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Estuary Cobbler (2023)

Cnidoglanis macrocephalus

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

Date Published: June 2023

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Summary

WA has two sustainable stocks of Estuary Cobbler. The 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

There is a single species of Estuary Cobbler in Australia (Cnidoglanis macrocephalus). The species occurs across the southern half of Australia in estuaries, embayments and marine environments [Kowarsky 1975; Lenanton and Potter 1987]. Most of the commercial catch, however, is taken in estuarine waters [Duffy et al. 2023a,b; Smith and Lenanton 2021]. Evidence from Western Australia indicates that there are genetic differences between estuarine populations and adjacent marine populations [Ayvazian et al. 1994]. There is no information on the species' stock structure in eastern Australia, although it is likely to be complex with multiple separate biological stocks.

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

During the past 10 years, commercial catches from the Estuary General Fishery have gradually decreased from 17.6 tonnes (t) in 2014 to 7.9 t in 2022. Declines in landings coincide with large reductions in total report fishing effort from the Estuary General mesh net fishery. However, between 2020 and 2022, catches have been stable between 9.5 and 7.9 t. The majority are caught using mesh nets and 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. 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, the New South Wales Estuary General management unit is classified as an undefined stock.

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Biology

Estuary Cobbler biology [Chuwen et al. 2011; Gray 2022]

Biology
Species Longevity / Maximum Size Maturity (50 per cent)
Estuary Cobbler

20 years [New South Wales], 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
Haul Seine
Otter Trawl
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 7.62t
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. [2022].

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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 populations 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. Duffy, D, Harris, B, Brooks, Blazeski, S and Quinn, A 2023, South Coast Estuarine And Nearshore Scalefish And Invertebrate Resource Status Report 2022. In SJ Newman, BS Wise, KG Santoro and DJ Gaughan (ed.s), Status Reports of the Fisheries and Aquatic Resources of Western Australia 2021/22: The State of the Fisheries, Department of Primary Industries and Regional Development, Western Australia. pp. 213-221
  4. Duffy, R, Quinn, A, Brooks, B and Blazeski, S 2023, West Coast Nearshore And Estuarine Finfish Resource Status Report 2022. In SJ Newman, BS Wise, KG Santoro and DJ Gaughan (ed.s), Status Reports of the Fisheries and Aquatic Resources of Western Australia 2021/22: The State of the Fisheries, Department of Primary Industries and Regional Development, Western Australia. pp. 63-70
  5. Gray, CA 2022, Life history characteristics of the estuary eeltail catfish Cnidoglanis macrocephalus (Plotosidae) in eastern Australia. Ichthyol Res 69, 267–274 (2022). https://doi.org/10.1007/s10228-021-00836-z
  6. Kowarsky, J 1975, An ecological study of the estuarine catfish, Cnidoglanis macrocephalus. Ph.D. thesis. University of Western Australia, Nedlands, WA.
  7. Lenanton, RCJ & Potter, IC 1987, Contribution of estuaries to commercial fisheries in temperate Western Australia and the concept of estuarine dependence. Estuaries 1987 10:1, 10(1), 28–35.
  8. Murphy, JJ, Ochwada-Doyle, FA, West, LD, Stark, KE and Hughes, JM, Taylor, MD 2022, Survey of recreational fishing in NSW, 2019/20. NSW DPI - Fisheries Final Report Series No. 161.
  9. Ryan KL, Lai, EKM and Smallwood, CB 2022, Boat-based recreational fishing in Western Australia 2020/21. Fisheries Research Report No. 327 Department of Primary Industries and Regional Development, Western Australia. 221pp
  10. Smith, KA and Lenanton, RCJ 2021, Almost forgotten: Historical abundance of eel-tail catfish populations in south-western Australian estuaries and their decline due to habitat loss and historical overfishing. Regional Studies in Marine Science, 41, 101605.
  11. 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.