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Estuary Cobbler (2018)

Cnidoglanis macrocephalus

  • Rodney Duffy (Department of Primary Industries and Regional Development, Western Australia)
  • Amy Smoothey (Department of Primary Industries, New South Wales)

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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 Fisheries Stock status Indicators
New South Wales New South Wales Estuary General EGF Undefined
EGF
Estuary General Fishery (NSW)
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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 between estuarine 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 Fishery 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 six and 20 t per annum with the majority caught using mesh nets. In the Estuary General Fishery, Estuary Cobbler is taken largely as by-catch or by-product. Similar to Western Australia, a small number of estuaries account for the majority of the catch of Estuary Cobbler with the most taken from the Clarence River (42 per cent of catch in 2017). During the past five years, catches have consistently been stable between 13 and 17 t, but declined to 6 t in 2017. This harvest reduction was likely associated with reduced fishing effort as a result of the commercial fisheries consolidation. 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].  Currently there is insufficient information available to assess the likely biomass size or the adequacy of controls over fishing pressure on the stock.

On the basis of the evidence provided above, Estuary Cobbler stock 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
Unspecified
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
Bag limits
Native Title
Section 37 (1d)(3)(9), Aboriginal cultural fishing authority
Recreational
Bag limits
Gear restrictions
Licence
Spatial zoning
Active vessels
New South Wales
51 in EGF
EGF
Estuary General Fishery (NSW)
Catch
New South Wales
Commercial 10.56t in EGF
Indigenous Unknown
Recreational Unknown
EGF
Estuary General Fishery (NSW)

Western Australia – Recreational (Management methods) In Western Australia a recreational fishing license is only required for fishing from a boat
NSW – Indigenous  (Management methods) (a) The Aboriginal Cultural Fishing Interim Access Arrangement allows an Indigenous fisher in New South Wales to take in excess of a recreational bag limit in certain circumstances—for example, if they are doing so to provide fish to other community members who cannot harvest themselves; (b) The Aboriginal cultural fishing authority is the authority that Indigenous persons can apply to take catches outside the recreational limits under the Fisheries Management Act 1994 (NSW), Section 37 (1d)(3)(9), Aboriginal cultural fishing authority; and  (c) In cases where the Native Title Act 1993 (Cth) applies fishing activity can be undertaken by the person holding native title in line with S.211 of that Act, which provides for fishing activities for the purpose of satisfying their personal, domestic or non-commercial communal needs. In managing the resource where native title has been formally recognised, the native title holders are engaged with to ensure their native title rights are respected and inform management of the State's fisheries resources.

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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. 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. Kowarsky, J 1975, An ecological study of the estuarine catfish, Cnidoglanis macrocephalus. Ph.D. thesis. University of Western Australia, Nedlands, WA.
  6. Martell, S and Froese R 2013, A simple method for estimating MSY from catch and resilience. Fish and Fisheries 14: 504-514.
  7. Ryan, KL, Hall, NG, Lai, EK, Smallwood, CB, Taylor, SM and Wise, BS 2017, Statewide survey of boat-based recreational fishing in Western Australia 2015/16. Fisheries Research Report No. 287, Department of Primary Industries and Regional Development, Western Australia.
  8. 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.
  9. 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.