Southern jack study in the frame

THERE wouldn’t be too many fishos who don’t enjoy catching a mangrove jack, and rightly so. Whether you’re casting small minnows into the jade-coloured depths of a tropical snag pile or having heavy leaders shredded along a southern rockwall, jacks offer sportfishing at its challenging best.

Once considered a tropical species, recent years have seen growing awareness that jacks represent a realistic target species for sportfishers in northern NSW. In fact, jack fishing in NSW has a long history, with a few older fishos providing fascinating memories of monumental battles with big “red bream” hooked amongst oyster-encrusted rocks with Ned Kelly poles, wire line and live crabs.

However, many details of the biology and life cycle of southern jacks are unknown. This is in contrast to north Queensland populations, where research has revealed many aspects of their biology, most notably the presence of a distinctive two-phase life history. Almost all jacks residing inshore in northern Australia are immature, with adult fish migrating offshore to take up residence on reefs or around headlands.While it might seem strange to think of a 45cm lure-crunching red devil lurking in a tropical snag as a “juvenile”, it’s generally true!

Whether jacks display a similar life cycle in northern NSW is unclear, as are their spawning habits, growth and diet. To answer these questions, a three-year PhD research project has been funded by the NSW Saltwater Recreational Fishing Trust, and is being jointly undertaken by researchers from Southern Cross University and NSW DPI. Most of the project staff are based at the National Marine Science Centre in Coffs Harbour.

You can help

The project has several components. Beginning this summer, acoustic telemetry will be used to follow the movements of tagged mangrove jack, thereby identifying any offshore movements as well as clarifying seasonal patterns of habitat use within estuaries.

In addition to acoustic tagging, this research requires biological samples, including otoliths (ear bones), reproductive organs and stomach contents. These samples will provide important insights intothe age structure, spawning habits and diets of NSW jacks.

The researchers realise that a lot of keen southern jack fishos carefully release most of their fish, so therefore they’re not being asked to keep a fish that would otherwise be released. However, if you do keep a jack for the table, the frame (filleted skeleton with head and guts intact) will provide valuable information for the project. If you would like to donate a frame, put it in a plastic bag, and keep it cold (freezing is fine), then contact researchers on the details provided below. Everyone who donates a frame will go into a prize draw, which will be handed out towards the end of the project.

To find out more contact Toby Piddocke 0439796609 or (02) 6648 3900; email:

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