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MORETON BAY BUGS (2023)

Thenus parindicus, Thenus australiensis, Thenus spp.

  • Matthew McMillan (Department of Agriculture and Fisheries, Queensland)
  • Krystle Keller (Australian Bureau of Agricultural and Resource Economics and Sciences)
  • Inigo Koefoed (Department of Primary Industries and Regional Development, Western Australia)

Date Published: June 2023

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Summary

Reef Bug and Mud Bug, collectively known as Moreton Bay Bugs, are sustainable species distributed along the tropical and subtropical coast of Australia.

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Stock Status Overview

Stock status determination
Jurisdiction Stock Stock status Indicators
Western Australia Western Australia Sustainable

Catch

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Stock Structure

Reef Bug (Thenus australiensis) and Mud Bug (Thenus parindicus) are known collectively as ‘Moreton Bay Bugs’. Moreton Bay Bugs are distributed along the tropical and subtropical coast of Australia from northern New South Wales to Shark Bay in Western Australia [George and Griffin 1972]. The two species have overlapping distributions but display relatively strong habitat partitioning. Reef Bugs typically prefer deeper areas with coarser sediments, while Mud Bugs inhabit mainly shallow inshore areas with finer sediments [McMillan et al. 2023]. In the Queensland East Coast Otter Trawl Fishery (ECOTF), where around 80% of total landings occur, the two species have been differentiated in the catch since 2021. Modelling of species distributions combined with harvest locations indicated that the proportion of Reef Bugs comprising total landings increased from around 67% of landings in the ECOTF in 1988 (at the beginning of logbook records) to 93% in 2021 [McMillan et al. 2023]. This reflects a shift to targeted fishing for the larger, more valuable Reef Bugs, while Mud Bugs remain an incidentally caught species in the ECOTF. In other fisheries, both species are undifferentiated in the catch and are assessed together. Genetic population structure of Reef Bugs, which dominate landings in the ECOTF, supportsa single biological stock on Queensland’s east coast [McMillan et al. 2024]. No studies have been carried out on the biological stock structure of Moreton Bay Bugs in other fisheries.

Given the uncertainty in biological stock structure, here assessment of stock status is presented at the management unit level—Northern Prawn Fishery (Commonwealth), Torres Strait Prawn Fishery (Commonwealth) and East Coast Otter Trawl Fishery (Queensland); and the jurisdictional level—Western Australia.

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Stock Status

Western Australia

No formal stock assessment exists for Moreton Bay Bugs in Western Australia. Moreton Bay Bugs are not targeted in Western Australia but are landed occasionally as a by-product species of prawn and scallop trawl fisheries, so directed fishing effort is low. In 2022, the combined Western Australian fisheries landings of Moreton Bay Bugs was 6 t, which is low but within the historical catch range. Combined fishery landings have been at or below 10 t in nine out of the last 10 years. The spatial coverage of Western Australian fisheries that retain Moreton Bay Bugs is limited compared with the large area across which Moreton Bay Bugs are distributed in north-western Western Australia. Substantial Moreton Bay Bug biomass is protected within the extensive network of fishery closures in place from Shark Bay to Napier Broome Bay [Newman et el. 2023]. The above evidence indicates that the biomass of this stock is unlikely to be depleted, and that 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 Australian jurisdictional stock is classified as a sustainable stock.

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Biology

Moreton Bay Bug biology [Courtney 1997; Jones 1988]

Biology
Species Longevity / Maximum Size Maturity (50 per cent)
MORETON BAY BUGS

7 years T. australiensis: Males 106 mm CW, Females 124 mm CW T. parindicus: Males 87 mm CW, Females 103 mm CW

T. australiensis: Female 82 mm CW T. parindicus: Female 75 mm CW

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Distributions

Distribution of reported commercial catch of Moreton Bay Bugs
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Tables

Fishing methods
Western Australia
Commercial
Otter Trawl
Indigenous
Unspecified
Recreational
Unspecified
Management methods
Method Western Australia
Commercial
Effort limits
Limited entry
Spatial closures
Vessel restrictions
Catch
Western Australia
Commercial 6.35t
Indigenous No catch
Recreational No catch

