© 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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Small-tooth Flounder / Smalltooth Flounder

Family Name:	Paralichthyidae
Scientific Name:	Pseudorhombus jenynsii (Bleeker, 1855)
Recommended Status in S.A:	Data Deficient
Rationale:  The species is included here because P. jenynsii (i) occurs in coastal areas such as shallow sandy bays and estuaries, and may thus be vulnerable to coastal impacts; in particular, estuarine habitat for this species is geographically limited in South Australia, and a number of major estuarine habitats in S.A. are significantly polluted, but there are no specific data on potential impacts on flounder populations; (ii) is taken by commercial and recreational fishers across the range (including S.A.), with no indication of sustainability of catches over space or time; (iii) is considered to be highly vulnerable to capture by prawn trawling operations, due to its bottom-dwelling habit, poor swimming ability, and presence in trawl grounds; (iv) although improvements in bycatch reduction methods have been implemented in recent years in S.A., assessments of the impact of prawn trawling on Small-tooth Flounder populations in South Australia appear to be inadequate; and (v) there is little information on the population dynamics of this species over space and time, particularly in areas where it is susceptible to capture.

Page Contents

Current Conservation Status

Classified as Least Concern in the Northern Territory (Dept Natural Resources, Environment and the Arts, 2006), but there are no other listings.
 

Distribution

Southern Australia

The species usually occurs across the southern half of southern Australia (southern Queensland through to southern W.A.), but excludes Tasmania (Hutchins and Swainston, 1986; Kuiter, 1993; Gomon, in Gomon et al., 1994; P. Last, CSIRO, pers. comm., 2007). It is also noted that the species was included in a museum checklist of fishes from north-western Australia (Dampier Archipelago) (Hutchins, 2003).
The species is common in some parts of the range (e.g. N.S.W. coastal waters; gulfs region of S.A., and the lower west coast of W.A.).
 

South Australia

Examples of locations where P. jenynsii has been recorded in S.A., include Nuyts Archipelago in eastern Great Australian Bight; northern Spencer Gulf (e.g. Plank Point, Yarraville Shoal, Whyalla and Port Pirie area); south-western Spencer Gulf (e.g. Port Lincoln area); northern metropolitan area of Gulf St Vincent (GSV) (e.g. West Lakes; Outer Harbour); southern metro area of GSV (e.g. Noarlunga, and Onkaparinga Estuary), central (trawled area) of GSV (Richardson, 1999) and other parts of GSV (e.g. Port Giles); and the Coorong estuary (Fairhead et al., 2002a,b; Tanner et al., 2003; Westlake, 1997, cited by Jones et al., 2005; Flinders University data, cited by Hammer, 2006a; Gillanders et al., 2008; Museum of Victoria records, South Australian Museum records, cited in OZCAM database, 2008).
It is noted that in March 2002, during 3 surveys at Outer Harbour (each survey comprising 20 individual beam trawl shots from each of 4 sites, 26 P. jenynsii specimens were recorded in total (Fairhead et al., 2002b; Tanner et al., 2003).
 

Habitat

Small-tooth Flounder live in muddy and sandy habitats, in bays and other coastal waters, including sheltered estuaries, seagrass-lined channels, mangrove forests, and river mouths (Hutchins and Swainston, 1986; Kuiter, 1993, 1996b; Potter et al., 1983, 1990; Gray et al., 1996; Potter and Hyndes, 1999; Amaoka and Hensley, 2001; Travers and Potter, 2002; Young and Potter, 2003c; Melville and Connolly, 2005; Jelbart et al., 2006). The species has also been recorded in coastal lakes (West and Jones, 2001).
In New South Wales, P. jenynsii has also been recorded in normally closed and intermittently open coastal lagoons (e.g. Lake Conjola and Swan Lake) (Pollard, 1994). In the Botany Bay / Port Hacking area, the species has also been recorded in low numbers in stands of the introduced marine alga Caulerpa taxifolia, and in adjacent seagrass beds (York et al., 2006). 
The species is also found further offshore on silty substrates, to about 150m deep (Amaoka and Hensley, 2001). Within prawn trawling depths,  a number of specimens are known from 40m – 50m (Gomon, in Gomon et al., 1994). There are specimens from Spencer Gulf in S.A., from waters ~ 24m to 29m deep (Museum of Victoria data, cited in OZCAM database, 2008).   
During a study of nearshore fishes in south-western Australia, P. jenynsii were recorded mostly in habitat described as “highly sheltered from wave activity, with substrate containing areas of dense seagrass within 50m of the shoreline, and also further offshore” (Valesini et al., 2004). 
 

