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The long-lived Mangrove Jack is classified as sustainable in WA, recovering in the Gulf of Carpentaria and undefined in the NT and East Coast QLD. Stock status is negligible in NSW.

Mangrove Jack are a long lived (> 50 years), late maturing species that can reach a length of over 1 m [Russell et al. 2003]. They are broadly distributed throughout the tropical and sub-tropical Indo-West Pacific [Allen 1985] and exhibit a biphasic life history pattern, where juveniles spend several years in freshwater and estuarine habitats before migrating offshore as they near sexual maturity, and have been reported to a depth of at least 175 m [Pradella et al. 2013].

The distribution of this species within Australian waters extends from approximately Perth, Western Australia, around the north of the continent to Sydney, New South Wales [Pember et al. 2005, Russell et al. 2003]. Genetic analyses indicate that Mangrove Jack consist of a single biological stock across its Australian range [Russell et al. 2003]. This level of mixing is consistent with a life history that involves offshore spawning by adults. However, Mangrove Jack experience moderate to high harvest rates in some Australian fisheries (particularly those targeting adults of this long-lived species), which may cause localised depletion. While juvenile fish have been shown to migrate from freshwater and estuarine habitats to offshore reef environments, often with a movement component of up to 335 km [Russell et al. 2003], once these ontogenetic movements have occurred there have been no reports of adult fish undertaking extensive movements, although studies are limited. As such, limited evidence of adult movement in combination with evidence of varying stock status in different regions indicates that Mangrove Jack likely comprise separate management units.

Here, assessment of stock status is presented at the management unit level―East Coast Queensland and the Gulf of Carpentaria; and at the jurisdictional level―Western Australia, Northern Territory and New South Wales.

Western Australia

Mangrove Jack are landed primarily on the north-west coast of Western Australia as a component of the multispecies Pilbara Demersal Scalefish Fisheries (PDSF: which includes the Pilbara Fish Trawl (Interim) Managed Fishery; the Pilbara Trap Managed Fishery; and the Pilbara Line Fishery) in the Pilbara management region of the North Coast Bioregion; and as a component of the multispecies Northern Demersal Scalefish Managed Fishery (NDSMF) in the Kimberley management region of the North Coast Bioregion of Western Australia [Newman et al. 2020]. Mangrove Jack are assessed on the basis of the status of several indicator species (including, for example, Red Emperor and Goldband Snapper in the Kimberley region) that represent the entire inshore demersal suite of species occurring at depths of 30–250 m [Newman et al. 2018]. The major performance measures for these indicator species are estimates of spawning stock levels. The target level of spawning biomass is 40 per cent of the unfished level, with a threshold reference level of 30 per cent and a limit reference level of 20 per cent of the estimate of initial spawning biomass [DPIRD 2017]. Indicator species assessments using an integrated age structured model determined that the spawning biomass levels of each of the indicator species in the PDSF were either greater than the target level or between the target and the threshold level in 2015 (the year the last integrated assessment was undertaken). The spawning biomass levels of the indicator species were at the threshold level in the NDSMF in 2017 [Newman et al. 2020]. The above evidence indicates that the biomass of this stock is unlikely to be depleted and that recruitment is unlikely to be impaired.

The catch of Mangrove Jack in the PDSF has been low and stable for the past 10 years (2010–19), ranging from 8.9–14.4 tonnes (t), with a mean annual catch of 10.9 t. The catch of Mangrove Jack in the NDSMF has been low and stable for the past 10 years (2010–19), ranging from 0.6–3.4 t, with a mean annual catch of 1.4 t. The above evidence indicates that the current level of fishing mortality is unlikely to cause the stock to become recruitment impaired.

On the basis of the evidence provided above, Mangrove Jack in Western Australia is classified as a sustainable stock.

Mangrove Jack biology [Pember et al. 2005, Piddocke et al. 2015, Russell et al. 2003]

Distribution of reported commercial catch of Mangrove Jack

Western Australia Active Vessels data is unreportable as there were fewer than three vessels operating in Pilbara Fish Trawl Interim Managed Fishery and Pilbara Trap Managed Fishery.

Western Australia – Recreational (Catch) Boat-based recreational catch is from 1 September 2017–31 August 2018. These data are derived from those reported in Ryan et al. [2019]. Shore based catches of Mangrove Jack are not known.

Western Australia – Recreational (management methods) A Recreational Fishing from Boat License is required for the use of a powered boat to fish or to transport catch or fishing gear to or from a land-based fishing location.

Western Australia – Indigenous (management methods) Subject to application of Section 211 of the Native Title Act 1993 (Cth), and the exemption from a requirement to hold a recreational fishing licence, the non-commercial take by Indigenous fishers is covered by the same arrangements as that for recreational fishing.

Northern Territory Recreational Catch from West et al. [2012].

Queensland – Indigenous (management methods) for more information see https://www.daf.qld.gov.au/business-priorities/fisheries/traditional-fishing

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