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

Commonwealth – Indigenous. The Australian government does not manage non-commercial Indigenous fishing (with the exception of the Torres Strait). In general, non-commercial Indigenous fishing in Commonwealth waters is managed by the states or territory immediately adjacent to those waters. In the Torres Strait, both commercial and non-commercial Indigenous fishing is managed by the Torres Strait Protected Zone Joint Authority (PZJA) through the Australian Fisheries Management Authority (Commonwealth), Department of Agriculture Fisheries and Forestry (Queensland) and the Torres Strait Regional Authority. The PZJA also manages non-Indigenous commercial fishing in the Torres Strait.

Commonwealth – Commercial (Management Methods/Catch). Data provided for the Commonwealth align with 202122 financial year.

Queensland – Indigenous (Management Methods). For more information see https://www.daf.qld.gov.au/business-priorities/fisheries/traditional-fishing

Queensland – Commercial (Catch) Commercial data have been sourced from the commercial fisheries logbook program. Further information available through the 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  

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Catch Chart

Commercial catch of MORETON BAY BUGS - note confidential catch not shown
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References

  1. Courtney, AJ 1997, A study of the biological parameters associated with yield optimisation of Moreton Bay Bugs, Thenus spp., final report (project 92/102), Queensland Department of Primary Industries, Brisbane.
  2. Courtney, AJ 2002, The status of Queensland’s Moreton Bay Bug (Thenus spp.) and Balmain Bug (Ibacus spp.) stocks, Queensland Government, Department of Primary Industries, Brisbane.
  3. Courtney, AJ, Campbell, MJ, Roy, DP, Tonks, ML, Chillcott, KE and Kyne, PM 2008, Round scallops and square meshes: a comparison of four codend types on the catch rates of target species and by-catch in the Queensland (Australia) saucer scallop (Amusium balloti) trawl fishery, Marine and Freshwater Research, 59: 849–864.
  4. George, RW and Griffin, DJG 1972, The shovel nosed lobsters of Australia, Australian Natural History, September 1972, 227–231.
  5. Griffiths, S, Kenyon, R, Bulman, C, Dowdney, J, Williams, A, Sporcic, M and Fuller, M 2007, Ecological risk assessment for the effects of fishing: report for the Northern Prawn Fishery, report for the Australian Fisheries Management Authority, Canberra.
  6. Helidoniotis, F 2020, Standardised catch rates for Queensland Moreton Bay bugs (Thenus spp.), Technical Report, Department of Agriculture and Fisheries, Brisbane.
  7. Hill, B, Blaber, S, Wassenberg, T, and Milton, D 1998, Composition and Fate of Discards, in I Poiner, J Glaister, R Pitcher, C Burridge, T Wassenberg, N Gribble, B Hill, S Blaber, D Milton, D Brewer, and N Ellis (eds), The Environmental Effects of Prawn Trawling in the Far Northern Section of the Great Barrier Reef Marine Park: 1991-1996, CSIRO Division of Marine Research, Cleveland.
  8. Jacobsen, I, Zeller, B, Dunning, M, Garland, A, Courtney T and Jebreen, E, An Ecological Risk Assessment of the Southern Queensland East Coast Otter Trawl Fishery and River and Inshore Beam Trawl Fishery, Fisheries Queensland, Department of Agriculture and Fisheries, Brisbane.
  9. Jones, CM 1988, The biology and behaviour of bay lobsters, Thenus spp. (Decapoda: Scyllaridae), in northern Queensland, Australia, PhD thesis, University of Queensland, Brisbane.
  10. McMillan, MN, Brunjes, N, Williams, SM, Holmes, BJ 2024, Broad-scale genetic population connectivity in the Moreton Bay Bug (Thenus australiensis) on Australia’s east coast. In Press.