Notes on the Biology

Growth

The species is large, growing to about 55cm (Hutchins and Swainston, 1986), but commonly smaller, between 20 – 25cm SL (Amaoka and Hensley, 2001).
Two of the largest weights recorded are 1.47kg (being a specimen taken at Ocean Reef Wide in 1986; Allen and Swainston, 19888; Australian Anglers Association - W.A Division, 2005), and 1.356kg (Hutchins and Swainston, 1986; Australian Underwater Federation Inc., 2003). In New South Wales, the maximum size recorded by the N.S.W. Fishing Clubs Association is 0.94kg, being a specimen caught in 1989.
 

Diet

P. jenynsii feeds on epibenthic bony fish, mysids (particularly in summer, according to one study in south-western Australia), polychaete worms, and large crustaceans, such as carid and penaeid decapods, brachyuran crabs etc (Valesini et al., 2004; Platell and Potter, 2006). The dietary composition of P. jenynsii may be influenced by season, and also, the diet of this species undergoes pronounced changes with flounder size (Schafer et al., 2002). In one Western Australian study of 297 individuals of P. jenynsii, crustaceans were present in 44% of the guts examined; bony fish were present in about 65% of the guts examined (Platell and Hall, 2006). and Percentage contributions for other dietary items were 1% molluscs, 1% plant material and less than 1% polychaetes (Platell and Hall, 2006). During that study, the carid Alpheus richardsoni and two penaids prawns (Metapenaeus dallii and Melicertus latisulcatus) collectively contributed 25.6% to the overall dietary volume, while gammarids only contributed 3.6% (Platell and Hall, 2006). Of the fishes, important dietary items in terms of volume were Engraulis australis (12.9%), Pseudogobius olorum (10.1%), Apogon rueppellii (6.9%), Amoya bifrenatus (6.2%) and Argyrosomus japonicus (5.0%). Crustaceans were more important in the diet during summer, and bony fishes during winter (Platell and Hall, 2006).    
 

Reproduction

Flounders live on the sea floor, but are pelagic spawners (Nelson, 2006). P. jenynsii is reported to spawn at sea, but the larvae enter estuaries (e.g. Peel – Harvey estuary in W.A. – Young and Potter, 2003c). Valesini et al. (2004) reported that P. jenynsii is capable of completing the entire life cycle in nearshore waters, indicating that larval dispersal is low. 

Fisheries Information

Commercial – Commonwealth Waters

Small-tooth Flounder is commonly recorded in trawl grounds (Gomon, in Gomon et al., 1994), and specimens caught by small trawls are marketed fresh (Amaoka and Hensley, 2001).
This flounder is a minor part of the bycatch in the Commonwealth-managed SESSF (Southern and Eastern Scalefish and Shark Fisheries) (AFMA, 2002a). The species is listed as a minor part of the bycatch in the otter trawl sub-fishery of the South East Trawl Fishery. During a bycatch monitoring program in 2001, 2kg of P. jenynsii were retained in 1 trawl shot (Wayte et al., 2004). 
 

