© Baker, J.L. (2009) Marine Species of Conservation Concern in South Australia Full citation Baker, J.L. (2009) Marine Species of Conservation Concern in South Australia: Volume 1 - Bony and Cartilaginous Fishes. Report for the South Australian Working Group for Marine Species of Conservation Concern. J. Baker (consultant); Science and Conservation Division, and Coast and Marine Conservation branches of S.A. Department for Environment and Heritage (DEH); Marine and Coastal Community Network of S.A. (MCCN), and Threatened Species Network (TSN). Web version published by Reef Watch, South Australia.

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Greenback Flounder

Family Name:	Pleuronectidae
Scientific Name:	Rhombosolea tapirina Günther, 1862
Recommended Status in S.A:	Near Threatened (also in SE Australia)
Rationale:  The species is included here because (i) R. tapirina is a strongly site associated benthic fish within estuaries and shallow muddy and sandy bays, and is vulnerable to nearshore, site-specific impacts, such as decline in estuarine habitat quality; (ii) there are few estuaries in S.A. to support the life history phases of this species, and the major estuaries in which the species is found in S.A. are subject to significant, ongoing impacts, some of which may worsen over time, particularly reduced freshwater inputs; (iii) the species is considered vulnerable to impacts due to contaminated sediments (e.g. in estuaries);  (iv) Greenback Flounder is heavily fished by commercial and recreational fishers in areas where it is most abundant (e.g. Tasmania, Victoria and South Australia), with few regulations, and little indication of sustainability of catches over space or time due to inadequate stock assessment; however, long term catch and effort data indicate that populations may be declining in southern Australian States; (v) current legal minimum sizes in southern Australian States might be inadequate to ensure that a fish spawn at least once before capture (and there is no legal minimum size at all in S.A.); and (vi) there is little information on the population dynamics of this species over space and time, particularly in areas where it is targeted as a food fish.

Page Contents

Current Conservation Status

(No listings known)
 

Distribution

Southern Australia and New Zealand

The species has been recorded in southern Australia (N.S.W. through to W.A.) (Hutchins and Swainston, 1986) and New Zealand (Paulin et al., 1989; Beentjes et al., 2002).
The species is common in Victoria, Tasmania and South Australia (Hutchins and Swainston, 1986). As at the mid 2000s, the stock structure of greenback flounder populations from W.A. and S.A. had not been studied (Jones et al., 2005). During an early study of Tasmanian and Victorian populations, Kurth (1957, cited by Jones et al., 2005) reported that populations of Greenback Flounder in western Tasmania were genetically distinct from south-eastern and northern Tasmanian populations and Victorian populations. A more recent study (van den Enden et al., 2000) reported that samples from the west coast of Tasmania and from Victoria were genetically isolated from each other, and also from samples taken from other parts of Tasmania (the latter of which were considered similar).  
In New Zealand, Greenback Flounder occur around the South Island, the Auckland Islands and Campbell Island. Significant genetic differences exist between Australian and New Zealand populations (van den Enden et al., 2000, cited by Jones et al., 2005).
 

South Australia

Within S.A., the species is known mostly from the gulfs, and also the Murray Mouth / Goolwa region (e.g. Geddes, 2005), and the Coorong area, where it is commercially fished. Examples of locations in S.A. where Greenback Flounder occurs include southern Eyre Peninsula (e.g. Coffin Bay); northern Spencer Gulf (e.g. Whyalla, Port Augusta, and creeks in the Port Pirie area); western and south-western Gulf St Vincent (e.g. Sheoak Flat, Port Julia, Stansbury), northern GSV (e.g. Port Gawler; Price; Wakefield River; Light River delta); metropolitan area (e.g. Barker Inlet and Angas Inlet; Port Adelaide; West Lakes; Patawalonga; Onkaparinga Estuary); Kangaroo Island (Middle, Cygnet, American and Chapman rivers); parts of Encounter Bay, including the Victor Harbor area, and numerous locations in the Murray Mouth, Murray Lakes (Alexandrina and Albert), Goolwa and the Coorong area (British Museum of Natural History records, 1925; National Museum of Natural History record, 1970, cited in Anonymous, 2001a; Branden et al., 1974; Hall, 1984; Connolly, 1994; Ye et al., 2002; Geddes, 2005; Bloomfield and Gillanders, 2005; Adelaide University data and Flinders University data, cited in Hammer, 2006a; Gillanders et al., 2008; Australian Museum records, Museum of Victoria records, South Australian Museum records, cited in OZCAM database, 2008).
In the Murray Mouth / Coorong region of S.A., Greenback Flounder are rarely captured in marine waters outside of the Coorong (Hall, 1984); hence it is considered that the species may be an estuarine resident in the area (MDBC, 2003), that completes its life cycle in the sheltered waters of the Coorong lagoons (Jones et al., 2005).
 

