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The Torres Strait Spanish mackerel fishery commenced in 1941. The fishery for Spanish mackerel is by line fishing only and managed as a single stock. Spanish mackerel are important to the Torres Strait people and fishing culture. They are an economic and traditional food source. The Australian Fisheries Management Authority commissioned annual updates to the Torres Strait Spanish mackerel stock assessment for three years 2021–2023. This was to support quota management and to monitor spawning biomass estimates. This stock assessment analysed data up to June 2023. The assessment was overseen by the Torres Strait Finfish Fishery Resource Assessment Group (TSFFRAG). Across analyses, the median estimated spawning biomass of Spanish mackerel in the 2022–2023 financial year (labelled the 2023 fishing year) was 41 percent of unfished estimates at the start of the fishery in 1941.

The Torres Strait Spanish mackerel fishery commenced in 1941. The fishery for Spanish mackerel is by line fishing only and managed as a single stock. Spanish mackerel are important to the Torres Strait people and fishing culture. They are an economic and traditional food source. The Australian Fisheries Management Authority commissioned annual updates to the Torres Strait Spanish mackerel stock assessment for three years 2021–2023. This is to support quota management and to monitor spawning biomass estimates. This stock assessment, the year-two project report, analysed data up to June 2022. The assessment was overseen by the Torres Strait Finfish Fishery Resource Assessment Group (TSFFRAG). Across analyses, the median estimated spawning biomass of Spanish mackerel in the 2021–2022 financial year (labelled the 2022 fishing year) was 31 percent of unfished estimates at the start of the fishery in 1941.

Spanish mackerel, Scomberomorus commerson, sustain an important finfish line fishery within the Torres Strait and are managed as a single stock. In these waters the species have been recorded to live for up to 13 years, weigh in excess of 20 kg and mature from two years of age. The Australian Fisheries Management Authority (AFMA) commissioned annual updates to the Torres Strait Spanish mackerel stock assessment for three years 2021–2023. This was to monitor biomass estimates that were close to the 20 percent limit reference point for declaring an overfished stock. Across analyses of different fish natural mortality and harvest, the median estimated spawning biomass of Spanish mackerel in 2020 was 29 percent of unfished estimates at the start of the fishery in 1940. The low biomass result was due to the high harvests between 1980 and 2006 and the downturn in Spanish mackerel catch rates 2010–2019. The 2022–2023 recommended biological catch (RBC) of Spanish mackerel for all fishing sectors in the Torres Strait was 95 t based on the median forecast estimate (Table 1). This RBC was forecast to build Spanish mackerel towards a target biomass of 48% within 12 years, and have less than 10% risk of reducing to the 20% biomass limit reference point. The assessment work also initiated the first comparison of the packaged stock assessment software stock synthesis (SS), which was used for assessing Australian east coast and Gulf of Carpentaria Spanish mackerel. The SS estimate of spawning biomass ratio in 2020 was similar compared against the current model developed by the Department of Agriculture and Fisheries and reported herein. SS performance and results will be further tested in years two and three of this AFMA project, noting that future provision of a streamlined stock assessment is to transition to stock synthesis after TSFFRAG review.

The overarching goal of this project was to prepare a document that summarises past, present and emerging ways in which research using genetic technology can assist the Australian fishing industry to maintain productive and sustainable harvests. The project achieved the following specific objectives: 1. Documented existing and prospective biotechnologies and genetic analysis tools that are relevant to wild fisheries management, and their availability and application at a national and international level; 2. Documented the FRDC’s past and current investment in biotechnology and genetic tools used in wild fisheries management research; 3. Documented the different biotechnology and genetic tools that are being used in wild fisheries management research in Australia, and the nature and location of key research groups; 4. Described what management question each tool has been used for (e.g. stock structure, biomass estimation, product provenance, disease monitoring); 5. Identified those tools and approaches (existing and future) most likely to deliver significant advances in fisheries management; 6. Identified the potential for collaborations which could improve the focus and impact of work in this area.

OBJECTIVES: 1. Analyse current monitoring and logbook data sets, as well as survey and other information,to establish whether these data provide sufficient power to develop critical indicators of fishery performance. 2. Provide a risk analysis that examines the use of age structure and catch rate information for development of critical indicators, and response rules for those criteria, in the absence of other fishery information. 3. Develop a monitoring program that uses commercial vessels from the fishery to provide independent data.

The stable isotopes of delta O-18 and delta C-13 in sagittal otolith carbonates were used to determine the stock structure of Grey Mackerel, Scomberomorus semifasciatus. Otoliths were collected from Grey Mackerel at ten locations representing much of their distributional and fisheries range across northern Australia from 2005 to 2007. Across this broad range (similar to 6500 km), fish from four broad locations-Western Australia (S1), Northern Territory and Gulf of Carpentaria (S2, S3, S4, S5, S6, S7), Queensland east coast mid and north sites (S8, S9) and Queensland east coast south site (S10)-had stable isotope values that were significantly different indicating stock separation. Otolith stable isotopes differed more between locations than among years within a location, indicating temporal stability across years. The spatial separation of these populations indicates a complex stock structure across northern Australia. Stocks of S. semifasciatus appear to be associated with large coastal embayments. These results indicate that optimal fisheries management may require a review of the current spatial arrangements, particularly in relation to the evidence of shared stocks in the Gulf of Carpentaria. Furthermore, as the population of S. semifasciatus in Western Australia exhibited high spatial separation from those at all the other locations examined, further research activities should focus on investigating additional locations within Western Australia for an enhanced determination of stock delineation. From the issue entitled "Proceedings of the 4th International Otolith Symposium, 24-28 August 2009, Monterey, California"

