Threatened Species Nomination 2020 Details of the nominated species or subspecies NAME OF SPECIES (OR SUBSPECIES) Scientific name: Dentiraja australis Common name(s): Sydney skate, Common skate TAXONOMY Provide any relevant detail on the species' taxonomy (e.g. authors of taxon or naming authority, year and reference; synonyms; Family and Order). Dentiraja australis (Macleay 1884), synonymous with Dipturus australis and Raja australis Kingdom: Animalia Phylum: Chordata Class: Chondrichthyans Subclass: Elasmobranchii Order: Rajiformes Family: Rajidae Genus: Dentiraja Species: Australis This species was originally classed as Raja australis (Macleay 1884). A more fine-scale assessment of Australian skates placed it in the Dipturus genus (Last and Yearsley 2002; Last and Stevens 2009; Weigmann 2016) however a recent molecular assessment has reclassified it within the Dentiraja genus (Last et al., 2016, unpubl.). There is no evidence of hybridisation with other species. CONVENTIONALLY ACCEPTED Is the species’ taxonomy conventionally accepted? Yes No If the species is not conventionally accepted please provide the following information required by the EPBC Regulations 2000: • a taxonomic description of the species in a form suitable for publication in conventional scientific literature; OR • evidence that a scientific institution has a specimen of the species, and a written statement signed by a person who is a taxonomist and has relevant expertise (has worked with, or is a published author on, the class of species nominated), that the species is considered to be a new species. n.a. DESCRIPTION Provide a description of the species including where relevant, distinguishing features, size and social structure How distinct is this species in its appearance from other species? How likely is it to be misidentified? Dentiraja australis is a skate of medium size, with males and females both reaching approximately 55cm total length (TL; Last et al. 2016). Its disk is dorsoventrally flattened, quadrangular and smooth, usually brown with pale yellow blotches on the dorsal side (Last et al. 2016; Figure 1). Its snout is moderately elongated. Similar to other skates, it has five pairs of ventral gill slits and its flat pectoral fins are fused to the head. Its eyes are located dorsally, along with relatively large spiracles. It has two dorsal fins located near the tail tip, and rows of thorns along the tail (three in males, five in females; Last et al. 2016). Page 2 of 19 It has several features that are distinctive from similar skates, including the breadth of the tail, number of thorn rows, a single thorn in the central disc area and males have malar thorn patches near each eye (AFMA 2015; Last et al. 2016). Misidentification of this species is therefore unlikely. The social system of D. australis is unknown. DISTRIBUTION Provide a succinct overview of the species’ known or estimated current and past distribution, including international/national distribution. Provide a map if available. Is the species protected within the reserve system (e.g. national parks, Indigenous Protected Areas, or other conservation estates, private land covenants, etc.)? If so, which populations? Which reserves are actively managed for this species? Give details. Skates of the Dentiraja genus are endemic to Australian waters and D.australis is found only on the east coast. It has a relatively restricted latitudinal and bathymetric range, occurring on the inner continental shelf to the upper slope (Last et al. 2016), from Moreton Bay (Queensland) in the north to Tathra (New South Wales) in the south (Stevens and Valenti 2009; Figure 2). There is evidence to suggest that other skates are geographically philopatric (Flowers et al. 2016), however the home range and movement patterns of D. australis are not known. Understanding the seasonal movements of this species should be a priority as this has major implications for fisheries impacts (the main threat to its viability, see Threats) and its response to management actions. There are no captive populations used for propagation. Heupel et al. (2018) found a range overlap of only 9.6% with Commonwealth marine protected parks (9.6% of distribution), all of which has no fishery exclusions. Therefore its range is afforded very little protection. The extent of state-based protected areas has not been assessed. The species is not known to occur within an ecological community listed under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act). BIOLOGY/ECOLOGY Provide a summary of biological and ecological information. Include information required by the EPBC Regulations 2000 on: • life cycle including age at sexual maturity, life expectancy, natural mortality rates • specific biological characteristics • habitat requirements for the species • for fauna: feeding behaviour and food preference and daily seasonal movement patterns • for flora: pollination and seed dispersal patterns The biology and ecology of this species is poorly understood, but inference from