Sea Mullet (2023)
Mugil cephalus
Date Published: June 2023
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Summary
Sea Mullet is a sustainable species occurring in all coastal regions of WA, and on the east coast of Australia.
Stock Status Overview
Jurisdiction | Stock | Stock status | Indicators |
---|---|---|---|
Western Australia | Western Australia | Sustainable | Catch, CPUE, length and age compositions, fishing mortality, spawning stock biomass |
Stock Structure
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.
Stock Status
Western Australia
Sea Mullet (Mugil cephalus) is primarily targeted by the commercial net fishing sector, with catches by the recreational sector and customary fishers likely to be low relative to commercial catches. The commercial catch of sea mullet in the South, West and Gascoyne Coast bioregions shows a gradual increase from 1941 to around 1980, peaking at just under 700 t. However, changes in management and market demand led to a reduction in effort and commercial targeting of sea mullet, and catches have since declined to their current annual level of around 200 t. Over the past five years, 62% of the catch was taken by haul netting, 19% by beach seining and 19% by gillnetting.
A stock assessment for Sea Mullet was completed in 2022 [Duffy et al 2022] using the Western Australian Department of Primary Industries and Regional Development’s risk-based Weight of Evidence approach. This assessment considered catch (including catch-MSY (maximum sustainable yield) analyses), effort, catch distribution, standardised catch per unit effort (CPUE), vulnerability and susceptibility to fishing (PSA) analysis, age and length composition data, catch curve estimates of (long-term average) fishing mortality, and a non-state space biomass dynamic model applied to nominal CPUE data. Based on a combination of relatively low recent annual catches, light-moderate truncation of age structures for fish from the Gascoyne region (assumed to be representative of the spawning stock) and estimates of current biomass and fishing mortality that were BMSY and below FMSY, respectively, the assessment concluded that the stock is sustainable.
More recently, additional analyses for Sea Mullet in Western Australia involving the use of two more sophisticated (state space) biomass dynamics models, including ‘Just Another Bayesian Biomass Assessment (JABBA) [Winker et al. 2018] and ‘Surplus Production model in Continuous-Time’ (SPiCT) [Pederseen and Berg, 2018], applied to standardised CPUE (adjusted for assumed changes in fishing efficiency), yielded similar but slightly less optimistic results than produced in the previous assessment (DPIRD, unpublished data). Outputs from the recent analysis using the JABBA assessment model, for example, suggest that the current level of catch of approximately 200 t is well below the estimated Maximum Sustainable Yield (MSY) for the stock of 749 t (95% CLs: 515–1,808t). The JABBA point estimate for current biomass is at MSY (i.e. B/BMSY=1.0, 95% CLs: 0.67–1.45), and the estimate for current fishing mortality is well below FMSY (i.e. F/FMSY= 0.22, 95% CLs: 0.08–0.42). Thus, these results from the recent biomass dynamics modelling indicate that the stock is sustainable, and that overfishing is highly unlikely to be occurring.
The above evidence indicates that the biomass of this stock is unlikely to be depleted and that recruitment is unlikely to be impaired. Furthermore, 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 Western Australia jurisdictional stock of Sea Mullet is classified as a sustainable stock.
Biology
Sea Mullet biology [Virgona et al. 1998; Smith and Deguara 2002; Gaughan et al. 2006; Fisheries Queensland 2018]
Species | Longevity / Maximum Size | Maturity (50 per cent) |
---|---|---|
Sea Mullet | Western Australia 12 years, 790 mm FL; Eastern Australia 16 years, 640 mm FL |
Western Australia Males and Females 370 mm TL; Eastern Australia Males 300 mm TL, Females 330 mm TL |
Tables
Western Australia | |
---|---|
Commercial | |
Gillnet | |
Beach Seine | |
Haul Seine | |
Recreational | |
Hook and Line | |
Cast Net | |
Coastal, Estuary and River Set Nets | |
Indigenous | |
Net | |
Unspecified |
Method | Western Australia |
---|---|
Commercial | |
Gear restrictions | |
Limited entry | |
Spatial closures | |
Vessel restrictions | |
Indigenous | |
Bag limits | |
Gear restrictions | |
Recreational | |
Bag/possession limits | |
Gear restrictions | |
Licence | |
Spatial closures |
Western Australia | |
---|---|
Commercial | 179.36t |
Charter | Negligible |
Indigenous | Unknown |
Recreational | Insufficient data |
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
References
- 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.
- 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.
- Fisheries Queensland 2018, Fisheries Queensland monitoring data 1999–2018, Monitoring our fisheries, Queensland Department of Agriculture and Fisheries.
- 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.
- 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.
- 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.
- 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.
- 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.
- Pedersen, MW and Berg, CW 2017, A stochastic surplus production model in continuous time. Fish and Fisheries, 18(2), 226–243.
- 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.
- Stewart, J 2023, NSW Stock Status Summary 2021/22 – Sea Mullet (Mugil cephalus). NSW Department of Primary Industries, Fisheries. 13 pp
- 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.
- 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.
- 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.
- 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.
- Winker, H, Carvalho, F, and Kapur, M 2018, JABBA: Just Another Bayesian Biomass Assessment. Fisheries Research, 204, 275–288.