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Saddletail Snapper are widely distributed throughout the Indo-West Pacific region. Genetic studies identified three broad biological stocks across northern Australia [Elliot 1996, Salini et al. 2006], but more recent research using otolith microchemistry and parasites has identified discrete biological stocks in the Joseph Bonaparte Gulf, Timor and Arafura Seas, and the Gulf of Carpentaria. This assessment is therefore presented at the biological stock level. All stocks are classified as sustainable. 

Saddletail Snapper is a widespread Indo-Pacific species found from Shark Bay in Western Australia, across northern Australia to the east coast of Queensland [Newman 2002]. Genetic studies indicate that three biological stocks occur across the species' Australian range: the North Coast Bioregion biological stock, the Northern Australian biological stock (including the Timor Sea, Arafura Sea and the Gulf of Carpentaria) and the East coast of Queensland biological stock [Elliot 1996; Salini et al. 2006]. Saunders et al. [2018] used otolith microchemistry and parasitology to identify separate biological Saddletail Snapper stocks in the Joseph Bonaparte Gulf, Timor and Arafura seas and Gulf of Carpentaria.

Here, assessments of stock status are presented at the 5 identified biological stock level—North Coast Bioregion (Western Australia), Joseph Bonaparte Gulf (Northern Territory), Timor-Arafura seas (Northern Territory), Gulf of Carpentaria (Northern Territory and Queensland) and East coast (Queensland).

Gulf of Carpentaria

The Gulf of Carpentaria Saddletail Snapper stock is mainly harvested by commercial finfish trawl operators within the Gulf of Carpentaria Developmental Fin Fish Trawl Fishery) (GOCDFFTF - Queensland) and Demersal Fishery (DF- Northern Territory). Recreational and Indigenous harvest of Saddletail Snapper is low given the offshore distribution of this species [QDAF 2023], and charter catches have been <1 t. Saddletail Snapper were also exposed to fishing from foreign fleets during the 1950s to the 1980s [O’Neill et al. 2011], but these catches (annual peak of 261 t) were substantially lower than contemporary levels. 

In the Queensland portion of this stock, commercial catches were very low (average < 4 t) until they increased substantially during 2002–13 (average 135 t). Fish trawl effort and catch from the GOCDFFTF declined markedly after 2011–12 as a result of trawl effort being transferred to other stocks. A revised total quota tonnage for all species of 450 t for the fishery introduced in 2015 represented a considerable reduction from the 1,250 t set in previous years [O’Neil et al. 2011; Leigh and O’Neill 2016]. There was no catch of Saddletail Snapper by this fishery from 2016–17 to 2019–20. With renewed interest in the fishery, commercial fishing resumed from 2020–21 with a catch of 49 t and 42 t the next year. These catch totals are well below the 150 t Saddletail Snapper TACC set for the fishery. Fishery independent surveys in 2021 provided updated estimates of relative biomass for the fishery [Knuckey et al. 2022] but no changes to management of the fishery have occurred. However, in the Northern Territory portion of this stock, an increase in the targeting of this species by the DF in 2019-20 led to a very large increase in catch (728 t). After this peak, catches reduced to quantities similar to the ten-year average in this stock (257 t), with 247 t caught in 2020–21 and 232 t caught in 2021–22.

This stock has been assessed using data up to 2022 using a catch-MSY model, incorporating catch data from both Queensland and the Northern Territory. It is important to recognise that catch-MSY is a data-limited technique with strong assumptions, dependent on user inputs. The results of this modelling were that biomass was estimated to be between 29% and 57% of unfished levels, which is above the limit reference point. This indicates that the biomass of this stock is unlikely to be depleted and that recruitment is unlikely to be impaired. However, the biomass trajectory shows that the stock continues to decline since 2007, although not at levels sufficient to classify the stock as depleted [Pazhayamadom 2023]. The high levels of exploitation predicted by the model is probably an artefact of relatively low historical catches, which do not represent the large biomass present and consequently bias F upwards and depletion downwards [Saunders and Roelofs 2020]. Nevertheless, subsequent years will require close monitoring to ensure that the model bias is in fact true and unsustainable fishing pressure is not being exerted.  