Habitat

Greenback Flounder is common on silty sand substrates in estuaries and shallow, sheltered bays (Hutchins and Swainston, 1986, Kailola et al., 1993), but has been recorded in deeper waters down to about 100m.
It is classified as an estuarine resident (Whitfield, 1999, cited by Higham et al., 2002). The species has been recorded in a number of estuarine areas in Tasmania (e.g. Lara and Neira, 2003); South Australia (e.g. Branden et al., 1974; Hall, 1984; Connolly, 1994; Bloomfield and Gillanders, 2005; Hammer, 2006b), Victoria (e.g. Hindell and Jenkins, 2004; Smith and Hindell, 2005) and Western Australia. Juveniles occasionally enter rivers (Kailola et al., 1993).
In the Barker Inlet Estuary in north-eastern Gulf St Vincent in S.A., the species has been recorded on bare (unvegetated) sandy and muddy bottoms (e.g. Connolly, 1994; Bloomfield and Gillanders, 2005), on which they are well camouflaged, and less commonly in seagrasses (Bloomfield and Gillanders, 2005).
In Victoria, the species has been recorded in a variety of habitats. Adult R. tapirina have been found commonly on bare substrate (Jenkins et al., 1997), but also in close association with sediments in seagrass beds (Klumpp and Nichols 1983; Brown and Davies 1991; NRE Victoria, 1996; cited by EPA Victoria 2001; Jenkins et al., 1997). Enrichment of sediments with seagrass debris may benefit flounder populations by assisting the increase in invertebrate food  production (Jenkins et al., 1997, cited by Edmunds et al., 2004). In Port Phillip Bay, the species has been recorded in mangroves; as well as over mudflats, and on unvegetated sand, and in seagrass beds (Hindell and Jenkins, 2005). Larvae have been commonly recorded in Port Phillip Bay (Jenkins, 1986). Greenback Flounder have been recorded commonly on unvegetated sediments adjacent to seagrasses (e.g. in Swan Bay - Plummer et al., 2003; and Corner Inlet – O’Hara et al., 2002). Swan Bay supports higher populations than Port Phillip Bay, and is considered to be a nursery area which provides conditions of enhanced rates of growth and survival. In addition to Port Phillip Bay, the species has been recorded in mangroves in Western Port Bay, Corner Inlet and Barwon River Estuary (e.g. Hindell and Jenkins, 2004; Smith and Hindell, 2005), and both adults and juveniles have also been recorded on unvegetated mudflat habitat adjacent to mangroves (Hindell and Jenkins, 2004). Also in Victoria, Crinall and Hindell (2004) recorded R. tapirina as a common inhabitant of saltmarsh flats.
In Tasmania, Greenback Flounder have been recorded on unvegetated mud, and to a lesser extent in Zostera / Heterozostera beds and over bare sand, off beaches and in various shallow bays (e.g. Jordan et al., 1998). In Tasmania, Greenback Flounder are more abundant on the fine sand found on large sheltered sand flats, than in seagrass beds (Crawford, 1984). The species has been recorded in numerous estuaries around Tasmania, and also in estuaries on islands in Bass Strait (Edgar et al., 1999).
Greenback Flounder have a large temperature and salinity tolerance (Kailola, et al., 1993, cited by Jones et al., 2005).
According to Crawford (1984, cited by Morton et al., 2005), in Tasmania Greenback Flounder are sexually partitioned in the habitat, with females most abundant in shallow water (5-10 m depth), and males found in deeper water (10-25 m depth). There may also be seasonal migration, with R. tapirina being more abundant in deep water throughout the winter/spring period and in shallow water in summer/autumn (Parry et al. 1995).
 

