Anglers help with mangrove study

RECREATIONAL anglers are being invited to help Southern Cross University researchers learn more about the habits of the iconic mangrove jack.

PhD student Toby Piddocke from the University's National Marine Science Centre based at Coffs Harbour is using acoustic telemetry to follow the movements of mangrove jack in Northern New South Wales and is offering fishers a gift voucher to the value of $50 for each of the first 20 live specimens donated to the study. (An earlier report saying anglers would be paid $50 per live fish was incorrect).

The research is funded by the NSW Saltwater Recreational Fishing Trust.

At this stage, the research team is seeking live fish from the NSW North Coast locations of Deep Creek (near Valla) and the Clarence River.

"The use of acoustic tags will enable us to track the jacks over a two-year period," Toby said.

"We're particularly interested in seeing whether they move from estuaries to offshore reefs once they reach maturity. As well as that, we're interested in seeing how jacks move around within an estuary. For example, where they spend the day as opposed to the night, and where they go on high tide versus low tide."

Mangrove jack (Lutjanus argentimaculatus) are found in estuaries, coastal swamps and rivers across northern Australia, stretching from Northern NSW into Queensland, the Northern Territory and down to Shark Bay in Western Australia.

Toby said that southern mangrove jack possess some unique characteristics that make them highly prized by recreational anglers.

"In North Queensland estuaries mangrove jack are relatively abundant but their average size is fairly small, around 45 centimetres. However in southern estuaries, between Coffs Harbour and the Queensland border, they tend to be fewer in number but considerably larger, up to about 60 centimetres and three kilograms in weight," he said.

The research will determine whether the size difference might reflect longer inshore residence times by adult fish.

"Not only does the size of mangrove jack in Northern NSW waters make them popular with anglers but they're seen as being really challenging. They're elusive and when you do snare one it puts up a good fight," said Toby.

In addition to the tagging component of the research, mangrove jack frames (filleted skeletons with head and guts intact) are also being sought to study the age, growth, diet and reproduction of the species.

The outcomes of the research will be used to help ensure the long term viability of the recreational mangrove jack fishery in Northern NSW.

Anglers interested in taking part in the research can find out more information by contacting Toby Piddocke at the National Marine Science Centre on 02 6648 3900 or via email mangrovejackresearch@gmail.com



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