the number of sharks unnecessarily killed each year,” said Kempster.