Notes on the Biology

Growth

Greenback Flounder grows to about 38cm – 40cm (Hall, 1984; Hutchins and Swainston, 1986; Kailola et al., 1993), or up to 45cm (Last et al., 1983, cited by Morton et al., 2005), but they are mostly found at sizes less than 30 cm (Jordan et al., 1998, cited by Morton et al., 2005).
Fish of about 40cm and 0.6kg in weight may be about 3 to 4 years of age (Hall, 1984; Kailola, et al., 1993, cited by Jones et al., 2005). In Tasmania, 6-13 cm fish are most likely the 1+ age class (Jordan et al., 1998).
One of the maximum sizes recorded was 0.820kg (Hutchins and Swainston, 1986), a specimen taken by spearfishing (Australian Underwater Federation Inc., 2003). In Victoria, one of the maximum sizes recorded by fishing is 0.55kg (Australian Anglers Association – Victorian Division, 2003).  
 

Diet

A study in Victorian bays showed that juvenile Greenback Flounder in Swan Bay (a sheltered bay with muddy sediments and a well-developed seagrass-detrital system), ate almost entirely epibenthic harpacticoid copepods. Juvenile Greenback Flounder in Port Phillip Bay (a more exposed area with coarser sandy sediments) ate epibenthic harpacticoids, harpacticoid nauplii and gammaridean amphipods (Shaw and Jenkins, 1992). In Victoria, juvenile greenback flounder grow at faster rates in areas of higher food supply (Jenkins et al., 1993, cited by Morton et al., 2005). In Tasmania, Crawford (1984, cited by Morton et al., 2005) recorded amphipods and polychaetes in the diet of juvenile Greenback Flounder, and polychaetes and molluscs in the diet of adults (Crawford, 1984).
Larvae feed during daylight hours (Chen, et al., 1999; Cox and Pankhurst, 2000, cited by Jones et al., 2005), in contrast to juveniles and adults, which feed on rising tides at night on shallow mud banks (Kailola, et al., 1993, cited by Jones et al., 2005 and Morton et al., 2005). Various types of microplankton, including bivalve veligers, are important in the diet of larval flounders (Jenkins, 1988).
 

