Injuries to Ningaloo’s whale sharks are increasing. The cause? Likely boat collisions

By AG STAFF 24 January 2020
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It’s estimated that one fifth of the whale shark population in Ningaloo have some form of serious injury.

A “SHARP INCREASE” in injuries to Ningaloo whale sharks, possibly due to vessel collisions, has been identified in new research by the Australian Institute of Marine Science.

In 2016, the world’s biggest fish had its conservation status updated from vulnerable to endangered on the IUCN Red List, and now, this recent data lands yet another blow.

Scientists analysed images of 913 whale sharks between 2008 and 2013, and found one fifth of Ningaloo’s whale sharks had some form of serious injury.

“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,” says AIMS marine biologist Emily Lester.

The difficulty, however, is identifying where exactly the collisions may have taken place, as whales sharks are known to travel thousands of kilometres beyond the Ningaloo Marine Park.

The researchers are eager to understand why injuries doubled in 2012 and 2013 compared to 2011. 

“One possible explanation is that there is an increase in shipping activity throughout the whale sharks’ range – inside Ningaloo and out – and collisions are becoming more frequent,” says Emily. 

It’s also possible that the data regarding the increase in injuries is conservative. The paper notes, “sharks are negatively buoyant, which means that the bodies of animals killed or incapacitated by ship strike will sink and because the carcasses are not recovered, the mortalities are often unreported or undocumented”.

Collision between Ningaloo’s whale sharks and vessels isn’t a new issue. They’ve been documented since the early 20th century. 

According to co-author of the paper Holly Raudino, the first steps to aiding the issue will be “identifying hotspots of where these collisions are occurring through spatial modelling”.