  11. McMillan, NN, Leahy, SM, Daniell, J, Louw, N, Roberts, EM, Wickens, M, Hillcoat, K, and O’Neill, MF 2023, Determining the spatial distribution and abundance indices for Moreton Bay Bugs, Thenus parindicus and Thenus australiensis in Queensland to improve stock assessment and management. Fisheries Research and Development Corporation Project 2020/020 Final Report.
  12. Milton, DA, Fry, GC, Kuhnert, P, Tonks, M, Zhou, S and Zhu, M 2010, Assessing data poor resources: developing a management strategy for byproduct species in the Northern Prawn Fishery, final report to the Fisheries Research and Development Corporation, project 2006/008.
  13. Newman, S, J, Wise, B, S, Santoro, K, G, and Gaughan, D, J (eds) 2023, 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.
  14. Newman, SJ, Wise, BS, Santoro, KG, and Gaughan, DJ (eds) 2023, 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.
  15. Pears, RJ, Morison, AK, Jebreen, EJ, Dunning, M, Pitcher, CR, Courtney, AJ, Houlden, B and Jacobsen, IP 2012, Ecological risk assessment of the East Coast Otter Trawl Fishery in the Great Barrier Reef Marine Park: Technical Report, Great Barrier Reef Marine Park Authority, Townsville.
  16. Pitcher, CR, Doherty, P, Arnold, P, Hooper, J, Gribble, N, Bartlett, C, Browne, M, Campbell, N, Cannard, T, Cappo, M, Carini, G, Chalmers, S, Cheers, S, Chetwynd, D, Colefax, A, Coles, R, Cook, S, Davie, P, De’ath, G, Devereux, D, Done, B, Donovan, T, Ehrke, B, Ellis, N, Ericson, G, Fellegara, I, Forcey, K, Furey, M, Gledhill, D, Good, N, Gordon, S, Haywood, M, Jacobsen, I, Johnson, J, Jones, M, Kinninmoth, S, Kistle, S, Last, P, Leite, A, Marks, S, McLeod, I, Ozkowicz, S, Rose, C, Seabright, D, Sheils, J, Sherlock, M, Skelton, P, Smith, D, Smith, G, Speare, P, Stowar, M, Strickland, C, Sutcliffe, P, Van der Geest, C, Venables, W, Walsh, C, Wassenberg, T, Welna, A, and Yearsley, G 2007, Seabed biodiversity on the continental shelf of the Great Barrier Reef World Heritage Area, AIMS/CSIRO/QM/QDPI CRC Reef Research Task final report.
  17. Pitcher, CR, Haywood, M, Hooper, J, Coles, R, Bartlett, C, Browne, M, Cannard, T, Carini, G, Carter, A, Cheers, S, Chetwynd, D, Colefax, A, Cook, S, Davie, P, Ellis, N, Fellegara, I, Forcey, K, Furey, M, Gledhill, D, Hendriks, P, Jacobsen, I, Johnson, J, Jones, M, Last, P, Marks, S, McLeod, I, Sheils, J, Sheppard, J, Smith, G, Strickland, C, Van der Geest, C, Venables, W, Wassenberg, T and Yearsley, G 2007, Mapping and characterisation of the biotic and physical attributes of the Torres Strait ecosystem, CSIRO/QM/QDPI CRC Torres Strait Task final report.
  18. Turnbull, C and Rose, CL 2007, Towards ecologically sustainable management of the Torres Strait Prawn Fishery, CRC Torres Strait Task T1.5 final report, Department of Primary Industries and Fisheries, Queensland.
  19. Wickens, ME, Hillcoat, KB, Lovett, RA, Fox, AR, and McMillan MN 2023 Stock assessment of Moreton Bay bugs (Thenus australiensis and Thenus parindicus) in Queensland, Australia with data to December 2021. Final Report, Queensland Department of Agriculture and Fisheries, Brisbane.
  20. Zeller, B, Kangas, M, and Larcombe, J, 2014, Moreton Bay Bug Thenus australiensis, T. parindicus, in M Flood, I Stobutzki, J Andrews, C Ashby, G Begg, R Fletcher, C Gardner, L Georgeson, S Hansen, K Hartmann, P Hone, P Horvat, L Maloney, B McDonald, A Moore, A Roelofs, K Sainsbury, T Saunders, T Smith, C Stewardson, J Stewart and B Wise (eds) 2014, Status of key Australian fish stocks reports 2014, Fisheries Research and Development Corporation, Canberra.

Downloadable reports

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