A trawl survey conducted in 1990 predicted that the biomass of Saddletail Snapper in this stock was approximately 14,000 t [Sainsbury et al. 1991], with more recent biomass surveys also indicating there is a large stock size in the Gulf of Carpentaria, estimating the biomass of the NT portion of the stock was around 70,000 t [Knuckey and Koopman 2022; Knuckey et al. 2022]. Taking the most conservative estimation of biomass, the peak catch in 2019-20 only represents approximately a 6% harvest fraction. However, it should be noted that the most recent survey was designed to obtain a time-series of consistent and robust relative abundance indices and due to uncertainties around assumptions of catchability, herding and escapement, this one-off estimate of absolute abundance should be used with caution. Additionally, due to differences in survey design, biomass estimates between the 1990 and 2021 surveys should not be compared [Knuckey and Koopman 2022]. Regardless, these estimates of biomass can assist in understanding the impact fishing has on this stock, with the low level of catch relative to biomass size, along with the results of the catch-MSY modelling, indicating the level of fishing mortality is unlikely to cause the stock to become recruitment impaired. 

On the basis of the evidence provided above, the Gulf of Carpentaria (Northern Territory and Queensland) biological stock is classified as a 

sustainable stock.

Joseph Bonaparte Gulf

Harvest of this Saddletail Snapper stock was first reported in 1988 and the average catch from trap and line vessels in the Demersal Fishery (DF) to 2011 was very small (average < 2 t) compared to the adjacent Timor-Arafura seas stock. From 2011–12 a finfish trawler entered the fishery and catches increased to 180 t in the first year and have averaged 268 t over the last 10 years, with a maximum catch in 2018–19 (367 t) and a minimum catch in 2021–22 (95 t). A trawl survey conducted on this stock [Ramm 1994] suggested that the Saddletail Snapper biomass was relatively large (6,677 t). A more recent fishery independent survey supported this finding, estimating a stock size of 8,891 t [Knuckey and Koopman 2022]. Consequently, the peak harvest represents approximately a 5% harvest fraction of the most conservative estimate of biomass. It is important to note that this most recent survey was designed to obtain a time-series of consistent and robust relative abundance indices and due to uncertainties around assumptions of catchability, herding and escapement, this one-off estimate of absolute abundance should be used with caution. Additionally, due to differences in survey design, the biomass estimates from the two separate surveys should not be compared [Knuckey and Koopman 2022]. Regardless, these estimates of biomass can assist in understanding the impact fishing has on this stock, with the low level of catch relative to biomass size indicating the level of fishing mortality is unlikely to cause the stock to become recruitment impaired.

This stock was also assessed using data up to 2022 using a stochastic Stock Reduction Analysis (SRA) model. Biomass was estimated to be between 57% and 86% of unfished levels, which is above the limit reference point. The stock is not considered to be recruitment impaired. Exploitation values were also found to be below the reference point relative to MSY levels indicating the fishing pressure is at sustainable levels [Pazhayamadom 2023]. Overall, the SRA outputs indicate that the current fishing mortality is unlikely to cause to the stock to become recruitment impaired.

Based on the evidence above, the Joseph Bonaparte (Northern Territory) biological stock is classified as a sustainable stock.

Timor, Arafura seas

Saddletail Snapper was one of several tropical snapper species that were heavily exploited in this stock by foreign fishing operations from the early 1970s to 1990 [O’Neill et al. 2011]. Annual catches by this fleet peaked in the late 1980s at 2,189 t. Domestic harvest was negligible until 1995 when trawl operations began. Since 2012–13 catches from this stock have fluctuated between a maximum of 1,812 t in 2017-18 to a minimum of 979 t in 2019-20.