Reproduction

Size at maturity is between 19 and 30cm (Kailola, et al., 1993, cited by Jones et al., 2005 and Morton et al., 2005), and during one study, 60% of Greenback Flounder females were mature by 24 cm length (Kurth, 1957, cited by Crawford, 1984 and Morton et al., 2005).
Flounders live on the sea floor, but are pelagic spawners (Nelson, 2006). Total fecundity appears to be high, with estimates of over 820,000 eggs in a 25 cm greenback flounder (Jordan, 1994b). This species is thought to move into deeper water to spawn (Crawford, 1984).
Tasmanian studies have indicated that the species is a serial spawner, with a protracted spawning season from at least March (May in SE Tasmania) to October (December in SE Tasmania), with a peak from late winter to early summer (Kurth, 1957; Crawford, 1984, cited by Jordan et al., 1998), and that spawning occurs in the deeper regions of estuaries, tidal rivers and offshore waters (Kurth, 1957, cited by Jones et al., 2005). Larvae have been recorded in estuaries such as the Tamar (Lara and Neira, 2003).
In Victoria, spawning occurs offshore during periods of protracted cold water between June and October (Jenkins 1986; May and Jenkins 1992, cited by EPA Victoria 2001). A study in Swan Bay in Victoria showed that although settlement of larvae to a benthic existence was continuous from July to October, there were distinct winter and spring cohorts, with the latter growing faster (i.e. 0.23mm per day) (May and Jenkins, 1992).
Female greenback flounder are capable of ovulating several times within a reproductive season (Barnett and Pankhurst, 1999, cited by Jones et al., 2005). Tank experiments indicate that wild stocks are likely to spawn before dawn during winter and spring, possibly synchronised with a lunar phase (Pankhurst and Fitzgibbon, 2006).
In the Coorong lagoons in S.A., temperature-dependent freshwater inflows are thought to provide a critical spawning stimulus for Greenback Flounder and other estuarine dependent species (Jones et al., 2005). In addition to spawning success, the magnitude, timing and duration of freshwater flows affect larval survival and development (Hall, 1984; Pierce and Doonan, 1999, cited by Jones et al., 2005). Juveniles tend to remain in the estuary, but have also been recorded upstream (MDBC, undated). 
Within limits, age at metamorphosis decreases as temperature increases (Chambers and Leggett, 1992). Larvae are fully settled about 65 days after hatching, at less than a centimetre in length (Crawford, 1984; Crawford, 1986, cited by Jones et al. 2005). Metamorphosing larvae migrate to shallow, unvegetated habitats, which are utilised in the early juvenile stage (Edgar and Shaw 1995a; Jenkins et al. 1993, cited by EPA Victoria, 2001).
Greenback flounder larvae spend up to 30 days in the plankton, settling at a length of around 6mm (Jenkins et al., 1993). Larvae are weak swimmers, and rely on water currents or wind-induced surface water movements to drift inshore to settle (Crawford, 1984, cited by Morton et al., 2005). During late winter to early summer newly-metamorphosed greenback and long-snouted flounder settle on estuarine sand flats. Substrate type and salinity preferences appear to be the major determinants of their distribution (Burchmore, 1982, cited by Morton et al., 2005).
 

Fisheries Information

Commercial – Commonwealth

R. tapirina is a commercial species in southern Australia. The marketing name is “Greenback Flounder (Seafood Services Australia, 2003).
The species is part of the bycatch in the Commonwealth-managed SESSF (Southern and Eastern Scalefish and Shark Fisheries) (AFMA, 2002a).
The species is part of the bycatch in the South East Trawl Fishery (Wayte et al., 2004; Bromhead and Bolton, 2005). For example, in the Danish seine sub-fishery of the SETF, an Integrated Scientific Monitoring Program (ISMP) reported that in 2 shots, 1kg of R. tapirina specimens were retained, and 2kg were discarded (Wayte et al., 2004).  In the otter trawl sub-fishery of the SETF, 0.5kg were retained in 2 shots, and 0.1kg discarded (Wayte et al., 2004).  
The species is caught in minor, incidental numbers in 6-inch shark nets used in the Southern Shark Fishery (= Gillnet, Hook and Trap Fishery) in Bass Strait and off South Australia (Walker et al., 2005). 
 

