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Spangled Emperor has a wide distribution around Australia. There are eight stocks—defined at either the management unit or jurisdictional level—across WA, the NT, QLD and NSW. In WA three management units are sustainable and one is recovering. The NT jurisdictional stock is sustainable. In QLD one management unit is sustainable and one is undefined. The NSW management unit is negligible.

Spangled Emperor has a widespread Indo-West Pacific distribution, ranging from the Red Sea, Persian Gulf, and East Africa east to southern Japan in the north, around northern Australia and extending east to Samoa [Carpenter and Allen 1989]. In Australia, Spangled Emperor are found from around Rottnest Island on the lower west coast, across northern Australia to south of Sydney on the east coast [Carpenter and Allen 1989; Carpenter and Niem 2001].

The population structure of Spangled Emperor in Western Australia has been studied by assessing spatial variation in allozymes [Johnson et al. 1993], otolith microchemistry [Moran et al. 1993], tagging and recapture [Moran et al. 1993], DNA micro-satellite markers [Berry et al. 2012], and acoustic telemetry [Pillans et al. 2014]. Individuals generally demonstrate a limited home range of less than three nautical miles [Moran et al. 1993]. Relatively high site fidelity has been shown for at least some individuals in Western Australia and elsewhere [Chateau and Wantiez 2008; Pillans et al. 2014]. Limited mixing of post-settlement individuals is also indicated from an analysis of otolith microchemistry of Spangled Emperor sampled from different sites [Moran et al. 1993].

Genetic studies have demonstrated homogeneous genetic characteristics across broad spatial scales (10–1,500 km) throughout the distribution of Spangled Emperor in Western Australian [Johnson et al. 1993]. Analysis of fine-scale patterns using high resolution micro-satellite markers, however, has found that juveniles exhibit fine-scale genetic autocorrelation, which declines with age [Berry et al. 2012]. This implies both larval cohesion and limited juvenile dispersal prior to maturity, primarily in the vicinity of the Ningaloo Marine Park [Berry et al. 2012]. Hydrodynamic modelling indicated that Spangled Emperor larvae were likely to be transported hundreds of kilometres, easily accounting for the observed gene flow, despite relatively restricted adult dispersal [Berry et al. 2012]. As such, Spangled Emperor are considered to comprise a single biological stock in at least Western Australia. However, there is limited mixing of adult Spangled Emperor. Given the absence of any discrete genetic structure, there is insufficient evidence to suggest revision of current management boundaries. Hence, the current boundaries that designate separate management units are deemed appropriate if adequate levels of adult biomass are maintained, as declines in one stock may have broader implications for the population network given the broader connectivity.

There is a high likelihood that these population characteristics (extensive gene flow, limited adult movement) are shared across each of the jurisdictions. Low genetic subdivision between northwest Western Australia and the Great Barrier Reef suggests gene flow is likely to be high between these regions [Berry et al. 2012]. There is possibly one genetic stock in Australia, however, improved stock delineation work is required in jurisdictions outside Western Australia.

Here, assessment of stock status is presented at the management unit level—West Coast, Gascoyne, Pilbara, Kimberley (Western Australia); Gulf of Carpentaria (Queensland), East Coast (Queensland); and New South Wales; and at the jurisdictional level—Northern Territory.

East Coast Queensland

There has been no formal stock assessment of Spangled Emperor across the East Coast Queensland management unit. Estimated recreational harvest of Spangled Emperor in 2019–20 was 27 t at the whole of Queensland level (i.e., across both stocks) [Teixeira et al. 2021]. In 2004, decreased commercial catch coincided with expansion of no-take marine reserves within the Great Barrier Reef Marine Park and the introduction of a quota management system for coral reef finfish species. The annual reported commercial line harvest has been relatively stable with an average of 55 t over the last decade and catch of 51 t in 2021–22. Length and age frequencies collected from fishery dependent monitoring remain stable and showed that a strong year class entered the fishery in 2018–19, remaining dominant through to 2022–23 [QDAF Unpublished 2023]. The above evidence indicates recent strong recruitment and indicates that the biomass of this stock is unlikely to be depleted and recruitment is unlikely to be impaired.

Spangled Emperor is a secondary target and by-product species in the Reef Line Fishery (RLF). Commercial harvest is only constrained by a multi-species total allowable commercial catch (TACC) and a minimum legal size. However, additional harvest constraints are provided through species-specific harvest control rules and catch reference points introduced in early 2020 for secondary target species through the RLF Harvest Strategy [QDAF 2020]. Harvest of Spangled Emperor that exceeds the harvest reference points and control rules will trigger a stock assessment and the implementation of an interim species-specific TACC. Recreational harvest is also controlled through the minimum legal size and a possession limit. It is likely that a portion of the biomass would be afforded some protection from fishing through zoning (restricting or prohibiting fishing) in the Great Barrier Reef Marine Park, although this has not been quantified. 

Fishing pressure for Spangled Emperor has been stable over the last decade with nominal catch rates in the commercial sector averaging 16 kg/day. Fishing days peaked in 2009–10 at 4,529 days of effort before stabilising over the last decade to an average of 3,412 days of effort. Targeted catch and effort within the commercial fishery are limited to a small number of commercial operators in the northeast of the state due to market preferences for other species within the fishery. The above evidence indicates 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 East Coast of Queensland management unit is classified as a sustainable stock.

Gulf of Carpentaria

There has been no stock assessment of the species across this management unit. Spangled Emperor is a by-product species group in the Gulf of Carpentaria Line Fishery and Gulf of Carpentaria Developmental Fin Fish Trawl Fishery with low annual harvest (approximately 1 t average since 2012–22). Estimated recreational harvest of Spangled Emperor was 27 t at the whole of Queensland level (i.e., across both stocks) [Teixeira et al. 2021]. There are no reliable estimates of catch of Spangled Emperor for Indigenous fishers in the GOC, but it is reasonably expected to be very low. The above evidence of likely low harvest suggests that it is unlikely that the biomass of Spangled Emperor in the GOC is depleted, however there is insufficient information available to confidently classify the status of this stock.

On the basis of the evidence provided above, the Gulf of Carpentaria (Queensland) management unit is classified as an undefined stock.

Spangled Emperor biology [Currey et al. 2013; DAF unpublished data: Marriott et al. 2010, 2011]

Distribution of reported commercial catch of Spangled Emperor

Western Australia – Recreational (Catch). Boat-based recreational catch is from 1 September 2020–31 August 2021. These data are derived from those reported in Ryan et al. (2022).

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.

Western Australia – Commercial (Catch). Catch is unavailable as there were fewer than three vessels in the Pilbara Fish Trawl Interim Managed Fishery, Pilbara Trap Managed Fishery and West Coast Demersal Gillnet and Demersal Longline (Interim) Managed Fishery.

Western Australia – Active Vessels. Data are confidential as there were fewer than three vessels in the Pilbara Fish Trawl Interim Managed Fishery, Pilbara Trap Managed Fishery and West Coast Demersal Gillnet and Demersal Longline (Interim) Managed Fishery.

Western Australia – Commercial (Management Methods). Spangled Emperor forms part of the combined Total Allowable Commercial Catch for other mixed demersal species in the GDSMF.

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  

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

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.”

Commercial catch of Spangled Emperor - note confidential catch not shown

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