Dr Dazza: Fishing for Mangrove Jack

Mangrove Jack (Lutjanus argentimaculatus) is a species of fish that many anglers or spearfishers in Moreton Bay aspire to catch, but only a few do so consistently.

Mangrove Jack belong to the family Lutjanidae and other local members of this family of fish include the moses perch, hussar and rosy jobfish.

Mangrove Jack have a large geographic distribution. They are found throughout south-east Asian waters, parts of eastern Africa, Red Sea, Persian Gulf and many Pacific Islands. They range along the entire Queensland coast and much of the NSW coast with occasional stragglers found well south of Sydney.

Juvenile Mangrove Jacks occur in estuaries, and they can extend into freshwater environments. As they grow, they move into offshore waters and can be caught at depths of 120m.

Spawning takes place in offshore waters with larvae and juveniles then moving inshore to rivers and other coastal habitats.

In Queensland, the spawning season of Mangrove Jack is between October and March with a peak during summer.

Mangrove Jack are a highly fecund species and can release up to four million eggs in a single spawning. Successful recruitment is likely to be influenced by rainfall and climate factors.

At least locally, most Mangrove Jacks targeted are juveniles or sub adults.

How big do they get?

Males are generally mature at about 47cm fork length and females at about 53cm fork length. Most females mature at about eight years of age, and males seven although individual animals can mature much earlier.

Their maximum recorded length is just over one metre, and they possibly live for 40 years! A one metre Mangrove Jack would certainly be a fish of a lifetime.

Mangrove Jacks are closely associated with structure and can be found in conjunction with mangroves and fallen timber, rock walls and rock bars, piers and jetties and reef areas.

In many locations, there is much interest in the aquaculture of the species due to its high market value, and in Australia there is also interest in stocking these fish in both marine environments and freshwater impoundments.

In Queensland, the minimum legal size of Mangrove Jack is 35cm and there is an in-possession limit of five fish per person.