Commercial – Southern States

In the commercial fishery in Tasmania State waters, there are limited number of scalefish licences, and also area closures. Tasmanian catches of flounder comprise mainly Rhombosolea tapirina, with a lesser component of A. rostratus, and minor quantities of others (Smith and Heran, 2001; Ziegler et al., 2006). The species are not distinguished in catch returns (Morton et al., 2005). The fishery is concentrated in south-eastern and eastern Tasmania, with lesser catches in some years from mid-western and north-eastern Tasmania, and Kent Group islands (Ziegler et al., 2006). Flounders are taken mainly by spears and inshore gill / “graball” nets, but also inshore trawl, seine nets, dip nets, and occasionally by line (Smith and Heran, 2001; Morton et al., 2005). During the 1990s and 2000s, the overall regional distribution of effort based on days fished changed little over time (Ziegler et al., 2006). The combined catches of both species (R. tapirina and A. rostratus) rose in the late 1980s from less than 20 tonnes per annum to over 40 tonnes during the early 1990s, but have since declined steadily to about 12t in 2000/01, 10t in 2002/03 (Morton et al., 2005), and 14t in 2004/05 (Ziegler et al., 2006). Spear catch rates have remained relatively stable since the mid 1990s, but gillnet catch rates have generally declined over this period (Lyle et al., 2004, cited by Morton et al., 2005). The gill net catch during the early 2000s was 5.2 tonnes, making flounder the third most important species taken by gill nets (Smith and Heran, 2001).
In Tasmania, Greenback Flounder has also been a minor bycatch of scallop dredging in the Bass Strait Central Zone Scallop Fishery (Semmens et al., 2000; Bromhead and Bolton, 2005). For example, during a survey in 2000, only 1 specimen was recorded in 7 dredge tows (Semmens et al., 2000). This fishery has a zero TAC for 3 years from the start of 2006 (so is currently closed) (J. Pogonoski, pers. comm., 2007).
In Victoria’s bays and inlets, the average annual commercial catch (tonnes) of R. tapirina in the five years from 1998/99 to 2002/03 was estimated to be 23.2 t (VBIFA, 2005). Catches are mostly taken from Port Phillip Bay and Corner Inlet, and annual yields in recent years are as follows: 2000/01 = 15t; 2001/02 = 19t; 2002/03 = 19t; 2003/04 = 18t and 2004/05 = 26t (Department of Primary Industries, Victoria, 2006b).
In S.A., Greenback Flounder is one of the species taken commercially in the Lakes and Coorong Fishery (Sloan, 2005; Jones et al., 2005), and the species has been taken there since the late 1800s. Since barrage construction in the Lakes and Coorong region, near the Murray Mouth, the total commercial catch has varied substantially between years (Jones et al., 2005). In S.A. Lakes and Coorong fishery, the commercial catch has varied between 4 to 65 tonnes since 1984/85 (Jones et al., 2005), and catches have displayed peaks and troughs over time (e.g. over the 18 year cycle from 1984 to 2002; see Jones et al., 2005, Figure 20). The maximum catch in recent decades was 65t, in 1990/91. Catches were 40t in 1999/2000; under 30t per annum in 2000/01 and 2001/02 (Jones et al., 2005), and less than 10t per annum in 2002/03 and 2003/04 (Knight et al., 2005).
The most common gear used in the commercial fishery is bottom set gillnets (mesh nets), but hauling nets (seine nets) and fish spears are also used to a lesser extent. Commercial fishers only target flounder during seasons when stocks reach a level of abundance that makes catching and marketing economically viable; in all other years the catch reflects non-targeted by-product (Hera-Singh, G. 2004, pers. comm., cited by Jones et al., 2005). Greenback Flounder are the most common species caught in the Lakes and Coorong Fishery, but catches are also known include other flounder species such as the Small-toothed Flounder (Jones et al., 2005). There is a legal minimum size of 25cm for Greenback Flounder taken in the commercial fishery.
When caught in the bycatch of the South Australian Rock Lobster fishery, flounders are permitted to be retained for sale (Sloan, 20003a).
 

