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Estuary Cobbler (2020)

Cnidoglanis macrocephalus

  • Rodney Duffy (WA Department of Primary Industries and Regional Development)
  • Amy Smoothey (NSW Department of Primary Industries)

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Summary

WA has two stocks of Estuary Cobbler: a sustainable stock in west coast estuaries and a recovering stock in south coast estuaries. Stock in NSW estuaries is undefined.

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Stock Status Overview

Stock status determination
Jurisdiction Stock Stock status Indicators
New South Wales New South Wales Estuary General Undefined
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Stock Structure

Estuary Cobbler are distributed across the southern half of Australia [Kowarsky 1975]. They occur in estuaries, embayments and marine environments but most of the commercial catch is taken in estuarine waters [Smith et al. 2018]. A study in Western Australia found that there are genetic differences between estuarine populations and adjacent marine populations [Ayvazian et al. 1994], indicating that stock structure is complex and that there may be a number of separate biological stocks. No genetic information is available for the east coast stock. Consequently, the biological stock structure of Estuary Cobbler is not well understood.

Here, assessment of stock status is presented at the Management Unit level—Western Australia West Coast Estuaries, Western Australia South Coast Estuaries and New South Wales Estuary General.

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Stock Status

New South Wales Estuary General

Since 2009, commercial catches of Estuary Cobbler in New South Wales have ranged between 6 and 21 tonnes (t) per year with the majority caught using mesh nets. In the Estuary General Fishery, Estuary Cobbler is taken largely as by-catch or by-product. As in Western Australia, most of the NSW Estuary Cobbler catch comes from a small number of estuaries, with the Clarence River contributing the greatest proportion. During the past seven years, catches have consistently been stable between 12.5 and 17.5 t, increasing from 6 t in 2017 to 12.6 t in 2018–19. While the total recreational and indigenous harvest is unknown, it is thought that those caught by recreational fishers are mostly released alive [West et al 2015].  There is insufficient information to confidently classify the status of this stock.

On the basis of the evidence provided above, Estuary Cobbler in New South Wales is classified as an undefined stock.

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Biology

Estuary Cobbler biology [Chuwen et al. 2011]

Biology
Species Longevity / Maximum Size Maturity (50 per cent)
Estuary Cobbler 20 years [New South Wales, unpublished], 700 mm Unknown
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Distributions

Distribution of reported commercial catch of Estuary Cobbler
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Tables

Fishing methods
New South Wales
Commercial
Mesh Net
Various
Indigenous
Spearfishing
Hook and Line
Recreational
Spearfishing
Hook and Line
Management methods
Method New South Wales
Commercial
Fishing gear and method restrictions
Limited entry
Spatial closures
Temporal closures
Indigenous
Customary fishing management arrangements
Recreational
Bag limits
Gear restrictions
Licence
Spatial zoning
Catch
New South Wales
Commercial 12.56t
Indigenous Unknown
Recreational Unknown

Western Australia – Recreational (Management methods) In Western Australia a recreational fishing license is only required for fishing from a boat

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

New South Wales – Recreational (Catch) Murphy et al. [2020].

 

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Catch Chart

Commercial catch of Estuary Cobbler - note confidential catch not shown
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References

  1. Ayvazian, SG, Johnson, MS and McGlashan, DJ 1994, High levels of genetic subdivision of marine and estuarine populatins of the estuarine catfish Cnidoglanis macrocephalus (Plotosidae) in southwestern Australia. Marine Biology 118: 25–31
  2. Chuwen, BM, Potter, IC, Hall, NG, Hoeksema, SD and Laurenson, LJB 2011, Changes in catch rates and length and age at maturity, but not growth, of an estuarine plotosid (Cnidoglanis macrocephalus) after heavy fishing. Fishery Bulletin, 109(3): 247-260
  3. Department of Fisheries 2015, Finfish Resources of the Peel-Harvey Estuary Harvest Strategy 2015–2020. Version 1.0. West Coast Estuarine Managed Fishery (Area 2). May 2015. Fisheries Management Paper No. 274. Department of Fisheries, Western Australia. 28pp.
  4. Kowarsky, J 1975, An ecological study of the estuarine catfish, Cnidoglanis macrocephalus. Ph.D. thesis. University of Western Australia, Nedlands, WA.
  5. Murphy, J.J., Ochwada-Doyle, F.A., West, L.D., Stark, K.E. and Hughes, J.M., 2020. The NSW Recreational Fisheries Monitoring Program - survey of recreational fishing, 2017/18. NSW DPI - Fisheries Final Report Series No. 158.
  6. Ryan, KL, Hall, NG, Lai, EK, Smallwood, CB, 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, Western Australia.
  7. Smith, K, Holtz, M, Bunbury, E, O'Malley, J and Yerman, M 2018, West Coast Nearshore and Estuarine Finfish Resource Status Report 2017 In: Status Reports of the Fisheries and Aquatic Resources of Western Australia 2016/17: The State of the Fisheries eds. D.J. Gaughan and K. Santoro. Department of Primary Industries and Regional Development, Western Australia. pp. 50–56.
  8. West, LD, Stark, KE, Murphy, JJ, Lyle, JM and Ochwada-Doyle, FA 2015, Survey of recreational fishing in New South Wales and the ACT, 2013–14, Fisheries Final Report Series 149, NSW Department of Primary Industries, Sydney.

Downloadable reports

Click the links below to view reports from other years for this fish.