*

Yellowfin Whiting is found in the coastal waters of south-western Australia. There are two stocks in WA and two in SA. All are assessed as sustainable.

Yellowfin Whiting is endemic to south-western Australia, being found in coastal waters from Exmouth in Western Australia to the gulf waters of South Australia [Gomon et al. 2008]. There is some uncertainty about the continuity of the species' distribution through the remote coastal waters between Western Australia and South Australia. Based on this possible discontinuous distribution, there is a possibility of separate stocks in these areas [Steer et al. 2018]. Western Australian populations in northern (Gascoyne Coast Bioregion) and southern (West Coast and South Coast Bioregions) regions also appear to have low connectivity. Adults in northern and southern regions have distinctly different size-at-age due to different growth rates, which suggests low levels of movement among regions [DPIRD unpublished data]. Northern and southern regions are therefore assumed to support separate biological stocks. In South Australia, oceanographic separation of the two gulfs during the spawning season in summer must considerably reduce the opportunity for mixing of eggs and larvae. As such, the populations in the gulfs may constitute separate stocks, but more evidence is required to confirm this.

Here, assessment of stock status is presented at the biological stock level—Northern Western Australia, Southern Western Australia, Spencer Gulf (South Australia) and Gulf St. Vincent (South Australia).

Northern Western Australia

A recent stock assessment (unpublished report) has been conducted for Yellowfin Whiting in the Gascoyne Coast Bioregion (GCB) using state space biomass dynamics models (JABBA, SPiCT) fitted to annual catch (1956–2022) and standardised catch per unit effort data (CPUE; 1976–2022) to estimate biomass (B) and fishing mortality (F). Both biomass dynamics models yielded similar results indicating that Yellowfin Whiting in northern Western Australia has recovered from early historical overfishing, with current biomass above B_MSY, and associated estimates of fishing mortality remaining below F_MSY since the early 1960s. Since that time, catches have typically remained below model estimates for maximum sustainable yield (MSY). The above results are supported by an abundance-maximum sustainable yield (AMSY) analysis, a recently-developed stock assessment approach requiring only a spawning stock abundance index [Froese et al. 2020]. AMSY was applied to standardised CPUE data (1976–2022) and yielded results consistent with outputs for F and relative biomass from the two biomass dynamics models. A further data-limited assessment analysis (catch-MSY) yielded a prediction for MSY that was similar to those from the two biomass dynamics models. The results from all four dynamic models are consistent with the conclusion of Smith et al. [2019] from their analysis of commercial fishery trends for Yellowfin Whiting in Shark Bay that, apart from a period of overfishing in the early 1960s, there is no evidence of major changes in abundance. A previous (equilibrium) per recruit model analysis, based on mortality estimates from catch curve analysis applied to commercial age composition data from 2014 [Brown 2014] estimated spawning potential ratio above the target (0.4) and relative biomass between the target and threshold (0.3). The results from this historic assessment indicate that, in 2014, the stock was being fished sustainability, which is consistent with outputs from the above dynamic assessment models. 

The commercial catch in the GCB in 2022 was 96 t with the estimated boat-based recreational catch less than 1 t. While there are no formal catch limits in place, catches in recent years have remained stable within the historic range of 70–230 t. The above evidence indicates that the biomass of this stock is unlikely to be depleted and that recruitment is unlikely to be impaired. Furthermore, 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 Northern Western Australia stock is classified as a sustainable stock. 

Southern Western Australia

A per recruit model, based on mortality estimates from a catch curve analysis applied to commercial age composition data from 2015–2016 [Duffy et al. 2022], estimated female spawning potential ratio (SPR) above the target (0.4). The results from this assessment indicate that the stock was being fished sustainably in 2015–16. The maximum age of fish sampled in 2015–16 was 11 years, which is close to the maximum recorded age for Yellowfin Whiting in southern Western Australia of 12 years. From an analysis of commercial catch per unit effort (CPUE) trends for Yellowfin Whiting throughout different areas of its distribution in Western Australia, Smith et al. [2019] concluded that its abundance in southern Western Australia towards the northern extent of this region (and thus, for example, in the Peel-Harvey Estuary, Swan Canning Estuary and adjacent ocean waters) has increased gradually in recent years. On the south coast of the state, the abundances of this species have increased more substantially (e.g., in Hardy Inlet and Irwin Inlet) [Smith et al. 2019]. The study concluded that these trends reflect a multi-decadal poleward shift in the geographic centre of the abundance of this species, associated with warming trends in coastal waters. 

