*

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.

Mackerel Managed Fishery

The Western Australian Mackerel Managed Fishery (MMF) predominantly targets Spanish Mackerel (Scomberomorus commerson). An age-based assessment of Spanish Mackerel in Western Australia is currently underway. The previous assessment, conducted during 1999–2002 when catches were higher than current levels, used catch and effort, biological information, age structure data, and yield-per-recruit modelling indicating the stock was sustainable and could sustain a high level of fishing [Mackie et al. 2003]. Ongoing Catch-MSY analysis (SimpleSA package) infers the Western Australia stock is likely to be above the target biomass and is stable at current catch levels, which are below the estimated MSY. 

Catch and fishing effort throughout the MMF have been relatively stable since 2006, following the introduction of quotas and reductions in vessels due to management changes, with total catches mostly within the tolerance range (246–430 t) [Newman et al. 2023]. The catch rates for the two main northern fishery areas (Kimberley and Pilbara, covering Exmouth to the Northern Territory border), have declined over recent years due mainly to major changes in operators, but remain above historical levels, indicating a relatively high but possibly declining abundance of Spanish Mackerel in these management areas. Catch rates in the southern (Gascoyne–West Coast) area have declined in recent years, after the influence of the 2011 heatwave that apparently increased abundance of Spanish Mackerel for a period in southern WA [Pearce et al. 2011]. Additionally, the average sizes recorded in the commercial and charter catches have been stable since 2006 and the catch distributions have not markedly changed over this period. Thus, based on the available information, the weight of evidence assessment [Lewis 2020] determined it is likely that there is an acceptable moderate depletion of the stock. The above evidence indicates that the biomass of this stock is unlikely to be depleted.

The total commercial catch of Spanish Mackerel in Western Australia for 2021 was 238 t, below the tolerance range of 246–430 t. Apart from 2021 and a similar catch in 2018, the catches have been within the tolerance range for most years since management changes in 2006. The charter catch has been stable since 2008, between 14–20 t. The estimated boat based recreational fishing harvest weights of Spanish Mackerel have declined from 69–109 t to 35–78 t (95% confidence intervals), between the 2011–12 to 2020–21 statewide surveys, respectively [Ryan et al. 2022]. The lower recent recreational catch estimate can be attributed in part to declining recreational effort levels in the northern bioregions, and also to a likely lower abundance associated with lower water temperatures in the West Coast Bioregion, as is reflected in the lower commercial catches and catch rates. A PSA and previous Yield Per Recruit (YPR) analysis suggests the species has a low risk of overexploitation with appropriate management. The minimum size limit for Spanish Mackerel in Western Australia (900 mm TL) is similar to the size at maturity for this species [Mackie et al. 2003], which helps with sustainability as commercial line fishers avoid areas with undersize fish and means that the spawning stock is essentially the same as the exploited stock. Thus, the weight of evidence assessment concluded the current management settings are maintaining risk to the stock at acceptable, medium levels. 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, the Mackerel Managed Fishery (Western Australia) management unit 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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