*

Spanish Mackerel are widely distributed across several fisheries in WA, NT, Qld, NSW and the Torres Strait. Three of the five stocks are sustainable, the Gulf of Carpentaria stock is depleting, and the East Coast stock is depleted.

In Australia there are three distinct genetic stocks of Spanish Mackerel (Scomberomorus commerson) as determined using single nucleotide polymorphisms (SNPs): a northern/western Australia stock, which extends from Perth in Western Australia across the Northern Territory and the Queensland waters of the Gulf of Carpentaria, a Torres Strait stock, and an east coast Australian stock, which spans from Cape York in north Queensland waters, to its southern extent in northern New South Wales [Williams et al. 2022]. 

Using SNPs methodology, Williams et al. [2022] provided higher resolution than previous genetics studies which used allozyme, mitochondrial DNA, and microsatellite DNA [Buckworth et al. 2007]. Of note, all studies consistently supported the existence of these three separate stocks. However, evidence from otolith microchemistry, parasite analysis and limited adult movement (at scales greater than 100 km) indicates the likely existence of smaller adult stocks with limited interaction [Lester et al. 2001; Moore et al. 2003; Buckworth et al. 2007]. 

While the northern/western Australia biological stock extends over multiple jurisdictions, there is evidence of limited adult movement and differences in biological and fishery characteristics for this stock [Mackie et al. 2003]. Consequently, we have taken the conservative step of assessing the northern/western stock at the jurisdictional level. Conversely, while the east coast Australian stock also extends over multiple jurisdictions, there is evidence of large movements along latitudinal gradients between north Queensland and northern New South Wales. In addition, joint stock assessments for the east coast were undertaken at the biological stock level. 

Here, assessment of stock status is presented at the biological stock level—Torres Strait Spanish Mackerel Fishery (Commonwealth) and East Coast (Queensland and New South Wales); management unit level—Mackerel Managed Fishery (Western Australia), Gulf of Carpentaria (Queensland); and jurisdictional level—Northern Territory.

Northern Territory

The harvest of Spanish Mackerel in the Northern Territory is managed through a catch-sharing arrangement between all user groups [NTG 2009]. This agreement aims to maintain the cumulative harvest of Spanish Mackerel within a precautionary allowable catch of 450 t per annum. The proportion of the allowable catch allocated to each user group was based on historical logbook data and catch estimates from the National Recreational and Indigenous Fishing Survey [Henry and Lyle 2003] as follows: 76% (342 t) to Spanish Mackerel Fishery licensees, 3% (13.5 t) to Offshore Net and Line Fishery licensees, 1% (4.5 t) to Demersal Fishery licensees, 3% (13.5 t) to Fishing Tour Operator licensees, 16% (72 t) to recreational fishers and 1% (4.5 t) to Indigenous fishers.

The cumulative catch by all sectors ranged from 319 to 560 t, at an annual average of 441 t for the 10 years spanning 2013–22. The proportion of the catch caught by each sector during this time approximated the allocations described above (i.e. 71%, 4%, < 1%, 3%, 13% and 2%, respectively). 

The most recent assessment of the Spanish Mackerel resource in the Northern Territory (using data to 2019) indicated that stocks are unlikely to have dropped below 68% of the unfished biomass and that the biomass at the conclusion of 2019 was 72% of the unfished level [Grubert et al. unpublished]. The above evidence indicates that the biomass of this stock is unlikely to be depleted. 

The same assessment indicated that the relative fishing mortality rate (i.e. U₂₀₁₉/U_MSY) in 2019 for the Northern Territory stock of Spanish Mackerel was 0.43, less than half of the rate required to achieve MSY. The current level of fishing mortality is unlikely to cause the stock to become recruitment impaired.

On the basis of the evidence provided above, Spanish Mackerel in the Northern Territory is classified as a sustainable stock.

Spanish Mackerel biology [McPherson 1992; McPherson 1993; QDAFF 2013]

Commonwealth – Commercial (Active vessels). Total number of TIB licences; this is not an indicator of licence activity.

Commonwealth – Commercial (Management Methods/Catch). Data provided for the Commonwealth align with 2021–22 financial year.

Commonwealth – Recreational. The Australian Government does not manage recreational fishing, including charter fishing, in Commonwealth waters. Recreational and charter fishing in Commonwealth waters is managed by the state or territory immediately adjacent to those waters, under its management regulations.

Commonwealth – Indigenous. (a) The Australian Government does not manage non-commercial Indigenous fishing in Commonwealth waters, with the exception of the Torres Strait. In general, non-commercial Indigenous fishing in Commonwealth waters is managed by the state or territory immediately adjacent to those waters. In the Torres Strait, both commercial and non-commercial Indigenous fishing is managed by the Torres Strait Protected Zone Joint Authority (PZJA) through the Australian Fisheries Management Authority (Commonwealth); the Department of Agriculture, Fisheries and Forestry (Queensland); and the Torres Strait Regional Authority. The PZJA also manages non-Indigenous commercial fishing in the Torres Strait; and (b) Subject to the defence that applies under 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.

Western Australia – Recreational (Catch). Western Australian boat-based recreational catch surveys from 1 Sept 2020–30 Aug 2021 [Ryan et al 2022]. Shore-based recreational catches are largely unknown.

Western Australia – Recreational (Management Methods). Western Australian boat-based recreational licence required.

Western Australia – Charter (Catch). Estimate based on numbers of fish caught multiplied by their average weight.

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 license and passenger numbers.

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.”

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 state-wide 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 have 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  

New South Wales – Recreational (Catch). Murphy et al. [2020].

New South Wales – Indigenous (Management Methods). More information available at: https://www.dpi.nsw.gov.au/fishing/aboriginal-fishing

Commercial catch of Spanish Mackerel - note confidential catch not shown. Years shown on this graph are Australian financial years (e.g. 2015 refers to the financial year beginning 01 July 2014 and ending 30 June 2015).

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