Despite increasing commercial CPUE trends, commercial catches of Yellowfin Whiting in recent years (average of approximately 27 t in 2018–2022 for West and South Coast Bioregions combined) are lower than for some earlier periods (i.e., greater than 60 t in several years during the mid-1970s-1980s, and in 2000–2001). The recreational catch of Yellowfin Whiting is estimated from annual shore-based surveys of the Perth Metropolitan area (within the West Coast Bioregion) [Tate et al., 2022] and statewide boat-based surveys every 2–3 years [Ryan et al. 2022]. In 2021–22, the shore-based recreational catch of all whiting species combined in the Perth Metropolitan area was 0.6 t (95% CI; 0–1 t) [Tate et al. 2022]. In 2020–21, the boat-based recreational catch of Yellowfin Whiting was 6.3 t (95% CI; 2.6–8.9 t) for the West Coast Bioregion and 0.9 t (95% CI; 0.1–1.7 t) for the South Coast Bioregion (DPIRD unpublished data). As statewide shore-based catches are unknown, recreational catches of nearshore species will be underestimated from the statewide survey, particularly for species harvested in high proportions by shore-based recreational fishers. However, known recreational catches are low relative to commercial catches. The above evidence indicates that the biomass of this stock is unlikely to be depleted and that recruitment is unlikely to be impaired. Furthermore, 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 Southern Western Australia stock is classified as a sustainable stock.

Yellowfin Whiting biology [Ferguson 2000; Hutchins and Swainston 1986; Hyndes and Potter 1997]

Distribution of reported commercial catch of Yellowfin Whiting

Western Australia – Recreational (Catch). Recreational catches of Yellowfin Whiting are taken by shore-based fishers. The current recreational catch is unknown due to the absence of any recent surveys of shore-based fishing.

Commercial catch of Yellowfin Whiting - note confidential catch not shown

1. Beckmann, CL, Durante, LM, Graba-Landry, A, Stark, KE, and Tracey, SR 2023, Survey of recreational fishing in South Australia 2021–22, Report to PIRSA Fisheries and Aquaculture, South Australian Research and Development Institute (Aquatic Sciences), Adelaide, SARDI Publication No. F2022/000385-1. SARDI Research Report Series No. 1161. 185pp.
2. Brown, J 2014, Shark Bay Beach Seine and Mesh Net Managed Fishery Stock Status Report, December 2014, Unpublished report, Department of Fisheries, Western Australia. 19pp.
3. Duffy, R, Harris, D, Fisher, E, Smith, K, Johnston, D, Denham, A, Hesp, SA, Hodgson, B, Quinn, A and Newman, M 2022, South-West Estuarine and Nearshore Finfish Resource Part 1: Sea Mullet and Yellowfin Whiting, Fisheries Research Report No. 322, Department of Primary Industries and Regional Development, Western Australia. 142pp.
4. Ferguson, G 2000, Yellowfin whiting (Sillago schomburgkii), South Australian Fisheries Assessment Series 00/10.
5. Froese, R, Winker, H, Coro, G, Demirel, N, Tsikliras, AC, Dimarchopoulou, D, Scarcella, G, Palomares, MLD, Dureuil, M and Pauly, D 2020, Estimating stock status from relative abundance and resilience. ICES Journal of Marine Science, 77: 527–538.
6. Giri, K and Hall, K 2015, South Australian Recreational Fishing Survey. Fisheries Victoria Internal Report Series No. 62. 
7. Gomon, M, Bray, D and Kuiter, R 2008, Fishes of Australia's Southern Coast. New Holland Publishers (Australia) Pty Ltd, 928pp.
8. Hutchins, B and Swainston, R 1986, Sea fishes of southern Australia: complete field guide for anglers and divers, Swainston Publishing, Perth.
9. Hyndes, GA and Potter, IC 1997, Age, growth and reproduction of Sillago schomburgkii in south-western Australian, nearshore waters and comparisons of life history styles of a suite of Sillago species, Environmental Biology of Fishes 49: 435–447.
10. 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.
11. Smart, JJ, McGarvey, R, Feenstra, J, Drew, MJ, Earl, J, Durante, L, Beckmann, CL, Matthews, D, Matthews, JM, Mark, K, Bussell, J, Davey, J, Tsolos, A and Noell, C 2022, Assessment of the South Australian Marine Scalefish Fishery in 2021/22, Report to PIRSA Fisheries and Aquaculture, SARDI Publication No. F2017/000427-5, SARDI Research Report Series No. 1162. 308 pp.
12. Smith, KA, Dowling, CE and Brown, J 2019, Simmered then boiled: multi-decadal poleward shift in distribution by a temperate fish accelerates during marine heatwave. Frontiers of Marine Science. 6, Article 407. doi: 10.3389/fmars.2019.00407.
13. Steer, MA, Fowler, AJ, McGarvey, R, Feenstra, J, Westlake, EL, Matthews, D, Drew, M, Rogers, PJ and Earl, J 2018, Assessment of the South Australian Marine Scalefish Fishery in 2016, Report to PIRSA Fisheries and Aquaculture, South Australian Research and Development Institute (Aquatic Sciences), SARDI Publication No. F2017/000427-1, SARDI Research Report Series No. 974. 250pp.
14. Tate, AC. Rudd, LJ and Smallwood, CB 2022, Shore-based recreational fishing in the Perth Metropolitan area: 2022. Fisheries Research Report No. 326 Department of Primary Industries and Regional Development, Western Australia. 53pp.