Aim: This study investigated the use of stable δ13C and δ18O isotopes in the sagittal otolith carbonate of narrow-barred Spanish mackerel, Scomberomorus commerson, as indicators of population structure across Australia. Location: Samples were collected from 25 locations extending from the lower west coast of Western Australia (30°), across northern Australian waters, and to the east coast of Australia (18°) covering a coastline length of approximately 9500 km, including samples from Indonesia. Methods: The stable δ13C and δ18O isotopes in the sagittal otolith carbonate of S. commerson were analysed using standard mass spectrometric techniques. The isotope ratios across northern Australian subregions were subjected to an agglomerative hierarchical cluster analysis to define subregions. Isotope ratios within each of the subregions were compared to assess population structure across Australia. Results: Cluster analysis separated samples into four subregions: central Western Australia, north Western Australia, northern Australia and the Gulf of Carpentaria and eastern Australia. Isotope signatures for fish from a number of sampling sites from across Australia and Indonesia were significantly different, indicating population separation. No significant differences were found in otolith isotope ratios between sampling times (no temporal variation). Main conclusions: Significant differences in the isotopic signatures of S. commerson demonstrate that there is unlikely to be any substantial movement of fish among these spatially discrete adult assemblages. The lack of temporal variation among otolith isotope ratios indicates that S. commerson populations do not undergo longshore spatial shifts in distribution during their life history. The temporal persistence of spatially explicit stable isotopic signatures indicates that, at these spatial scales, the population units sampled comprise functionally distinct management units or separate ‘stocks’ for many of the purposes of fis

The requirement for Queensland, Northern Territory and Western Australian jurisdictions to ensure sustainable harvest of fish resources and their optimal use relies on robust information on the resource status. For grey mackerel (Scomberomorus semifasciatus) fisheries, each of these jurisdictions has their own management regime in their corresponding waters. The lack of information on stock structure of grey mackerel, however, means that the appropriate spatial scale of management is not known. As well, fishers require assurance of future sustainability to encourage investment and long-term involvement in a fishery that supplies lucrative overseas markets. These management and fisher-unfriendly circumstances must be viewed in the context of recent 3-fold increases in catches of grey mackerel along the Queensland east coast, combined with significant and increasing catches in other parts of the species' northern Australian range. Establishing the stock structure of grey mackerel would also immensely improve the relevance of resource assessments for fishery management of grey mackerel across northern Australia. This highlighted the urgent need for stock structure information for this species. The impetus for this project came from the strategic recommendations of the FRDC review by Ward and Rogers (2003), "Northern mackerel (Scombridae: Scomberomorus): current and future research needs" (Project No. 2002/096), which promoted the urgency for information on the stock structure of grey mackerel. In following these recommendations this project adopted a multi-technique and phased sampling approach as carried out by Buckworth et al (2007), who examined the stock structure of Spanish mackerel, Scomberomorus commerson, across northern Australia. The project objectives were to determine the stock structure of grey mackerel across their northern Australian range, and use this information to define management units and their appropriate spatial scales. We used multiple techniqu

The scombrid Scomberomorus semifasciatus is an important component of inshore fisheries in tropical Australia. Data on the parasite fauna of 593 fish from areas off northern and eastern Australia were examined for evidence of discrete fish populations. The parasites used were juveniles of Pterobothrium pearsoni, Callitetrarhynchus gracilis, Anisakis simplex (sensu latu) and Terranova sp. Tukey Kramer pairwise comparisons gave significant differences in the abundances of two or more parasites between fish from the east coast, the eastern Gulf of Carpentaria and the remainder of northern Australia. Multivariate analysis gave further evidence of differences and the results suggest that at least 4 populations or stocks of grey mackerel occur along the northern and eastern coastline of Australia.

Decisions about the allocation of management responsibilities for fisheries for narrow-barred Spanish mackerel, Scomberomorus commerson, as well as on-going stock assessments, require an understanding of the spatial relationships of the species. We used a suite of methods, isotope ratios in otoliths (earbones), parasite abundances, and genetic analyses (allozyme, mitochondrial DNA (mtDNA), and microsatellite DNA (msDNA) methods), to examine the spatial stock structure of Spanish mackerel. Fish were sampled from across northern Australia, and from Kupang (Indonesia). Project objectives included describing stock structure of the northern Australian stock of Spanish mackerel, advising on the appropriate scale of assessment and management for the stock, and comparison with material from Kupang (West Timor, Indonesia).

Concerns about Australian bycatch issues lead to the development of an innovative bycatch reduction system designed for Australian trawling conditions. The system, known as the Australian trawl efficiency device (AusTED), incorporates features of previous TEDs, but includes a flexible grid. The AusTED was tested at five selected locations, which ranged from shallow, estuarine, mud-bottom sites to deep-water, oceanic, sand-bottom sites. No significant differences were observed in prawn catch rates between control and AusTED equipped nets. Sea turtles and large stingrays were excluded from the AusTED equipped net and non-commercial bycatch was significantly reduced at most sites trawled. The AusTED system has the potential to be developed to suit the bycatch exclusion requirements of prawn trawl fisheries around Australia. Its acceptance by the fishing industry will depend upon the minimisation of prawn losses.