Recreational

Recreational survey catch statistics (e.g. Henry and Lyle, 2003) usually group recreational catches of flounders with soles and other flatfish, and summary statistics, as well as other State-level data, are provided in the section on Recreational Fishing, at the beginning of this chapter. However, Greenback Flounder is one of the species for which species-specific data are available, and the National Recreational and Indigenous Fishing Survey estimated that the total recreational catch of Greenback Flounder in South Australia was 2,994 fish in 2000/01 (Henry and Lyle, 2003). In some recent years, recreational fishers may have landed up to 28% of the total catch of Greenback Flounder in the Coorong. In S.A., recreational fishers catch flounder with fish spears, rods and lines, and also a limited number of registered small mesh nets have been used recreationally in the Lakes and Coorong area, and Lake George in the South East. Although these nets are mainly used for targeting Yellow-eye Mullet, Greenback Flounder is bycatch (Jones et al., 2005).
In N.S.W., larger flounder species are caught by recreational fishers and the total recreational catch of flounder (species combined) in N.S.W. is estimated to be about 5t per annum (N.S.W. Department of Primary Industries, 2004).
In Tasmania, there is a minimum legal size of 25cm for all flounder species taken by recreational fishers (Morton et al., 2005) and there is a personal possession limit of 30 (DPIW Tasmania, 2008). The estimated recreational catch of flounder in 2000/01 of 21 tonnes was double the size of commercial catch during that period, indicating the importance of the recreational component of this fishery (Henry and Lyle 2003, cited by Lyle et al., 2004; Lyle, 2005). Catches were concentrated in Derwent-Channel area (35%) and Fredrick Henry-Norfolk Bay (24%), followed by the eastern north coast (17%), west coast (11%) and south-east (9%) (Morton et al., 2005). Of the 75,000 specimens caught, 71,000 were retained (Morton et al., 2005). Although spearing at night (using lights) from the shore is the main method (accounting for 80% of the catch; Morton et al., 2005), R. tapirina is reported to be taken by recreational gillnetting over reefs and soft bottom habitat in south-eastern Tasmania, and over soft bottom habitat in northern Tasmania (Lyle et al., 2000). The gillnet catch accounts for about 15% of the total, with minor catches by beach seines. Greenback Flounder that were examined from the 2000/01 survey ranged between 22-33 cm TL, with a mean size of 30 cm TL (Lyle et al., 2002, cited by Morton et al., 2005). Creel surveys conduced during 1997/98 revealed that Greenback Flounder catches ranged between 20-37 cm TL, with a strong mode at 27 cm and average size of about 27 cm (Lyle and Campbell, 1999, cited by Morton et al., 2005).
In Victoria, the minimum legal size is 23cm, for all flounder species taken by recreational fishers, with a bag limit / possession limit of 20 flounder (DPI Victoria, 2007b). Some clubs and associations keep records of the maximum sizes caught (e.g. Australian Anglers Association, Victorian division, 2003). The species is also taken by spearfishers (Nevill, 2006)
For recreational fishers in South Australia, there is a daily bag limit of 20 flounder (all species) and a boat limit of 60. There is no legal minimum size in S.A. for the recreational fishery (PIRSA, 2008a, 2008b). 
In W.A., there is a legal minimum size of 25cm for all flounder species, and a combined daily bag limit of 8 flathead and flounder (all species) in the West Coast, Gascoyne and South Coast regions (Department of Fisheries, 2007c, 2008a, 2008b).
 

