*

Cobia are widespread in tropical and subtropical oceans globally. In Australia, the two biological stocks of Cobia (Northern and Eastern Australia) are sustainable.

Photo: Rosenstiel School of Marine and Atmospheric Science

Cobia has an almost worldwide distribution in tropical and sub-tropical waters, except in the Eastern Pacific Ocean [Fry and Griffiths 2010]. In Australia, Cobia is found from Cape Naturaliste in Western Australia, across and around northern Australia to Botany Bay in NSW [Hoese et al 2006].

The stock structure of Cobia across Australia is not known and the determination of population subdivision in large mobile marine pelagic fish species is often challenging due to a range of factors including large effective population sizes, high dispersal capacities, and lack of apparent physical barriers to gene flow.

In Australia, Cobia is not commonly encountered in large numbers and is not currently a specific target species in any state or Commonwealth fishery. It is therefore difficult to collect the relevant biological and catch and effort information to assess any putative individual stocks. Consequently, we have taken the conservative step of separating Cobia into two functional management units. This is based on a parsimonious separation at Torres Strait, based on the separation of populations of pelagic species at the Torres Strait biogeographic barrier, resulting from the Torres Strait land bridge between continental Australia and New Guinea that persisted through much of the late Pleistocene and separated Indian and Pacific Ocean taxa (e.g. Spanish mackerel [Moore et al. 2003], grey mackerel [Broderick et al. 2011].

In addition, fishing mortality is fairly equivalent across each management unit (low), therefore undertaking an assessment at the management unit scale is justified.

Here, assessment of stock status is presented at the management unit level—Northern Australia (Western Australia, Northern Territory, QLD Gulf of Carpentaria, and Commonwealth) and Eastern Australia (Queensland East Coast, NSW, and Commonwealth).

Eastern Australia

Cobia is a popular recreational species in Queensland with estimated recreational catches generally higher than the commercial sector. Whole of Queensland recreational harvest was estimated to be 19 t in 2019–20 [Webley et al. 2015; Teixeira et al. 2021]. In the commercial sector, Cobia is a byproduct species in the East Coast Inshore Fishery (ECIF), and subsequently the commercial catch is low, peaking at 40 t in 2008–09 and averaging 14 t for the last 10 years to 2021–22. The New South Wales commercial catch from 2015 to 2022 averaged approximately 1.5 t per year, and Cobia is not a major component of recreational landings [West et al. 2015; Murphy et al. 2020; Murphy et al. 2022]. Commonwealth commercial catch of Cobia averaged less than 1 t per year during 2017–18 to 2021–22 financial years and was less than 1 t in the 2021–22 financial year. Commonwealth fishing is unlikely to be having a negative impact on the stock. There have been no significant catches by Victorian fisheries, not surprising given this species is at the end of its southern range in this jurisdiction. The last reported catch in Victoria was in 2013–14, and less than 0.05 t was taken in any preceding year.

A preliminary assessment using Queensland recreational, commercial and charter catch data applied to a modified catch-MSY model (developed by Martell and Froese [2013] and modified by Haddon et al. [2018]), estimated that the 2019 biomass of Cobia was 76% of unfished levels [Saunders et al. 2020a]. This indicates that the biomass of this stock is unlikely to be depleted and that recruitment is unlikely to be impaired. Similarly, the fishing mortality in 2019 was 0.06 which was well below the limit reference point indicating that the current level of fishing mortality is unlikely to cause the stock to become recruitment impaired. Catch-MSY modelling has a higher degree of uncertainty and should not be solely relied on to make inferences about long-term biomass trends. However, Cobia has life history traits that are highly productive, including low age at maturity, high fecundity, and a broadcast spawning reproductive strategy [van der Velde et al. 2009]. Productive species may be more resilient to higher fishing pressure and given the low and consistent catch over the last decade, recruitment is unlikely to be impaired.

On the basis of the evidence provided above, Cobia in Eastern Australia is classified as a sustainable stock.

Cobia biology [van der Velde et al. 2009; Fry and Griffiths 2010]

Distribution of reported commercial catch of Cobia.

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 statewide 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 has been sourced from the commercial fisheries logbook program. Further information is 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  

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.”

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.

New South Wales – Recreational (Catch). Murphy et al. [2022] 

New South Wales – Indigenous (management methods). https://www.dpi.nsw.gov.au/fishing/aboriginal-fishing

Commonwealth – Commercial (Management Methods/Catch). Data provided for the Commonwealth align with 2021-22 financial year.

Commonwealth – Recreational. The Commonwealth does not manage recreational fishing in Commonwealth waters. Recreational fishing in Commonwealth waters is managed by the state or territory immediately adjacent to those waters, under its management regulations.  

Commonwealth – Indigenous.The Australian government does not manage non-commercial Indigenous fishing in Commonwealth waters, with the exception of Torres Strait. In general, non-commercial Indigenous fishing in Commonwealth waters is managed by the state or territory immediately adjacent to those waters. 