Commercial – State

P. jenynsii is a commercial species, with the marketing name “Flounder” (Seafood Services Australia, 2003). It is described as “an excellent food fish” (Amaoka, in Froese and Pauly, 2007).  
In New South Wales, commercial catches of “flounder” include species such as P. arsius, P. jenynsii and various species in Ammotretis. Due to difficulty in identifying individual species, all catches are reported as “flounder”. Since the early 1990s, landings of flounder by NSW ocean prawn trawl fishers (all areas) and ocean fish trawl fishers (ocean zones 4-6, State waters) have ranged between 20 to 30t per annum (N.S.W. Department of Primary Industries, 2004).
Small-tooth Flounder is part of the retained bycatch in estuarine fish and prawn hauling fisheries in New South Wales. Pseudorhombus species are caught in areas such as Botany Bay, Port Jackson, Lake Macquarie, and Lake Wooloweyah, St Georges Basin, and the Richmond, Manning, Wallamba, Shoalhaven, Clarence, Hunter, and Hawkesbury rivers (Gray et al., 1990; Liggins et al., 1996; Gray and Kennelly, 2001; N.S.W. Fisheries, 2002). In the Manning River, a survey in 1998 – 1999 recorded between 3,000 and 4,000 Pseudorhombus specimens in the bycatch, with smaller numbers (order of magnitude lower) from the Richmond, Wallamba and Shoalhaven rivers (Gray and Kennelly, 2001). During the early 2000s, the number of locations in which P. jenynsii could be taken as a by-product of the Estuary Prawn Trawl Fishery was regulated, and such areas include Botany Bay, Port Jackson and Hawkesbury River (N.S.W. Fisheries, 2002; New South Wales Government Gazette, Friday, 21st February 2003). The species is also part of the bycatch of estuarine gillnet fishing for flathead in N.S.W. (e.g. Gray et al., 2005)   
Current to 2008, there was no legal minimum size or bag limits for P. jenynsii caught commercially in Queensland (Queensland Department of Primary Industries, 2008), which is at the edge of the geographic range.
Small-tooth Flounder is a commercial species in W.A. (Cappo et al., 1998; Appendix 1 in Malseed and Sumner, 2001a, 2001b). It has also been reported to occur in trawling grounds in north-western Australia (Hutchins, 2003).  
In South Australia, P. jenynsii is one of the flounder species taken by commercial fishers (PIRSA, 2003). Small-tooth Flounder may be a component of the Lakes and Coorong Fishery catch of flounder (most of which is Greenback Flounder Rhombosolea tapirina), but the proportion of the catch that comprises P. jenynsii is not known (Jones et al., 2005). 
When caught in the bycatch of the South Australian Rock Lobster fishery, flounders are permitted to be retained for sale (Sloan, 20003a).
In S.A., Small-tooth Flounder has been recorded from areas in which prawn trawling operates (e.g. GSV / Investigator Strait, Spencer Gulf, and the eastern Great Australian Bight) (e.g. Carrick, 1997; Richardson, 1999; Broadhurst et al., 2000; Museum of Victoria records, cited in OZCAM database, 2008, and see Distribution, above). In the Spencer Gulf prawn trawl fishery, 162 specimens of P. jenynsii were recorded from 32 trawl tows, in a sampling program during the mid 1990s (Carrick, 1997).
 

Recreational

Recreational survey catch statistics (e.g. Henry and Lyle, 2003) 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.
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. DPI, 2004). In a survey of day time recreational fishing at Lake Macquarie from March 1999 to February 2000, Steffe and Chapman (2003) reported that the total catch of P. jenynsii from that area was about 7,422 (± 1,471) specimens, equivalent to about 1.8 tonnes. At Lake Macquarie, the recreational catch of Pseudorhombus flounders (i.e. P. jenynsii and P. arsius combined) is about 10 times that of the commercial catch (Steffe and Chapman, 2003).   
In W.A., the species is considered to be “recreationally important” (Platell and Hall, 2006), and is caught in a number of estuaries, including the Swan, in the metropolitan area. During a 12-month survey of recreational fishing in the Swan-Canning estuary basin in 1998-99 (Malseed and Sumner, 2001a), 775 (SE = 136) flounders in the genus Pseudorhombus were kept, and 765 (SE = 123) were released, by boat-based fishers. Small numbers were caught by shore-based fishers (Malseed and Sumner, 2001).  The proportion of the catch that was P. jenynsii (compared with P. arsius) is not known. During a 12-month survey of recreational fishing in the Peel-Harvey estuary basin in 1998-99 (Malseed and Sumner, 2001b), 86 (SE = 17) flounders in the genus Pseudorhombus were kept, and none were released, by boat-based fishers. Small numbers were caught by shore-based fishers (Malseed and Sumner, 2001b). The proportion of the catch that was P. jenynsii (compared with P. arsius) is not known. Small quantities of Pseudorhombus flounders are also caught by fishers in the Leschenault Estuary (Malseed et al., 2000), and Walpole / Nornalup Inlet, in which a recreational fishing study from December 2002 – November 2003, estimated that about 99 (SE = 98) Greenback Flounders were caught and kept by boat-based fishers in that Inlet (Smallwood and Sumner, 2007). In W.A., the legal minimum size is 25cm for all flounder species, and there is 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).
 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).
For recreational fishers in South Australia, there is a daily bag limit of 20 flounder (all species) and a boat limit of 60, but there is no legal minimum size (PIRSA, 2008a, 2008b). P. jenynsii is one of the flounder species taken by recreational fishers in S.A. (PIRSA, 2003). 
P. jenynsii is taken by spearfishers. One of the largest weights recorded is a specimen of 1.300kg, taken at Yanchep in W.A., in 1979 (Australian Underwater Federation Inc., 2003). 
 

