Researchers found an unfortunate side effect to increased tourism to the Ninglaloo Reef region that centers around the native whale shark population; More whale sharks are being injured by the boats that drive the tourism industry.
Whale shark diving is an important part of the Western Australian tourism industry, delivering an estimated at $12.5 million in economic activity for the Ningaloo Reef region. However, almost one-fifth of the whale sharks (Rhincodon typus) in Western Australia’s Ningaloo Reef Marine Park show major scarring or fin amputations.
Emily Lester, a Ph.D. candidate at the University of Western Australia (UWA), and colleagues from AIMS and the Department of Biodiversity, Conservation and Attractions (DBCA), reviewed still and moving images of 913 whale sharks taken by Ningaloo tour boat operators between 2008 and 2013. Of these, 146 or about 16% showed some form of serious injury.
The study, published in the latest issue of Marine Ecology Progress Series, concluded that the distinctive scar patterns strongly suggest many of the injuries are caused by boat collisions.
“Some of the major scars were probably bite marks from predators, but most were the marks of blunt trauma, lacerations or amputations arising from encounters with ships, particularly propellers,” Lester said.
The results of the research show injuries recorded during 2012 and 2013 almost doubled compared to 2011. The data doesn’t include the number of fatal ship collisions, because whale sharks are ‘negatively buoyant’, meaning that when they die they sink to the ocean floor.
“A collision between a large ocean-going vessel and a whale shark wouldn’t be felt by the ship, as a result, it’s likely that we’re underestimating the number of mortalities from ship strike, since our study could only document sharks that survived their injuries,” Lester said.
