Well we all know that the Bull shark (Carcharhinus leucas) inhabit the bays and waters around Queensland. One of the other projects I have is looking into their movement,
First lets understand something, bull sharks are cool, like most sharks, they have been in these waters far longer then we have been. They are also often confused with the lesser known, Pigeye shark, which looks identical:
They have been there before you had your house on the river, or took your dog for a swim and they have been there before you read the news papers of listened to the news tell you that some one caught a bull shark near a popular swimming place. Nothing has changed. There were no shark - human interactions then and there are still very low numbers of interactions for the amount of people in the water per day. Awesome.
Bull sharks are considered the most dangerous shark in the water, not because of its jaw strength or its size (maximum 3 m total length) but because of its home habitat that is shared with humans! Just because we live here and moved into there home, they are considered extremely dangerous due to the probability of encounter, which is still low.
Basically they are born in brackish (lower saline waters) of estuaries and rivers at around 50 - 80 cm, they are the only shark than can tolerate fresher waters. the adults then leave that system for their normal coastal habitat. Yes most shark lay their pups in areas that are not suited for the adults, since sharks eat sharks and their own species, this is advantageous. The pup remains in these areas, moving around and growing. As it grows, it travels closer to bay waters and when mature, they enter the coast waters offshore and can travel large distances. This is already known and public knowledge. This also means they are found around river openings and bar crossing, places were surfers like to surf at headlands. Great. In clear waters that is not an issue.
A recent paper was published in the scientific literature that shows the main driving factors for bull sharks is rain! Yes, this makes sense since they like that fresher water. Under heavy rain where fresh water flows out of the rivers, bull sharks swim around the coastal openings and up the rivers and bays, I should also mention that they water is also murky during rain events. So a human cannot see it these waters, and guess what? neither can a shark. But they have impressive adaptation to aquatic life, they can feel electric impulses, pressure, smell and hear things very well, though this doesn't afford them the ability to determine what that something is. They, like us, still need to investigate and, like us, touch things! I never would have guessed they don't have hands, what they do have is sensitive teeth. No we all can guess to what happens there, it touches you, you can't see it and this react but pulling away and bugger, that hurt. luckily these interactions are still low and they tend to keep away from large thrashing objects. I don't know why you are in that type of dirty and murky water for anyway, so you can only blame yourself.
This information is great and can be used to be shark smart when you enter the water is awful conditions and wonder why no one else is in there with you.
In my years of catching these sharks, I have never feared them or had a problem with them. They are not super aggressive seem to have the will to jump out of the water and bite people. They are calm, collective and literally just doing what they do.
Part of our bull shark movement project is tagging and tracking them to gain further knowledge in to their life-cycles. I have learned a lot since working with them and I look forward to the information we gather from these studies.
Cheers
Johan