Commercial catch of Cobia

1. Divya, PR, Linu, J, Mohitha, Kathirvelpandian, A, Manoj, P, Basheer, VS and Gopalakrishnan, A 2019, Deciphering demographic history and fine-scale population structure of cobia, Rachycentron canadum (Pisces: Rachycentridae) using microsatellite and mitochondrial markers. Marine Biodiversity, 49, 381–393
2. Divya, PR, Linu, J, Mohitha, Kathirvelpandian, A, Manoj, P, Basheer, VS and Gopalakrishnan, A 2019, Deciphering demographic history and fine-scale population structure of cobia, Rachycentron canadum (Pisces: Rachycentridae) using microsatellite and mitochondrial markers. Marine Biodiversity, 49, 381–393
3. Fry, GC, and Griffiths, SP 2010, Population dynamics and stock status of cobia, Rachycentron canadum, caught in Australian recreational and commercial coastal fisheries, Fisheries Management and Ecology 17(3): 231–239
4. Haddon, M, Punt, A and Burch, P 2018, simpleSA: A package containing functions to facilitate relatively simple stock assessments. R package version 0.1.18.
5. Hoese, DF, Bray, DJ, Paxton, JR and, Allen, GR 2006, Fishes. In, Beesley, PL and Wells A (eds) Zoological Catalogue of Australia. Volume 35. ABRS & CSIRO Publishing: Australia Part 1, pp. xxiv 1-670; Part 2, pp. xxi 671-1472; part 3, pp. xxi 1473-2178
6. Joy, L, Mohitha, C, Divya, PR, Gopalakrishnan, A, Basheer, VS and Jena, JK 2016, Weak genetic differentiation in cobia, Rachycentron canadum from Indian waters as inferred from mitochondrial DNA ATPase 6 and 8 genes, Mitochondrial DNA Part A, 27:4, 2819-2821
7. Martell, S and Froese, R 2013, A simple method for estimating MSY from catch and resilience. Fish and Fisheries 14:504–514.
8. Matthews, SR, Penny, SS and Steffe, A 2019, A Survey of Recreational Fishing in the Greater Darwin Area 2015. Northern Territory Government, Australia. Fishery Report No 121.
9. Murphy, JJ, Ochwada-Doyle, FA, West, LD, Stark, KE and Hughes JM, 2020, The Recreational Fisheries Monitoring Program. Survey of recreational fishing in 2017–18, Fisheries final report series 158, NSW Department of Primary Industries, Wollongong.
10. Murphy, JJ, Ochwada-Doyle, FA, West, LD, Stark, KE, Hughes, JM, and Taylor, MD 2022, Survey of recreational fishing in NSW, 2019/20. NSW Department of Primary Industries, Nelson Bay, Fisheries Final Report Series No. 161. 80p.
11. Ryan, KL, Hall, NG, Lai, EK, Smallwood, CB, Tate, A, Taylor, SM and Wise, BS 2019, Statewide survey of boat-based recreational fishing in Western Australia 2017/18. Fisheries Research Report No. 297. Department of Primary Industries and Regional Development, Government of Western Australia, Perth.
12. Salari-Aliabadi, MA, Gilkolaei, SR, Savari, A, Zolgharnein, H and Nabavi, SMB 2009, Population Genetic structure of cobia, Rachycentron canadum Revealed by Microsatellite Markers. Journal of Applied Biological Sciences, 3:1, 103–107.
13. Saunders, T, Roelofs, A and Newman, S 2020, Eastern Australia Cobia Stock Status Summary—2020—unpublished fishery report.
14. Saunders, T, Roelofs, A and Newman, S 2020, Northern Australia Cobia Stock Status Summary—2020—unpublished fishery report.
15. Teixeira, D, Janes, R and Webley, J 2021, 2019–20 Statewide Recreational Fishing Survey Key Results. Project Report. State of Queensland, Brisbane.
16. van der Velde, TD, Griffiths, SP, and Fry GC 2009, Reproductive biology of the commercially and recreationally important cobia Rachycentron canadum in northeastern Australia, Fisheries Science 76: 33–43
17. Webley, J, McInnes, K, Teixeira, D, Lawson, A and Quinn, R 2015, Statewide Recreational Fishing Survey 2013–14. Department of Agriculture and Fisheries, Brisbane.
18. West, LD, Lyle, JM, Matthews, SR, Stark, KE and Steffe, AS 2012, Survey of recreational fishing in the Northern Territory, 2009/10. Northern Territory Fisheries. Department of Resources, Northern Territory. 128 pp.
19. West, LD, Stark, KE, Murphy, JJ, Lyle, JM and, Ochwada-Doyle, F 2015, Survey of Recreational Fishing in New South Wales and the ACT, 2013/14, Fisheries Final Report Series.