It’s not just swimmers, surfers and fishers making the most of the warm weather – bull sharks are also active and on the move, according to University of the Sunshine Coast researchers.
Dr Bonnie Holmes is leading a long-term program mapping the movement, ecology and genetics of the Sunshine Coast’s bull shark population to inform better management efforts and safer interactions with humans.
The project has been nominated as a finalist in the Noosa Biosphere Awards.
After two years of tagging and tracking sharks from Noosa to Moreton Bay, Dr Holmes said some clear patterns were emerging in the sharks’ behaviour.
“The data shows bull sharks on the Sunshine Coast are most active in the summer months – especially when the water is murky after rain. They are least active during the day, near the river mouths, when conditions were clear,” Dr Holmes said.
“We’ve tagged 75 individuals across the Noosa River, Maroochy River and Pumicestone Passage systems but despite spending the same amount of time in the Mooloolah River, we’ve only managed to tag one bull shark there to date.
“We suspect changes to the natural entrance of the Mooloolah – increased urbanisation, construction and the corresponding removal of mangroves (fish habitat) – has caused a reduction in numbers in that system.”
The study found that even as Sunshine Coast bull sharks began to explore coastal waters in their teenage years and into adulthood, they remained very attached to the local river systems they were born in.
Dr Holmes said it’s provided fascinating insights into the connecting role the species plays between our local river systems.
“We tagged a female in 2018 named ‘Betty-Sue’ during a pilot study and despite her range extending from Moreton Bay to Rainbow Beach, she consistently comes back to one or two favourite spots in these local systems, all these years later.”
It is hoped the data can not only fill gaps in our knowledge about the species, but help inform and improve practices that facilitate safe shared use of the waterways.
“Shark activity in South East Queensland starts picking up around this time of year, and we urge everyone to visit the DPI SharkSmart pages for information and practical steps on how to reduce your risk of interaction,” Dr Holmes said.
“Thankfully, for the most part, we already successfully share these waterways with a healthy population of local bull sharks. A large number of juveniles and sub-adults live in the lower reaches of the river estuaries from Noosa down to Golden Beach – but there’s been no reported interactions in recent history despite lots of human use.
“We always urge practicing caution in these areas. But they’re a good sign of a healthy ecosystem,” Dr Holmes said.