Vulnerable Characteristics of the Species and Threatening Processes

Benthic fishes in general have limited mobility, more localised reproduction than most pelagic species, and more limited opportunity for population dispersal, all of which can increase the vulnerability of populations to decline.
Regulation of rivers (and consequent impacts on water quantity and quality) may significantly impact populations of this species. For example, Jones et al. (2005) reported there has been a significant reduction in the total catch of Greenback Flounder from the Coorong lagoons in S.A. since the early 1940s, when the barrage network was completed. The decrease in production is thought to be largely due to reduced spawning success and lower survival rates of larvae, caused by limitations on the availability of estuarine habitat, disrupted natural flow regimes, and changes to estuarine conditions (Jones et al., 2005). The loss of habitat in the vicinity of Lake Alexandrina and Lake Albert has probably reduced numbers of Greenback Flounder in the past. Also, in the Coorong lagoons in South Australia, temperature-dependent freshwater inflows are thought to provide a critical spawning stimulus for Greenback Flounder and other estuarine dependent species (MDBC, 2003, cited by Jones et al., 2005). According to a report by Fluvial Systems Pty Ltd (2002), the “confusion of ecological signals” resulting from hydrological and geomorphic changes interferes with breeding/recruitment of fish such as greenback flounder, which develop to advanced stages of reproduction, but are deprived of well-defined flood flow cues, and therefore do not progress to spawning. Over the long term, reductions in flow from river regulation may be worsened by ongoing drought condition, exacerbated by global warming and climate change.
Periodic closure of the Murray Mouth (during periods of low flow), may adversely affect populations of this estuarine-resident species, due to degraded water quality, and salinity impacts (Higham et al., 2002, also cited by Sloan, 2005).
As indicated above, the species may be susceptible to population impacts due to decline in estuarine habitat and water quality, but there are no species-specific data for most parts of the range. Estuaries are often subject to many pollutants, and other impacts that degrade water quality and habitat. Polluted estuarine areas can take a long time to recover, as toxicants accumulate in their sediments (Pogonoski et al., 2002). There are few pristine or near pristine estuaries remaining in South Australia, and most of those in which Greenback Flounder have been recorded are subject to numerous impacts (see Bucher and Saenger, 1989; Lewis et al., 1998; Barnett, 2001; GeoScience Australia, 2001; Baker, 2004; Gillanders et al., 2008).
In Tasmania, experimental work by Mondon et al. (2000) showed that laboratory-reared R. tapiria displayed a depressed immune response when raised on contaminated sediments (from Deceitful Cove, Tamar River) compared with control sediments (from Port Sorrell), and the impact on flounder physiology was worse when flounder were kept on disturbed compared with undisturbed contaminated sediments. Further impacts on Greenback Flounder from exposure to the contaminated sediment included growth reduction, epidermal erosion, and necrosis of the liver (Mondon et al., 2001). Therefore, there is a potential risk of an increased exposure of species such as flounder to contaminated sediments during any dredging activities or other activities resulting in re-suspension of contaminated sediments, and such exposure could result in adverse effects on aquatic life (Nowak, 2006). In south-eastern Australia, the effects of heavy metal contamination have on Greenback Flounder have also been investigated (Australian Marine Ecology web site, 2005). In Greenback Flounder, recorded contaminants include dioxins (e.g. in specimens from the Yarra River in Melbourne: uncited reference, in Drew and Frangos, 2006). but it is noted that the species can exist in relative abundance on metal-contaminated sediments (e.g. Macquarie Harbour in Tasmania – O’Connor et al., 1996). There are few other specific studies on the impacts of pollutants on flounders in Australia, but it is noted that in the northern hemisphere, sub-lethal effects of sediment contamination (from municipal sources such as  sewage; also industrial pollutants, and other contaminants such as tri-butyl tin from ship and boat anti-foulants) have been recorded. Impacts upon flounders from contaminants include changes in body chemistry, hepatic and other lesions, and reproductive impairment (e.g. Johnson et al., 1993; Myers et al., 1998; CSTEE, 1999; WWF, 1999; Rice et al., 2000).
The impacts of critical habitat degradation may be exacerbated by the combined effects of commercial and recreational fishing, in areas where this species is regularly caught (e.g. Tasmania, Victoria and S.A.). For example, in South Australia, where Greenback Flounder has been caught for well over 100 years, an education resource by the Murray Darling Basin Commission (undated) included commercial and recreational fishing amongst reasons for decline in Greenback Flounder in the Coorong region. In Tasmania, there has been a decline during the past decade in the commercial catch (Smith and Heran, 2001; Morton et al., 2005). During the early and mid 2000s, the State-wide catches were below the reference range for management action, triggering the catch performance indicator for the seventh year running (Ziegler et al., 2006). Catch rates from spearing and graball netting were also declining during that period (Ziegler et al., 2006). The current status of the flounder stocks in Tasmania is unknown, but it appears that they have declined in recent years (Ziegler et al., 2006), and the fishing industry agrees that that is the case, in addition to market factors that have influenced effort (Ziegler et al., 2006). Similarly in Victoria, both fisheries data and anecdotal evidence suggest that there has been a decrease in abundance of Greenback Flounder in Victorian waters (Reef Watch Victoria, undated).  
There may be impacts on the genetic variability in this species, if aquaculture-raised individuals are released into the wild (e.g. van den Enden et al., 2000; Cole, 2002).
 

