MORETON BAY BUGS (2023)
Thenus parindicus, Thenus australiensis, Thenus spp.
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.
Stock Status Overview
Jurisdiction | Stock | Stock status | Indicators |
---|---|---|---|
Queensland | East Coast Otter Trawl Fishery | Sustainable | Catch, CPUE |
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.
Stock Status
East Coast Otter Trawl Fishery
East Coast Otter Trawl Fishery (Queensland) (ECOTF) management unit, one fleet north of 22° S trawling for prawns and one fleet south of 22° S trawling for scallops. However, due to depletion of the Saucer Scallop stock and closure of that fishery since 2021 in the Hervey Bay-Gladstone region, the southern fleet has shifted to increased targeting of co-located Reef Bugs. Increasing market value has also seen a shift to periodic targeting of Reef Bugs by the northern fleet in waters of Townsville. These two areas (Hervey Bay-Gladstone and Townsville) contribute approximately 80% of Moreton Bay Bug landings in the ECOTF. The trend toward increased targeting of Reef Bugs is reflected in catch rate analyses [Helidoniotis 2020; McMillan et al. 2023]. Mud Bugs remain an incidentally caught species landed mostly by the northern fleet when targeting Tiger Prawns.
The first stock assessment of Moreton Bay Bugs in the ECOTF estimated that in 2021 the Reef Bug stock was at approximately 78% of unfished biomass. [Wickens et al. 2023]. The Mud Bug stock was not assessed due to uncertainties assessing non-target species. Standardised catch rates for Reef Bugs increased from 35 kg/day in 1988 (when logbook records began) to a peak of 46 kg/day in 2013 before stabilising to 36 kg/day by 2021 [McMillan et al. 2023]. Mud Bug catch rates followed a similar trend, increasing from 7 kg/day in 1988 to a peak of 11 kg/day in 2013 before stabilising to 7 kg/day in 2021 [McMillan et al. 2023]. Management measures leading to reduced overall fishing effort and a smaller fleet since the early 2000s as well as the closure of large areas to fishing within the Great Barrier Reef Marine Park (GBRMP) since 2004, where large spawning populations are now protected, are likely responsible for the similarity in catch rates between 1988 and 2021 despite increased targeted fishing for Reef Bugs.
Biophysical modelling estimated that in 2005 significant parts of the biomass (54 per cent of Reef Bugs; and 45 per cent of Mud Bugs) were within GBRMP trawl closures [Pitcher et al. 2007a]. It is likely that spawning adults in areas closed to fishing within the GBRMP contribute recruits to other areas open to trawling via pelagic larval dispersal, facilitated by the approximately 45-day pelagic larval phase of Moreton Bay Bugs [Jones 1988]. Ecological risk assessments have reported a low risk of the stock being recruitment overfished in the GBRMP [Pears et al. 2012], where harvesting pressure on the stock is greatest, and an intermediate risk of being classified as recruitment overfished south of the GBRMP [Jacobsen et al. 2018].
The number of days on which Moreton Bay Bugs were caught and the number of boats catching Moreton Bay Bugs declined between 2000 and 2014 before stabilising between 2015 and 2022. Relatively stable effort in high abundance grids since 2014 indicates that fishing mortality in high biomass areas has not increased substantially. Based on yield-per-recruit analysis, capture at ≥ 75 mm CW allows Moreton Bay Bugs to spawn before they enter the fishery [Courtney 1997]. Square-mesh cod end bycatch reduction devices (BRDs) were made mandatory in the Scallop Fishery in 2015, allowing juvenile Moreton Bay Bugs to escape trawl capture and reducing incidental fishing mortality [Courtney et al. 2008]. Moreton Bay Bugs are also known to survive discarding well [Hill et al. 1998]. The above evidence indicates 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 East Coast Otter Trawl Fishery (Queensland) management unit is classified as a sustainable stock.
Biology
Moreton Bay Bug biology [Courtney 1997; Jones 1988]
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 |
Tables
Queensland | |
---|---|
Commercial | |
Otter Trawl | |
Recreational | |
Diving | |
Traps and Pots |
Method | Queensland |
---|---|
Commercial | |
By-catch reduction devices | |
Effort limits (individual transferable effort) | |
Gear restrictions | |
Harvest Strategy | |
Limited entry | |
Processing restrictions | |
Seasonal or spatial closures | |
Size limits | |
Vessel restrictions | |
Recreational | |
Gear restrictions | |
Processing restrictions | |
Seasonal or spatial closures | |
Size limits |
Queensland | |
---|---|
Commercial | 281.24t |
Indigenous | No catch |
Recreational | Unknown |
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 2021–22 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
References
- 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.
- 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.
- 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.
- George, RW and Griffin, DJG 1972, The shovel nosed lobsters of Australia, Australian Natural History, September 1972, 227–231.
- 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.
- Helidoniotis, F 2020, Standardised catch rates for Queensland Moreton Bay bugs (Thenus spp.), Technical Report, Department of Agriculture and Fisheries, Brisbane.
- 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.
- 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.
- Jones, CM 1988, The biology and behaviour of bay lobsters, Thenus spp. (Decapoda: Scyllaridae), in northern Queensland, Australia, PhD thesis, University of Queensland, Brisbane.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.