© 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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Bass Strait Flounder

Family Name:	Bothidae
Scientific Name:	Arnoglossus bassensis Norman, 1926
Recommended Status in S.A:	Data Deficient
Rationale:  The species is included here because (i) eastern South Australia is at the edge of the geographic range of Arnoglossus bassensis; (ii) it is a little known species, with few published records, and little information about its relative abundance, biology, or population dynamics across the range; (iii) the species is recorded in low abundance as bycatch in prawn trawl fisheries in S.A.; however, bycatch species identification and quantification are insufficient in the S.A. prawn fishery in Gulf St Vincent, hence the previous and current extent of capture of Bass Strait Flounder in prawn trawl in S.A. is not known, and no assessment of potential population impacts has been undertaken; (iv) there is little indication of the total commercial and recreational catch of this species, in relation to its relative abundance and distribution in S.A., and (v) the species occurs in coastal areas, including estuaries, and may be vulnerable to impacts from habitat damage in some nearshore areas, but there are no species-specific data.

Page Contents

Current Conservation Status

(No listings known)

Distribution

Southern Australia

The species occurs along the south-eastern coast of Australia, including Tasmania and Bass Strait, Victoria and eastern South Australia, with Narooma in New South Wales as the published north-eastern limit (Gomon, in Gomon et al., 1994).
Flinders Island in Bass Strait is the type locality (Eschmeyer, 2001).
During a survey of estuaries around Tasmania, A. bassensis was recorded in low abundance in estuaries such as the Huon, and also the central north of Flinders Island (Edgar et al., 1999). 

South Australia

Examples of locations in S.A. where the species has been recorded include far northern Gulf St Vincent; northern, central and central-western Spencer Gulf; northern Kangaroo Island / central Investigator Strait area, and eastern end of Kangaroo Island (Carrick, 1997; BMNH records, cited in Anonymous, 1999; Australian Museum records, S.A. Museum records, cited in OZCAM database, 2008).

Habitat

Arnoglossus bassensis occurs on sandy bottoms, in waters from a few metres deep (or 10m deep, according to Kuiter 1993, 1996b) to around 70m or more (Gomon, in Gomon et al., 1994; Kuiter, 1996b).
The Bass Strait Flounder is common in estuaries (Kuiter, 1993, 1996b).  

Notes on the Biology

The species grows to at least 25cm (Kuiter, 1993; Gomon, in Gomon et al., 1994).
Flounders live on the sea floor, but are pelagic spawners (Nelson, 2006).

Fisheries Information

For flounders, no species-specific commercial and recreational fishing data are available for this report; however some general points are listed below:

Commercial

Gomon (in Gomon et al., 1994) and Kuiter (1996b) reported that the species does not reach a large enough size to be of commercial importance.
It is noted that flounder species (unspecified) are taken in minor quantities by commercial fishers in southern Australian States, including S.A. (see introductory section of this chapter).
When caught in the bycatch of the South Australian Rock Lobster fishery, flounders are permitted to be retained for sale (Sloan, 20003a).
Arnoglossus bassensis has been recorded as a very minor component of the bycatch in the prawn trawl fishery in Spencer Gulf, South Australia. For example, 1 Bass Strait Flounder was recorded from 32 trawl tows, in a sampling program during the mid 1990s (Carrick, 1997).
There are museum records of specimens taken as bycatch by prawn trawlers in Spencer Gulf and Investigator Strait waters in S.A. (South Australian Museum records, cited in OZCAM database, 2008).

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 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 (all species) in 2000/01 of 21 tonnes was double the size of commercial catch, indicating the importance of the recreational component of this fishery (Henry and Lyle 2003, cited by Lyle et al., 2004).
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. There is no minimum legal size in S.A. (PIRSA, 2008a, 2008b). 

Vulnerable Characteristics of the Species and Threatening Processes

South Australia is at the edge of the species’ range.
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.
Arnoglossus bassensis occurs in relatively shallow waters, including estuarine areas, and may therefore be vulnerable to coastal impacts in some areas. 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 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). A summary of many of the impacts in shallow coastal bays in S.A. is provided in Baker (2004).
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).
Flounders are vulnerable to capture in prawn trawls, due to their benthic nature, existence in the same habitats as prawns are found, and their poor swimming ability (Carrick, 1997; PIRSA, 2003). There is evidence that the Bass Strait Flounder is taken as bycatch in the Gulf St Vincent and Spencer Gulf prawn fisheries, as detailed above, but there is no information on the extent to which this species is captured. Mortality due to trawling may be a threatening process for some of the flounder species of lesser abundance in S.A., but no species-specific data are available.
Tanner (2003 and 2005) discussed the impacts of prawn trawling on habitats and benthos in Gulf St Vincent, and flounders live in such trawled habitat.

Research Requirements

More information is required on the current geographical distribution of Bass Strait Flounder in South Australia. The species is little known in this State, with few published records.
There is little information on population sizes, biology, and population dynamics of this species.  
Where possible, flounders in prawn trawling bycatch from Gulf St Vincent, Spencer Gulf and the West Coast of S.A. should be recorded, with data analysed and monitored to determine the presence and relative abundance of this species over time.  

Management Requirements

Documentation and quantification of flounder bycatch in fisheries across the range is required.
As indicated in Research Requirements above, 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; Dixon et al., 2005).
Measures (such as further improvements in net design) to reduce the bycatch of benthic fish species in all trawl fisheries are recommended (see Management Notes).

Management Notes

Measures (such as improvements in net design) to reduce the bycatch of benthic fish species in all trawl fisheries are recommended. 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. 
Generally required is the ongoing management and mitigation of the 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 (such as dredging, and aquaculture developments) that can reduce benthic habitat quality in such bays.