A fishery independent survey was undertaken in 2021 to estimate relative biomass of key offshore species in Northern Territory waters, including Saddletail Snapper. As a result of this work, biomass of Saddletail Snapper in the NT was estimated to be 165,707 t, with a coefficient of variation of 0.08. Within this, the biomass of Saddletail Snapper in the Timor, Arafura seas stock was estimated to be approximately 86,707 t [Knuckey and Koopman 2022]. The commercial harvest in this stock has averaged 1,418 t in the last 10 years, which is around 2% of the estimated relative biomass. It is important to note that this survey was designed to obtain a time-series of consistent and robust relative abundance indices and due to uncertainties around assumptions of catchability, herding and escapement, this one-off estimate of absolute abundance should be used with caution [Knuckey and Koopman 2022]. Regardless, this estimate of biomass can assist in understanding the impact fishing has on this stock, with the low level of catch relative to biomass size. 

This stock was also assessed using a stochastic Stock Reduction Analysis (SRA) model with data up to 2022. Biomass was estimated to be between 77% and 85% of unfished levels, which is above the limit reference point. The stock is not considered to be recruitment impaired. Exploitation values were also found to be below the reference point relative to MSY indicating the fishing pressure is at sustainable levels [Pazhayamadom 2023]. The results of this SRA assessment, along with the high biomass levels indicated by the fishery independent survey indicate that the current fishing mortality is unlikely to cause to the stock to become recruitment impaired.

On the basis of the evidence provided above, the Timor-Arafura seas (Northern Territory) biological stock is classified as a sustainable stock.

Saddletail Snapper biology [Fry and Milton 2009; Fry et al. 2009; McPherson et al. 1992; McPherson and Squire 1992; Carpenter and Niem 2001; Newman 2002; Newman et al. 2000]}

Western Australia – Active Vessels. Data is confidential as there were fewer than three vessels in Pilbara Fish Trawl Interim Managed Fishery and Pilbara Trap Managed Fishery.

Western Australia – Recreational (Catch). Boat-based recreational catch is from 1 September 2020–31 August 2021. These data are derived from those reported in [Ryan et al. 2022].

Western Australia – Recreational (Management Methods). A Recreational Fishing from Boat Licence is required for the use of a powered boat to fish or to transport catch or fishing gear to or from a land-based fishing location.

Western Australia – Indigenous (Management Methods Subject to application of Section 211 of the Native Title Act 1993 (Cth), and the exemption from a requirement to hold a recreational fishing licence, the non-commercial take by Indigenous fishers is covered by the same arrangements as that for recreational fishing.

Northern Territory – Recreational (Catch). Saddletail Snapper, Crimson Snapper and Indonesian Snapper catch were combined during the Northern Territory 2018 to 2019 recreational fishing survey. Saddletail Snapper was assumed to be a proportion of the total reported catch of these species [West et al. 2022].

Northern Territory – Charter (Management Methods). In the Northern Territory, charter operators are regulated through the same management methods as the recreational sector but are subject to additional limits on license and passenger numbers.

Northern Territory – Indigenous (Management Methods).The Fisheries Act 1988 (NT), specifies that: “Unless expressly provided otherwise, nothing in this Act derogates or limits the right of Aboriginal people who have traditionally used the resources of an area of land or water in a traditional manner to continue to use those resources in that area in that manner.”

Queensland – Commercial (Catch). Queensland commercial and charter data have been sourced from the commercial fisheries logbook program. Further information are available through the Queensland Fisheries Summary Report: https://www.daf.qld.gov.au/business-priorities/fisheries/monitoring-research/data/queensland-fisheries-summary-report 

Queensland – Recreational Fishing (Catch). Data based at the whole of Queensland level and are derived from statewide recreational fishing surveys. Estimates have been converted to weight (tonnes) using best known conversion multipliers. Conversion factors may display regional or temporal variability.   

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

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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