Comments

• Thanks very much for the information. It is wonderful to get an answer to a question that is difficult to phrase correctly. Particularly so, when a few kilometres or decades would have a different outcome.
  We often kayak and occasionally swim in the Brisbane River well above the Mt Crosby Weir. It is an almost pristine environment and it is gratifying to know we share it with platypuses and tortoises rather than bull sharks.
• I've been searching the web for information on Bull sharks and came across a Catalyst program with some information. I do a lot of kayaking on the Brisbane River and was told by an unreliable source that Bull sharks occur between Wivenhoe Dam and Mt Crosby. The source said that he used to swim in the Brisbane River near Fernvale but now only swims in Wivenhoe Dam for fear of being attacked by Bull sharks. The Catalyst program concluded with the following quote when referring to the Brisbane River. "Narration: So next time its a sweltering hot day and the river looks inviting, remember that when you enter the water, whether its fresh or salt, that you are entering the domain of animals that we are only just beginning to understand." I would have thought it unlikely for Bull sharks to ever be found upstream of Mt Crosby. My searching the web indicated that they can swim enormous distances upstream including up rapids. The only time conditions would allow this on the Brisbane River is during a serious flood. If Bull sharks managed to swim upstream in such a flood would they survive in that habitat after the flood was over? If you cannot give a definitive answer an indicative answer would suffice. Regards bandycoot.