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Sea Mullet is a sustainable species occurring in all coastal regions of WA, and on the east coast of Australia.

Sea Mullet (Mugil cephalus) was formerly regarded as a single species with a global distribution; however recent genetic evidence indicates that they are in fact a complex of many cryptic species. Sea Mullet along the west and east coasts of Australia are regarded as distinct species [Durand et al. 2012; Krück et al. 2013]. The population structure within Western Australia is yet to be fully examined but given the extensive coastline and wide latitudinal range, it is possible that this jurisdiction hosts more than one biological stock (or species). Given this uncertainty, Sea Mullet within each Bioregion are currently managed as separate units. Limited tagging and genetic studies [Thomson 1951; Watts and Johnson 1994] suggest mixing of fish throughout the West Coast Bioregion (WCB), where most of the catch is taken. Extensive tagging studies [Kesteven 1953] suggest a single east coast biological stock of Sea Mullet, extending from central Queensland to eastern Victoria. 

Here, assessment of stock status is presented at the jurisdictional stock level for Western Australia and the biological stock level for Eastern Australia.

Eastern Australia

This cross-jurisdictional biological stock is fished in Queensland and New South Wales. Each jurisdiction monitors the part of the biological stock that occurs in its waters. The status presented here for the entire biological stock has been established using evidence from both jurisdictions.

The most recent stock assessment estimated that at the end of 2020 the Eastern Australia biological stock of Sea Mullet was at approximately 37% of unfished levels [Lovett et al. 2022], and above the limit reference point of 20%. The stock assessment used a two-sex, age-structured population model, fit to age and length data, and constructed within the Stock Synthesis modelling framework. Eight scenarios were run, covering a range of modelling assumptions. None of the model scenarios indicated that the biomass of Sea Mullet had declined to below the limit reference point of 20% of unfished levels at any time during the history of the assessment (1899 to 2020). The stock is not considered to be recruitment impaired. 

The total landed catch (New South Wales and Queensland combined) in 2020 was approximately 4102 t and below the estimated Maximum Sustainable Yield (MSY) of 5353 t [Lovett et al. 2022]. The relative biomass at 37% of unfished levels was above the estimated biomass at MSY, being 33% of unfished levels. This level of fishing mortality is unlikely to cause the stock to become recruitment impaired.

Since the final year modelled in the stock assessment (2020), nominal catch rates in the New South Wales estuary fishery have increased, whereas in the Queensland Ocean Beach Fishery they declined substantially, likely due to adverse weather conditions during the fishing season [Stewart 2023]. Harvest and fishing effort in New South Wales have been at historical lows. Recent age composition data for New South Wales show a strong year class moving through the fishery, first identified as 2-year old fish in 2018 through to 6 year old fish in 2022. The age compositions in the most recent years (2021 and 2022) show a good spread of ages in the fishery [Stewart 2023]. In Queensland recent harvest (918 t in 2021–22) was less than half the long-term average of 1,980 t (1988–22). This reduction may be due to a range of factors including management changes, licence buy backs, marine park expansion into historic fishing areas, introduction of TACC and subsequent reporting requirements in 2021, and an ageing demographic of fishers. Length and age frequency information from routine monitoring show stability in the sizes of fish being harvested and evidence of recent strong year classes. Nominal effort in the Queensland component of the fishery has reduced markedly from 7,563 days in 2015–16 to 2,503 in 2021–22, and the number of fishers reporting ‘Mullet - (unspecified)’ catch has reduced from 250 fishers to 164 fishers during the same period. These trends indicate that the stock and fisheries in both jurisdictions have not changed substantially since the final year in the last stock assessment, being 2020 [Lovett et al. 2022]. 

On the basis of the evidence provided above, the entire Eastern Australian biological stock is classified as a sustainable stock.itoring show stability in the sizes of fish being harvested and evidence of recent strong year classes. Nominal effort in the Queensland component of the fishery has reduced markedly from 7,563 days in 2015–16 to 2,503 in 2021–22, and the number of fishers reporting ‘Mullet - (unspecified)’ catch has reduced from 250 fishers to 164 fishers during the same period. These trends indicate that the stock and fisheries in both jurisdictions have not changed substantially since the final year in the last stock assessment, being 2020 [Lovett et al. 2022]. 