Research Requirements

In the Murray Mouth and Coorong region, some of the research requirements include: a measure of relative abundance of adults, juveniles and larvae; more information on spawning; distribution of larvae and juveniles, and habitat requirements; knowledge of preferences in hydrology/flow and salinity (for all life stages); and stock structure and migration (Murray Darling Basin Commission, 2006).
Regular monitoring of recruitment over space and time is required.
In Tasmania, little is known about the life history and population dynamics of flounders (in the wild), and there is no biomass estimate (Morton et al., 2005). To the present, there has been inadequate information available with which to assess stock status (Morton et al., 2005). Key biological parameters for flounder populations should be described. Size at maturity information is particularly important because the scarce information available indicates that not all flounder are mature at 25 cm TL, the current recreational minimum size limit (Morton et al., 2005).
 

Research Notes

Jones et al. (2005) reported that the total commercial catch and CPUE in the Lakes and Coorong Fishery could be used as an index of inter-annual changes in stock abundance in that area.
 

Management Requirements

In South Australia, there is potential for Greenback Flounder population numbers to be significantly increased in the Coorong lagoons under an improved barrage flow strategy (Hall, 1984; Pierce and Doonan, 1999; MDBC, 2003, cited by Jones et al., 2005). In estuarine areas such as the Coorong, future management must focus on increasing the number of successful annual spawning events and maximising the opportunities for larvae survival and development, through improved barrage flow manipulation (Jones et al., 2005).
In southern States (particularly Tasmania, Victoria and S.A.), recreational catches of Greenback Flounder may be a significant component of the harvest, and trends in the recreational fishery should be examined over space and timer to provide a more informative assessment of flounder stock status.
As indicated in Research Requirements, in Tasmania there is a need to evaluate appropriateness of current management arrangements in relation to biological parameters (such as size at maturity) and resource sustainability (Morton et al., 2005)
Assessment is required of the sustainability of catches over space and time, in commercial fisheries in Tasmania, Victoria and South Australia.
Further recreational fishing controls (e.g. legal minimum sizes, and possession limits) are required in areas where these do not yet exist, and enforcement is also required.
 

Management Notes

In southern Australia, management controls on the commercial fisheries for Greenback Flounder include limits on the numbers of fishing licences issued; restrictions on the type of fishing gear  used; closed seasons and closed areas in  some estuaries; and minimum legal size limits. There are catch limits and legal minimum sizes for recreational fishing, as listed above.
In S.A., the Greenback Flounder population in the Coorong is managed as a distinct unit stock, considered to be reliant on local spawning events within the Coorong lagoons for successful recruitment (Jones et al. 2005).
 

Other Information

R. tapirina is considered to be one of the key fish species (other than Sardinops pilchards) that is susceptible to viral haemorrhagic septicaemia virus (VHSV) (Commonwealth of Australia, 2003), but the risk of this disease entering Australian native fish populations is considered to be “very low” (Commonwealth of Australia, 2003).
A number of studies have assessed the potential of this species for aquaculture in Australia (e.g. van den Enden et al., 2000; N.S.W. DPI, undated), and New Zealand (e.g. van den Enden et al., 2000; Jeffs, 2003) In Australia, numerous experiments in rearing have been undertaken during the past two decades (e.g. Crawford, 1984; Hart, 1994; Hart and Purser, 1996; Hart et al., 1996; Butler et al., 1996; Carter et al., 1996; Girling, 1997; Barnett and Pankhurst, 1998; Bransden and Carter, 1999; Chen et al., 1999; Carter and Bransden, 2001; Girling et al., 2003; Shaw et al., 2003). In recent years, R. tapiria have been successfully bred in tanks (Pankhurst and Fitzgibbon, 2006; Shaw et al., 2006).  During the past decade, approval has been given by PIRSA (e.g. S.A. Government Gazette, Friday, 31^st March, 2000) for Greenback Flounder to be imported into South Australia and kept in tanks. During the past decade, State fisheries agencies in most parts of southern Australia have considered the species to be prospective for aquaculture.   
The species has been recorded in a number of marine protected areas in Victoria, such as Port Phillip Heads Marine National Park (MNP) (Swan Bay and Mud Islands), Yaringa MNP, French Island MNP, Corner Inlet MNP, and Ricketts Point Marine Sanctuary (Plummer et al., 2003).