Mangrove Jack (2020)
Date Published: June 2021
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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.
Stock Status Overview
|Northern Territory||Northern Territory||Sustainable||
Spawning stock biomass, fishing mortality
|Northern Territory||Gulf of Carpentaria||Sustainable||
Catch, effort, MSY
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.
Gulf of Carpentaria
Mangrove Jack were exposed to foreign trawling activity between 1950 and 1990 [O'Neill et. al. 2011] with catches being slightly lower than contemporary harvests. During 2002–2011 the Gulf of Carpentaria Developmental Fin Fish Fishery (GOCDFFTF) harvest averaged approximately 50 t which was considered higher than the 30 t MSY identified in a previous assessment [O’Neill et al. 2011]. Since 2012–13, effort has been absent or very low in the GOCDFFTF but has increased to above 40 t in the Northern Territory Demersal Fishery (DF) in 2019. Mangrove Jack in the GOC have been previously considered to be recovering from overfishing due to the MSY being exceeded. The current assessment uses a modified catch-MSY model (developed by Martell and Froese  and modified by Haddon et al. ) and uses data from both Queensland and Northern Territory. The outputs from the model estimated that the 2019 biomass of Mangrove Jack in the GOC was 56 per cent of unfished levels [Saunders and Roelofs 2020] suggesting that the biomass of this stock is unlikely to be depleted and that recruitment is unlikely to be impaired. Similarly, the model estimated that the fishing mortality (0.1) in 2019 was well below the limit point indicating 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, the management unit is classified as a sustainable stock.
Mangrove Jack is a highly regarded fish in the Northern Territory but is one of the less common Lutjanids in this jurisdiction. Almost all Mangrove Jack caught by recreational fishers in the Northern Territory are harvested from estuarine and inshore habitats [West et al. 2012], whereas the majority of the commercial harvest (by the multi-species Timor Reef and Demersal Fisheries) occurs offshore.
The magnitude of the recreational harvest of this species is around 5 per cent of the commercial catch (derived from West et al.  and contemporary commercial catch data). There are no estimates of the Indigenous harvest of Mangrove Jack in the Northern Territory.
The average annual commercial catch of Mangrove Jack in the Northern Territory for the decade spanning 2010–19 was 26 t. An assessment using catch data applied to a modified catch-MSY model (developed by Martell and Froese  and modified by Haddon ), estimated that the 2019 biomass of Mangrove Jack was 54 per cent of unfished levels [Saunders 2020] suggesting that the biomass of this stock is unlikely to be depleted and that recruitment is unlikely to be impaired. Similarly, the model estimated that the fishing mortality (0.08) in 2019 was well below the limit point indicating 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 the Northern Territory is classified as a sustainable stock.
Mangrove Jack biology [Pember et al. 2005, Piddocke et al. 2015, Russell et al. 2003]
|Species||Longevity / Maximum Size||Maturity (50 per cent)|
|Mangrove Jack||57 years, 1 019 mm FL||Male: ≥ 7 years, 450 mm F L Female: ≥ 8 years, 510 mm FL|
Distribution of reported commercial catch of Mangrove Jack
|Hook and Line|
|Hook and Line|
|Hook and Line|
|Recreational||0.9 t (2016)|
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. . 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. .
Queensland – Indigenous (management methods) for more information see https://www.daf.qld.gov.au/business-priorities/fisheries/traditional-fishing
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- Gulf of Carpentaria Mangrove Jack Stock Status Summary - 2020. Unpublished Fishery Report
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- Northern Territory Mangrove Jack Stock Status Summary - 2020. Unpublished Fishery Report
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