On the basis of the evidence provided above, the entire Eastern Australian biological stock is classified as a sustainable stock

Sea Mullet biology [Virgona et al. 1998; Smith and Deguara 2002; Gaughan et al. 2006; Fisheries Queensland 2018]

Distribution of reported commercial catch of Sea Mullet

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

Queensland – Commercial (Catch). Queensland commercial and charter data have been sourced from the commercial fisheries logbook program. Further information are 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 – Indigenous (Management Methods). https://www.dpi.nsw.gov.au/fishing/aboriginal-fishing

Commercial catch of Sea Mullet - note confidential catch not shown

1. Duffy, R, Harris, D, Fisher, E, Smith, K, Johnston, D, Denham, A, Hesp, A, Hodgson, B, Quinn, A and Newman, M 2022, South-West Estuarine and Nearshore Finfish Resource Part 1: Sea Mullet and Yellowfin Whiting Mullet and Yellowfin Whiting, Fisheries Research Report No. 322.
2. Durand, JD, Chen, WJ, Shen, KN, Jamandre, BW, Blel, H and Diop, K 2012, Systematics of the grey mullets (Teleostei: Mugiliformes: Mugilidae): molecular phylogenetic evidence challenges two centuries of morphology-based taxonomy, Molecular Phylogenetics and Evolution, 64 73–92.
3. Fisheries Queensland 2018, Fisheries Queensland monitoring data 1999–2018, Monitoring our fisheries, Queensland Department of Agriculture and Fisheries.
4. Fowler, AM, Smith, SM, Booth, DJ and Stewart, J 2016, Partial migration of grey mullet (Mugil cephalus) on Australia’s east coast revealed by otolith chemistry, Marine Environmental Research, 119: 238–244.
5. Froese, R, Demirel, N, Coro, G, Kleisner, KM and Winker, H 2017, Estimating fisheries reference points from catch and resilience, Fish and Fisheries, 18: 506-526.
6. Kesteven, GL 1953, Further results of tagging sea mullet, Mugil cephalus Linnaeus, on the eastern Australian coast, Australian Journal of Marine and Freshwater Research, 4: 251–306.
7. Krück, NC, Innes, DI and Ovenden, JR 2013, New SNPs for population genetic analysis reveal possible cryptic speciation of eastern Australian sea mullet (Mugil cephalus), Molecular Ecology Resources, 13: 715–725. doi:10.1111/1755-0998.12112.
8. Lovett, R, Prosser, A and Stewart, J 2022, Stock assessment of Australian east coast sea mullet (Mugil cephalus) with data to December 2020, Technical Report. State of Queensland, Brisbane, 48pp.
9. Pedersen, MW and Berg, CW 2017, A stochastic surplus production model in continuous time. Fish and Fisheries, 18(2), 226–243.
10. Smith, KA and Deguara, KL 2002, Review of biological information and stock assessment for the NSW sea mullet resource, NSW Fisheries Resource Assessment Series No. 12, New South Wales Fisheries, Cronulla.
11. Stewart, J 2023, NSW Stock Status Summary 2021/22 – Sea Mullet (Mugil cephalus). NSW Department of Primary Industries, Fisheries. 13 pp
12. Stewart, J, Hegarty, A, Young, C and Fowler, AM 2018, Sex-specific differences in growth, mortality and migration support population resilience in the heavily exploited migratory marine teleost Mugil cephalus (Linnaeus 1758), Marine and Freshwater Research 69: 385–394.
13. Thomson, JM 1951, Growth and habits of the sea mullet, Mugil dobula Gunther, in Western Australia, Australian Journal of Marine and Freshwater Research, 2: 193–225.
14. Virgona, JL, Deguara, KL, Sullings, DJ, Halliday, I and Kelly, K 1998, Assessment of the stocks of sea mullet in New South Wales and Queensland Waters, Final Report Series No. 2, New South Wales Fisheries, Cronulla.
15. Watts, RJ and Johnson, MS 2004, Estuaries, lagoons and enclosed embayments: habitats that enhance subdivision of inshore fishes, Marine and Freshwater Research, 55: 641–651.
16. Winker, H, Carvalho, F, and Kapur, M 2018, JABBA: Just Another Bayesian Biomass Assessment. Fisheries Research, 204, 275–288.