A new study by Macquarie University published this week in Marine and Freshwater Research has revealed Port Jackson sharks undergo yearly migrations from their breeding site in Jervis Bay, out to Bass Straight and back – a round trip of 1200km.
An iconic species in Australia, Pork Jackson sharks are arguably the most common shark species in coastal waters of southern Australia, however we know relatively little about them.
The team of Macquarie researchers has been studying their behaviour for the past five years and have been surprised by the results.
“When people think of Port Jackson sharks they often think they are kind of a lazy species,” said Associate Professor and group leader Culum Brown.
“They spend most of their day lying around not doing much. But when we started receiving tag detections from receiver stations near Cape Barron Island – over 600kms away – we realised this reputation is unfounded.”
The study, funded by Sea World Research and Rescue Foundation, Australian Research Council and Taronga Zoo, shows the majority of the acoustically-tagged sharks migrated south and were detected by listening stations along the Australian coastline.
“These sharks have a very long life and the tags have enabled the researchers to follow individuals for up to 10 years,” he said.
Post doctoral researcher Johann Mourier explains the group now has five years’ worth of data on some of these sharks and have found they make the same migration year after year.
“The fact they come back to exactly the same place is interesting. How do they know where they are going?”
One of the advantages of acoustic tracking technology is the ability to closely monitor the behaviour of sharks that are all but invisible from the surface.
“The level of detail is fantastic,” said Brown.
For instance, the group was able to show that the migration speed of males is faster than females and the sharks move faster when travelling south than when travelling north.
“So, it looks like these sharks are hitching a ride on the East Australian Current – just as Marlin and Dory did in Finding Nemo,” he said.
Jo Day from Taronga Zoo explains that a string of receivers across the entrance to Jervis Bay pin point exactly when sharks come and go.
“The information we gather from this shows that males arrive early, establish themselves on their home reef and patrol, hoping to intercept females that arrive a few weeks later. Males also depart early and leave the females in peace to lay their eggs which hatch about 10 months later.”
Like many sharks, Port Jackson sharks are long lived, are slow growing and have a low reproductive output. This makes them highly vulnerable to fishing related pressure. The International Union Conservation of Nature states that sharks are among the most at risk group of animals on the planet. Only around a quarter of the approximately 1000 shark and ray species are considered safe from extinction.
“Research like ours provides key information about sharks and their behaviour. The information can be directly used to better manage species either for sustainable fisheries or conservation,” said Brown.
“We can’t possibly hope to manage sharks if we haven’t the faintest idea what they are doing and where they go.”
Bass, Nathan Charles, Mourier, Johann, Knott, Nathan A., Day, Joanna, Brown, Culum, and Guttridge, Tristan (2016). Long-term migration patterns and bisexual philopatry in a benthic shark species. Marine and Freshwater Research. http://dx.doi.org/10.1071/MF16122
An iconic species in Australia, Pork Jackson sharks are arguably the most common shark species in coastal waters of southern Australia, however we know relatively little about them.
The team of Macquarie researchers has been studying their behaviour for the past five years and have been surprised by the results.
“When people think of Port Jackson sharks they often think they are kind of a lazy species,” said Associate Professor and group leader Culum Brown.
“They spend most of their day lying around not doing much. But when we started receiving tag detections from receiver stations near Cape Barron Island – over 600kms away – we realised this reputation is unfounded.”
The study, funded by Sea World Research and Rescue Foundation, Australian Research Council and Taronga Zoo, shows the majority of the acoustically-tagged sharks migrated south and were detected by listening stations along the Australian coastline.
“These sharks have a very long life and the tags have enabled the researchers to follow individuals for up to 10 years,” he said.
Post doctoral researcher Johann Mourier explains the group now has five years’ worth of data on some of these sharks and have found they make the same migration year after year.
“The fact they come back to exactly the same place is interesting. How do they know where they are going?”
One of the advantages of acoustic tracking technology is the ability to closely monitor the behaviour of sharks that are all but invisible from the surface.
“The level of detail is fantastic,” said Brown.
For instance, the group was able to show that the migration speed of males is faster than females and the sharks move faster when travelling south than when travelling north.
“So, it looks like these sharks are hitching a ride on the East Australian Current – just as Marlin and Dory did in Finding Nemo,” he said.
Jo Day from Taronga Zoo explains that a string of receivers across the entrance to Jervis Bay pin point exactly when sharks come and go.
“The information we gather from this shows that males arrive early, establish themselves on their home reef and patrol, hoping to intercept females that arrive a few weeks later. Males also depart early and leave the females in peace to lay their eggs which hatch about 10 months later.”
Like many sharks, Port Jackson sharks are long lived, are slow growing and have a low reproductive output. This makes them highly vulnerable to fishing related pressure. The International Union Conservation of Nature states that sharks are among the most at risk group of animals on the planet. Only around a quarter of the approximately 1000 shark and ray species are considered safe from extinction.
“Research like ours provides key information about sharks and their behaviour. The information can be directly used to better manage species either for sustainable fisheries or conservation,” said Brown.
“We can’t possibly hope to manage sharks if we haven’t the faintest idea what they are doing and where they go.”
Bass, Nathan Charles, Mourier, Johann, Knott, Nathan A., Day, Joanna, Brown, Culum, and Guttridge, Tristan (2016). Long-term migration patterns and bisexual philopatry in a benthic shark species. Marine and Freshwater Research. http://dx.doi.org/10.1071/MF16122