closely related and sympatric skates can provide some insights. It is known that males and females both reach around 55cm TL (Last et al. 2016). Generation length is unknown but males are thought to be sexually mature at 43-48cm TL (Last and Stevens 1994). The average life expectancy is also unknown but closely related Australian skates are thought to live between 9 – 12 years (Treloar 2008). This late maturity suggests that, as with many skates and rays (Simpfendorfer and Kyne 2009), this species may have protracted recovery rates and are therefore vulnerable to exploitation. Natural mortality rates are unknown. D. australis is oviparous, and eggs are deposited in large, quadrangular cases with corner extensions. Our knowledge of its breeding system is limited, although some detail is known about related species. For example, the similarly sized and late maturing D. lemprieri (Thornback skate; maximum size 55cm; females mature at 42cm) have a gestation period of 4 to 5 months and a birth size of 9.5 to 10.8cm (Treloar 2015). It is generally agreed that this group of species have low productivity and are highly vulnerable to extinction with ongoing levels of exploitation (Simpfendorfer and Kyne 2009; Treloar 2008). D. australis is found on the inner continental shelf to upper slope, at depths of 22 to 325m, and is a demersal species that spends time resting on the sandy substrate (Last et al. 2016). Its trophic level is 3.34, Page 3 of 19 suggesting it is a meso-predator (Reis and Figueira 2020). It is likely to be an ambush predator, with a benthic diet of crustaceans, cephalopods and bony fish (Reis and Figueira 2020). Threats IDENTIFICATION OF KNOWN THREATS AND IMPACT OF THE THREATS Identify in the tables below any known threats to the species, under the provided headings indicate if the threat is past, current or future and whether the threats are actual or potential. Past threats Impact of threat Mortalities from commercial Given its demersal habitat, D. australis is most impacted by small and trawl fisheries. large-scale trawl operations (Stevens and Valenti 2009), predominantly from the otter trawl method (Figure 3), and to a lesser extent from the mid-water Danish Seine method (Walker and Gason 2007). It has been caught as marketable byproduct in the Commonwealth Trawl Sector (CTS) of the Southern and Eastern Scalefish and Shark Fishery (SESSF; Figure 4) which has been operating (in various forms) since 1915 (Stevens and Valenti 2009; Novaglio et al. 2018). In particular, the upper slope of NSW has been subject to relatively intensive trawling since 1968 (Graham et al. 2001). Historical estimates of catch and landing numbers are hampered by the lack of species-specific records (Stevens and Valenti 2009) but these records can still provide insight into population trends for this species. For example, a fishery-independent survey showed a decline of 83% in skate catch-per-unit-effort (CPUE) in southern NSW over 20 years (falling from 32-33 kg/h in 1976-77 to 4-8 kg/h in 1996-97; Graham et al. 2001; Graham et al. 1997). However, it is known that D. australis was one of the most common skates on the central-eastern continental shelf and this was reflected in the high proportion of D.australis in catches from its depth range (Graham et al. 2001). It is therefore likely that this decline is reflective of the species trend. Furthermore, data from the Integrated Scientific Monitoring Program (ISMP) of the SESSF and fisher logbooks from the South Eastern Trawl Fishery (now the CTS), showed a substantial decline of D. australis was observed, following a rise-peak-decline trend (from 1998 -2006, peaking in 2003; Walker and Gason 2007). During this period, the total annual catch of this species was 157 239 kg, all of which was discarded (Walker and Gason 2007). The targeted teleost species in the SESSF are now under quota and skates have increasingly been considered as an attractive alternative meat for consumption (Stevens and Valenti 2009). Skates in this region were generally discarded, but it is likely now that larger skates are more often retained as marketable byproduct (Stevens and Valenti 2009). In 2005 observer-monitored catches found a 29% retainment rate of D. australis (ISMP data in Stevens and Valenti 2009). Recent bycatch restrictions for D. australis may offset this (see Threat Abatement), but this is yet to be measured, and the post-release survival of discarded skates is unknown. Monitoring harvest numbers through sales is difficult due to ambiguous labelling in the major markets locally and nationally (Stevens and Valenti 2009) and requires on inference from pooled species numbers. For example, 43 tonnes of “flaps” (pectoral fins?) were sold in 2002 (around 134 tonnes live weight; Stevens and Valenti 2009). Trawling may also disturb benthic habitat and key behavioural processes, which in turn can have sublethal impacts that affect the species viability. It may also impact on recruitment, for example by damaging egg cases or juvenile refuges ( ).