Vulnerable Characteristics of the Species, and Threatening Processes

Benthic fishes in general have limited mobility, more localised reproduction than most pelagic species, and limited opportunity for population dispersal, all of which can increase the vulnerability of populations to decline.
The combined effects of commercial and recreational fishing, in areas where these are high (e.g. N.S.W.), may be a threatening process.
Prawn trawling may be a threatening process to some populations of this species. P. jenynsii is found in the prawn trawling grounds in S.A. (e.g. lower central GSV / Investigator Strait, central Spencer Gulf, and off the Anxious Bay area in the eastern Great Australian Bight). P.jenynsii is listed as being highly vulnerable to capture by prawn trawling operations in Spencer Gulf, due to its bottom-dwelling habit, poor swimming ability, and presence in trawl grounds (Carrick, 1997; PIRSA, 2003). The species has also been recorded amongst the top 5 scalefish species in the Gulf St Vincent prawn trawl fishery (Broadhurst et al., 2000). According to PIRSA (2003), P. jenynsii may be considered at “higher risk” than some other bycatch species in the Spencer Gulf Prawn Trawl Fishery (SGPTF), because it is also caught by other sectors (commercial scalefish fishers, and recreational fishers). In the SGPTF, prior to the development of hopper / conveyor systems by the prawn fleet, a statistically significant reduction in abundance of the Small-toothed Flounder (Pseudorhombus jenynsii) was detected in controlled field experiments (Carrick, 1997, cited by PIRSA, 2003). Furthermore, at that time (1990s), comparison of replicate or adjacent pairs of fished versus unfished (closed) areas demonstrated significantly lower densities of flounder at fished areas compared to paired controls, and this supported other research pointing to a “large localised impact” of trawling on the species. However, PIRSA (2003) reported that the impact study was undertaken prior to the development of hopper / conveyor systems in the prawn fleet in Spencer Gulf, and that recent field studies have indicated higher survival of flounders (e.g. the commonly caught species Pseudorhombus jenynsii) with hopper/conveyors systems, compared with the previously used sorting equipment. However, Australian Government DEH (2004b) reported that further work is required to confirm this assumption (see Management Notes).
Flounder species in general are defined as “Category 2” fish in Western Australia, with a “medium risk” of over-exploitation. Category 2 fish species generally mature at two to three years old, are of moderate abundance, are highly targeted, and/or often utilise estuarine and inshore habitats extensively (Department of Fisheries, 2004).
In a draft ecological risk assessment report for the South East Trawl Fishery (Wayte et al. 2004), 3 “productivity attributes” and 5 “susceptibility attributes” were used to classify P. jenynsii as being a “medium risk” species in terms of potential population impacts from trawling.
Small-tooth Flounder occurs in coastal areas such as estuaries and shallow sandy bays, and populations may thus be vulnerable to decline in coastal areas where impacts degrade the habitat. For example, there are few pristine or near pristine estuaries remaining in South Australia, and most are subject to numerous impacts (see Bucher and Saenger, 1989; Lewis et al., 1998; Barnett, 2001; GeoScience Australia, 2001; Bryars, 2003; Baker, 2004; Gillanders et al., 2008). Also in other States, this species occurs in polluted bays and estuarine areas (e.g. the Derwent estuary in Tasmania, in which point sources of pollution include 10 sewage treatment plants and two large industries (paper mill and smelter), coupled with diffuse sources from urban runoff; waste / rubbish tips and contaminated sites; catchment inputs carried by the Derwent and Jordan Rivers; atmospheric contributions and wastes associated with shipping operations, port facilities and marinas (Green and Coughanowr, 2003). Some pollutants are also derived from contaminated sediments within the estuary itself. Contaminants associated with these various sources include pathogens, nutrients, organic matter, silt and gross solids, wood extractives such as resin acids, and a range of toxicants including heavy metals and hydrocarbons (Green and Coughanowr, 2003).
Other than for R. tapiria (see synopsis), there are few 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).
A study in N.S.W. (Pollard, 1994) indicated that this species was more abundant in a permanently open coastal lagoon than in two others which were intermittently open. This may indicate the vulnerability of this species to reductions in flow volume in estuarine areas. 
Pseudorhombus jenynsii 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).
 

Research Requirements

There is little information on population sizes, biology and population dynamics of this species.  
Assessment of spatial and temporal variation in flounder bycatch in prawn trawl fisheries in S.A. should be undertaken where possible. Dixon et al. (2005) provided examples of bycatch monitoring in Spencer Gulf in which it was not possible to determine spatial or temporal variation in the flounder catch due to the timing of the bycatch surveys, and other factors.
 

