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Australian Bonito (2023)

Sarda australis

  • John Stewart (New South Wales Department of Primary Industries)
  • Steph Blake (Australian Bureau of Agricultural and Resource Economics and Sciences)
  • Marlee Jesson-Kerr (Department of Agriculture and Fisheries, Queensland)

Date Published: June 2023

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Summary

Australian Bonito are a highly mobile species found in the western Pacific Ocean around south-eastern Australia, Norfolk Island and northern New Zealand. The Eastern Australia biological stock is classified as sustainable.

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Stock Status Overview

Stock status determination
Jurisdiction Stock Stock status Indicators
New South Wales Eastern Australia Sustainable

Depletion estimates, Catch, Catch rates, Size composition, Mortality rates

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Stock Structure

Australian Bonito Sarda australis occurs in the western Pacific Ocean where it is restricted to waters around south-eastern Australia, Norfolk Island and northern New Zealand [Collette and Nauen 1983]. Australian Bonito range from south-eastern Queensland southwards to northern Victoria. Little is known about stock structure within this range; however Australian Bonito are highly mobile and commercial landings exhibit consistent seasonal patterns in availability in terms of both abundance (peaking during summer and autumn) and sizes [Stewart et al. 2013].  Due to the latitudinal distribution along eastern-Australia, and influence of the prevailing southerly flowing Eastern Australian Current in this area, Australian Bonito are considered a single biological stock in this region.  Here, assessment of stock status is presented at the biological stock level—Eastern Australia.

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Stock Status

Eastern Australia

The Eastern Australia biological stock has components in Commonwealth, Queensland and New South Wales waters off eastern Australia. The catch of Australian Bonito by Commonwealth fishers is extremely low, averaging less than 200 kg per financial year since 2012–13. Australian Bonito in Queensland is managed under the East Coast Inshore Fishery Harvest Strategy [QDAF 2022]. Nominal commercial catch in Queensland peaked at 52 t in 2006–2007, dropping to an average of 12 t from 2012–2021. In 2021–22, commercial catch decreased further to 2 t. A similar pattern is observed in nominal effort in Queensland, suggesting the decrease in catch is associated with fisher behaviour rather than a decrease in biomass. Nominal effort (fishing days per year) averaged 317 from the period 2012–2021 and decreased to 52 days in 2021–22. Catch in the Queensland recreational sector is unknown, although it is likely to be low. Together, Commonwealth and Queensland fisheries have contributed less than 1% of the total annual harvest since 2012–13 and are considered minor components of this stock. Consequently, the stock is assessed using data from New South Wales.

Results from surplus production modelling using NSW commercial catch data from 1990–91 to 2021–22 and standardized catch rates from 1997–98 to 2021–22 produced imprecise estimates of depletion; however even the lowest trajectories during the time period remained above the limit reference level of 0.2 of the unfished biomass [Stewart 2023]. The median depletion level in 2021–22 was estimated to be 0.53 (CIs 0.28 to 0.88) which is well above the limit reference level of 0.2. Standardized catch rates for line fishing methods between 1997–98 and 2021–22 fluctuated substantially, likely a reflection of highly variable abundance of Australian Bonito as a result of their life history traits including extremely fast growth, early maturation, high mobility and variable recruitment [Stewart et al. 2013].  The absence of obvious overall trends in catch rates suggest that the biomass is not declining [Stewart 2023]. The above evidence indicates that the biomass of this stock is unlikely to be depleted and that recruitment is unlikely to be impaired.

Estimated Fishing mortality (F) from surplus production modelling was below that required to achieve maximum sustainable yield (MSY) with a high degree of certainty (Stewart 2023]. Fishing is therefore unlikely to cause the stock to decline [Stewart 2023]. Landed commercial catch during the late 2000s and early 2010s approached 350 t per year and exceeded the estimated MSY of approximately 200 t per year.  Catch in recent years has been well below the estimated MSY and fishing effort on Australian Bonito has been relatively stable with slight recent declines during the previous decade [Stewart 2023]. A change in length compositions from being bimodal during the 2000s to mainly the smaller mode from around 2010–11 onwards is potentially concerning and may indicate either a greater abundance of younger cohorts in more recent years, or alternatively excessive fishing of larger fish during the preceding high catch years. Given that these ‘bi-modal’ length composition years were generally lower catch years, and that the recent years of higher landings were associated with mainly the smaller mode of fish, the former hypothesis is most likely. Estimates of mortality derived from length-based catch curves and an estimated maximum age of 4 years indicate that total mortality (Z) is unlikely to exceed 2 x natural mortality (M) with a high degree of certainty [Stewart 2023]. 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 entire Eastern Australian biological stock is classified as a sustainable stock.

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Biology

Australian Bonito biology [Collette and Nauen 1983; Stewart et al. 2013]

Biology
Species Longevity / Maximum Size Maturity (50 per cent)
Australian Bonito

4 years, 1,000 mm FL

1 year, 360 mm FL

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Distributions

Distribution of reported commercial catch of Australian Bonito

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Tables

Fishing methods
New South Wales
Commercial
Hook and Line
Pole and Line
Trolling
Various
Indigenous
Spearfishing
Handline
Recreational
Spearfishing
Handline
Charter
Handline
Management methods
Method New South Wales
Commercial
Gear restrictions
Licence
Marine park closures
Spatial closures
Vessel restrictions
Indigenous
Customary fishing management arrangements
Recreational
Bag limits
Gear restrictions
Licence
Marine park closures
Possession limit
Spatial closures
Catch
New South Wales
Commercial 136.07t
Indigenous Unknown
Recreational approximately 7,000 fish (2019–20)

Commonwealth – Commercial (Management Methods/Catch). Data provided for the Commonwealth align with the 2021–22 financial year.

Commonwealth – Recreational. The Commonwealth does not manage recreational fishing in Commonwealth waters. Recreational fishing in Commonwealth waters is managed by the state or territory immediately adjacent to those waters under its management regulations. 

Commonwealth – Indigenous. The Australian government does not manage non-commercial Indigenous fishing in Commonwealth waters, with the exception of Torres Strait. In general, non-commercial Indigenous fishing in Commonwealth waters is managed by the state or territory immediately adjacent to those waters.

New South Wales – Recreational (Catch). Murphy et al. [2022].

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

Queensland – Recreational Fishing (Catch). Data with high uncertainty (Residual Error >50 %) have been excluded and listed as unknown. More information available at: https://www.daf.qld.gov.au/business-priorities/fisheries/monitoring-research/monitoring-reporting/statewide-recreational-fishing-surveys  

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

Queensland – Commercial (Catch). Queenslandcommercial and charter data have been sourced from the commercial fisheries logbook program. Further information available through the Queensland Fisheries Summary Report at: 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 Australian Bonito - note confidential catch not shown

Downloadable reports

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