*

Of the nine Barramundi stocks across WA, the NT and QLD targeted by commercial fishers, seven are sustainable. The Princess Charlotte Bay stock is undefined as it no longer has catch and effort indicators due to management changes. The South-East Coast stock at the species' cool-water range limits in southern QLD is undefined.

Barramundi (Lates calcarifer) are a large, predatory fish distributed across most of the Indo-West Pacific region, from the Arabian Gulf to China, Taiwan, Papua New Guinea and northern Australia [FAO 2020]. They are protandrous hermaphrodites (maturing as males first, then changing sex to female; Moore [1979]) that exhibit individual variation in habitat utilisation/migratory patterns during their life history [Crook et al. 2016]. The productivity of Barramundi populations is closely linked to variation in rainfall, with wetter years linked to enhanced juvenile growth, recruitment, and fishery productivity [Staunton-Smith et al. 2004; Robins et al. 2005; Halliday et al. 2010; Leahy and Robins 2021; Crook et al. 2022].

The genetic stock structure of Barramundi in Australia is complex. Keenan [1994] described 16 subpopulations of this species (through allozyme analyses) across most of its Australian range, with each subpopulation encompassing an individual catchment, or several adjacent catchments. More recently, Jerry et al. [2013] and Loughnan et al. [2019] described 21 distinct subpopulations (through microsatellite analyses) from samples collected over a wider geographic range than that of Keenan [1994]; noting that both recent works were based on the same set of tissue samples, many of which were initially collated by Keenan [1994].  

Difficulties in obtaining relevant biological and catch-and-effort information from each biological stock in Western Australia and the Northern Territory precludes individual assessments of these stocks. Therefore, the assessments for these jurisdictions were undertaken at the level of the management unit (Kimberley Gillnet and Barramundi Managed Fishery, Western Australia; and Barramundi Fishery, Northern Territory). For Queensland, six biological stocks described by Keenan [1994] [Fisheries Queensland 2010] with an additional seventh stock of ‘vagrant’ fish, that venture south of 26⁰ South have been assessed. An eighth stock of Barramundi was identified in Queensland in more recent studies [Jerry et al. 2013; Loughnan et al. 2019], however tag-recapture information indicates that the boundaries of these subpopulations are somewhat porous, with individual fish moving between subpopulations [Infofish Australia 2014, 2020]). Additionally, there are practical limits on the number of assessments that can be undertaken on this species. The seven biological stocks assessed in Queensland are: Southern Gulf of Carpentaria, Northern Gulf of Carpentaria, Princess Charlotte Bay, North-East Coast, Mackay, Central East Coast and South-East Coast.

Here, assessment of stock status is presented at the management unit level—Kimberley Gillnet and Barramundi Managed Fishery (Western Australia), Barramundi Fishery (Northern Territory); and the biological stock level—Southern Gulf of Carpentaria, Northern Gulf of Carpentaria, Princess Charlotte Bay, North-East Coast, Mackay, Central East Coast and South-East Coast (Queensland).

Northern Territory

The most recent assessment of the Barramundi Fishery (Northern Territory) management unit (using data to the conclusion of 2019) indicated that this stock was impacted by high fishing pressure in the late 1970s and early 1980s, falling to 36% of the unfished (1950) biomass [Grubert et al. unpublished]. However, there has been a strong recovery since that time, with the annual biomass as a proportion of virgin biomass exceeding 60% for the last two decades, reaching 88% by the end of 2019. Commercial effort has declined substantially during the last decade due to a range of operational challenges (e.g., declining profitability, the loss of access to fishing gounds, the Covid-19 pandemic). At the time of the most recent (2019) assessment, annual commercial catch was 276 t, having declined from 736 t in 2012. Since that time, commercial catch has declined further to historic lows of 176 t in 2022.

Monitored stocks have a broad length and age distribution, with little sign of a reduction in the proportion of older age classes [NTG 2018]. The above evidence indicates that the biomass of the stock is unlikely to be depleted and that recruitment is unlikely to be impaired.

The contemporary (2019) fishing mortality rate, as a proportion of fishing mortality at maximum sustainable yield (MSY), was estimated at 19%, roughly one fifth of the rate required to achieve MSY [Grubert et al. unpublished]. Recaptures from tagging programs also suggest that the annual harvest rate for all sectors combined is consistently below five per cent. The above evidence indicates that the current level of fishing pressure is unlikely to cause the stock to become recruitment impaired.

On the basis of the evidence provided above, the Barramundi Fishery (Northern Territory) management unit is classified as a sustainable stock.

Barramundi biology [Davis 1982; Roberts et al. 2021; Budd et al. 2022]

Distribution of reported commercial catch of Barramundi

Western Australia – Recreational (catch). Boat-based recreational catch between 1 September 2020 and 31 August 2021 from Ryan et al. [2022]. Please note that catches of Barramundi are underestimates as shore-based and boat-based fishers that only operated in freshwater were out of scope of the survey.

Western Australia – Recreational (management methods). A Recreational Fishing from Boat Licence 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 - Indigenous (management methods). The Fisheries Act 1988 (NT), specifies that: “Unless expressly provided otherwise, nothing in this Act derogates or limits the right of Aboriginal people who have traditionally used the resources of an area of land or water in a traditional manner to continue to use those resources in that area in that manner.”

Northern Territory – Charter (management methods). In the Northern Territory, charter operators are regulated through the same management methods as the recreational sector, but are subject to additional limits on licence and passenger numbers.

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

Queensland – Recreational Fishing (Catch). Data are based at the whole of Queensland level and derived from statewide recreational fishing surveys. Where possible, estimates have been converted to weight (tonnes) using best known conversion multipliers. Conversion factors may display regional or temporal variability. In the absence of an adequate conversion factor, data presented as number of fish.  

Queensland – Commercial (Catch). Queensland commercial and charter data has been sourced from the commercial fisheries logbook program. Further information available through the Queensland Fisheries Summary Report https://www.daf.qld.gov.au/business-priorities/fisheries/monitoring-research/data/queensland-fisheries-summary-report 

Queensland – Commercial (Management Methods). Harvest strategies are available at: https://www.daf.qld.gov.au/business-priorities/fisheries/sustainable/harvest-strategy  

Commercial catch of Barramundi - note confidential catch not shown.

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