Management Requirements

Documentation and quantification of flounder bycatch in fisheries across the geographic range is required.  For example, status of flounder stocks in N.S.W. is uncertain, because the species composition of the catch needs to be determined. Collection of biological and fishery data for the important commercial species of flounder is considered to be a high priority (N.S.W. Department of Primary Industries, 2004).
In S.A., a system should be developed for the ongoing collection and monitoring of bycatch data from the Gulf St Vincent Prawn Fishery and the West Coast Prawn Fishery (as currently occurs in the Spencer Gulf Prawn Trawl Fishery), sufficient to enable identification of long-term trends in bycatch (Australian Government DEH, 2004b).
Measures (such as further improvements in net design) to reduce the bycatch of benthic fish species in all trawl fisheries should be implemented (see Management Notes). This is particularly required in areas where bycatch is high (e.g. New South Wales, and S.A.).
Assessment of the sustainability of catches in the N.S.W. commercial fishery is required.
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.
Generally required is ongoing management and mitigation of multiple impacts that have reduced the quality of estuarine habitats in S.A. and other southern States. This includes protection of shallow coastal bays from land-based discharges, and, where possible, from coastal activities (e.g. dredging, and aquaculture developments) that can reduce benthic habitat quality in such bays.  
 

Management Notes

It is noted that prawn fisheries in southern Australia have made significant efforts during the past decades to reduce the bycatch of finfish species. Examples for Spencer Gulf and Gulf St Vincent include the spatial and temporal organisation and “real time” management of the fishing fleet in some areas (e.g. Spencer Gulf) to minimise capture of undersized prawns and bycatch species, and developments in gear design to reduce bycatch, such as square-mesh cod-ends, bycatch chutes, hopper/conveyor systems, and the fitting of exclusion devices (e.g. MacDonald, 1998; Carrick, 1997; Broadhurst et al., 1999; South Australian Prawn Industry Association web site, 2000; PIRSA, 2003). PIRSA (2003) reported that field studies have indicated that survival of flounders (e.g. the commonly caught species Pseudorhombus jenynsii) is higher with hopper/conveyors systems, compared with the previously used sorting equipment. However, Australian Government DEH (2004b) reported that further work is required to confirm this assumption.
P. jenynsii is an indicator species in ecological impact assessment of the Spencer Gulf Prawn Trawl Fishery, due to its high vulnerability to capture, distribution pattern, sufficient statistical power to detect trends, and relatively long lifespan (>4 years) (PIRSA, 2003). According to PIRSA (2003), catches are to be recorded by independent trawl by-catch monitoring systems, as well as fishers’ logbook entries. The aim is to compare population levels and size of flounder in open and closed areas, and to provide information on trends in numbers and size. Independent observers are supposed to validate logbook entries, to enable an estimation of take in the fishery, and consequently to provide “a more conclusive level of data on which to base further assessment on the risk to flounder from prawn trawling” (PIRSA, 2003). The use of the species as an indicator aims to determine “how well the fishery responds using appropriate management tools -  particularly operational practices which have potential to reduce by-catch mortality, and ensure that resource sharing between different user groups” (PIRSA, 2003). Dixon et al. (2005) provided examples of flounder bycatch studies in Spencer Gulf, in which the number and weight of “flatfish” (flounder and sole) were recorded sporadically between 1994 and 2002. Species-specific data were not reported, but it is likely that the majority of the flounder catch comprised P. jenynsii. During 1997 to 2000, length and weight measurements were taken from flounder species in the Spencer Gulf prawn trawl bycatch. Total length of flounder ranges from 7cm – 39cm, with a modal size class of 19cm – 21cm (Dixon et al., 2005). The distribution was right-skewed, increasing sharply from 16cm – 21cm (Dixon et al., 2005). 
Broadhurst et al. (2000) provided examples of prawn trawl gear experiments, in which the use of “momoi” trawl body (1.7-mm-diameter, 30-ply, polyethylene twisted twine) reduced the number of P. jenynsii specimens taken in prawn trawl bycatch in Gulf St Vincent, compared with the control trawl body, but the results were not statistically significant.
 

Other Information

There is a lot of variation in the shape and colour patters of P. jenynsii from different regions; hence these might represent a complex of very similar species, but further examination is required of specimens from across the range (Gomon, in Gomon et al., 1994).  
During the past two decades, investigations have been undertaken into aquaculture of species such as P. arsius and P. jenynsii (e.g. Treadwell et al., 1992). In W.A., Pseudorhombus species are considered to have potential for culture in sea cages or land-based tanks / ponds (Kendrick et al., 2002). P. jenynsii is listed as an aquaculture species of  “secondary importance”. Proposed sites of interest for aquaculture including Ningaloo Coast, Shark Bay Coast, Central West Coast, Leeuwin-Naturaliste Coast, South Coast, and Eucla Coast (Makaira Pty Ltd and Ecologia Environmental Consultants, 1997).