The researchers started from the premise that despite rapid growth in marine tourism its impact was not well understood, with most studies focusing only on behavioural changes in sharks resulting from feeding or baiting.

Instead they carried out long-term observations of differences in residency, abundance and behaviour of reef sharks in response to scuba-diving at remote Palmyra Atoll, in the Northern Line Islands between Hawaii and American Samoa in the central Pacific.

Based at a scientific research station there, they used various survey techniques, including remotely operated underwater video cameras carrying small amounts of bait, and acoustic monitoring.

Palmyra is a wildlife refuge where fishing has been banned for 14 years and scientific diving, although intensive, is concentrated entirely on a small number of dive-sites.

While the researchers knew that sharks had previously been shown to change their behaviour towards people in the water over short time-scales, the results of their survey indicated that such changes were likely to be short-lived.

No differences were detected in reef-shark abundance or behaviour between heavily dived and undived locations, and there were no differences in residency patterns at dived and undived sites during a year that saw substantial diving activity, and another year with no diving at all.

“Our results suggest that humans can interact with reef sharks without persistent behavioural impacts, and that well-regulated shark-diving tourism can be accomplished without undermining conservation goals,” concluded lead author Darcy Bradley.

The report, “No Persistent Behavioural Effects of Scuba-Diving on Reef Sharks”, is published in the Marine Ecology Progress Series and can be downloaded here

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