© 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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Elongate Flounder / Elongated Flounder

Family Name:	Pleuronectidae
Scientific Name:	Ammotretis elongatus McCulloch, 1914
Recommended Status in S.A:	Data Deficient
Rationale:  The species is included here because A. elongatus (i) might have a geographically limited distribution in S.A., with current records known from the Gulfs region and surrounds; (ii) is reported to have a narrow depth range, based on currently known records; (iii) is associated with estuaries for part of the life cycle; 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; (iv) is subject to mortality due to bycatch in prawn trawling; (v) has been recorded as a minor component of prawn trawl catches in S.A., but there is little indication of the total commercial and recreational catch of this species, nor any data on potential impacts; (vi) there is little existing information about the relative abundance, biology and population dynamics of this species across its range.

Page Contents

Current Conservation Status

(No listings known)
 

Distribution

Southern Australia

The species is found mainly in southern W.A. and S.A. (Hutchins and Swainston, 1986), but is reported to extend eastwards to eastern Victoria and Goose Island in Tasmania (Edgar, 2000).
Elongate Flounder is abundant in south-western Australia (Valesini et al., 2004; Hourston et al., 2004).
 

South Australia

Examples of locations in S.A. where A. elongatus has been recorded include Point Lowly and other locations in northern Spencer Gulf; Port Victoria area in eastern Spencer Gulf; Point Turton in south-eastern Spencer Gulf; far northern Gulf St Vincent; Port Julia and Sheoak Flat (near Port Vincent), in western Gulf St Vincent; Onkaparinga Estuary in the southern metropolitan area of GSV (Flinders University data, cited by Hammer, 2006a); Port Giles (Fairhead et al., 2002a) and Edithburgh, in south-western GSV / “heel” of Yorke Peninsula; Investigator Strait (the type locality – McCulloch, 1914), and Kangaroo Island (British Museum of Natural History data, 1925, cited by Anonymous, 1999; Australian Museum records, Museum of Victoria records, cited in OZCAM database, 2008).
 

Habitat

Elongate flounder is found on sandy and silty bottoms in estuaries and coastal bays (Hutchins and Swainston, 1986). Lenanton (1982) and Valesini et al. (2004) reported that Elongate Flounder does not spend its entire life cycle in estuaries, but utilises such habitat as a nursery area. During a study in south-western Australia during the early 2000s, A. elongatus was recorded (in low densities of less than 1 per 100m²) in various nearshore habitats, sheltered from wave activity or moderately expose to it, with dense, sparse or no seagrass cover (Valesini et al., 2004). In other parts of south-western W.A., A. elongatus has been recorded in shallow estuaries (e.g. Loneragan et al., 1986); nearshore seagrass beds (Hyndes et al., 2003; Hutchins, 2005), also on soft bottom habitats in mainland bays (Hutchins, 2005), and in sandy surf zones (Ayvazian and Hyndes, 1995).    
A. elongatus has been recorded in waters as shallow as 1m (Museum of Victoria record, cited in OZCAM database, 2007). The published depth range is 0m – 20m (Edgar, 2000).
 

Notes on the Biology

Growth

A. elongatus grows to about 22cm (Hutchins and Swainston, 1986).
 

Diet

Elongate Flounder eats small benthic crustaceans (Valesini et al., 2004), such as small cumaceans and amphipods, which live on the substrate surface, and are a major part of the diet (Hourston et al., 2004). Elongate Flounders also eat polychaete worms, and foraminifera (Hourston et al., 2004).    
 

Reproduction

Flounders live on the sea floor, but are pelagic spawners (Nelson, 2006).
 

Fisheries Information

Commercial

Little species-specific commercial fishing data are available. However, it is noted that flounder species (unspecified) are taken in minor quantities by commercial fishers in southern Australian States (see section above, on Commercial Fishing for flounders as a group).
Commercial catches of unspecified flounders in W.A. (which may include A. elongatus) are listed at the beginning of this chapter.
A. elongatus is a minor component of the bycatch in the prawn trawl fishery in Spencer Gulf, South Australia. For example, 3 Elongate Flounder were recorded from 32 trawl tows, in sampling program during the mid 1990s (Carrick, 1997). There are no data available on the bycatch of this species in the prawn fisheries in other parts of South Australia.  
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) 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).
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. (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

Elongate Flounder might have a geographically limited distribution in S.A., with current records known from the Gulfs region and surrounds.
To date, Elongate Flounder has been recorded over a narrow depth range (of 20m). A summary of many of the impacts in shallow coastal bays in S.A. is provided in Baker (2004).
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.
A. elongatus occurs in relatively shallow waters, including estuarine areas, and may be susceptible to population impacts due to decline in estuarine habitat and water quality, but there are no species-specific data. 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).
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). Elongate Flounders are taken as bycatch by prawn trawlers, but the extent to which this practice impacts upon populations is not known for this report (see below, on Research Requirements). 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. It is noted, however, that one study reported A. elongatus as only a minor component of the prawn trawl bycatch in Spencer Gulf (i.e. Carrick, 1997), hence threat of impact on this species from trawling may be low, at least for that gulf. 
Tanner (2003 and 2005) discussed the impacts of prawn trawling on habitats and benthos in Gulf St Vincent and Investigator Strait, and the species has been recorded in that area.   
The combined effects of commercial and recreational fishing may be a threatening process, but there are no species-specific data. 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).
 

Research Requirements

More information is required on the current geographical distribution, habitat requirements and depth range of Elongate Flounder in South Australia. The species is little known in this State, with few published records.
There is very little information on the population sizes, biology, and population dynamics of this species.  
There is little indication of the total commercial and recreational catch of this species, in relation to its relative abundance and distribution, including South Australia.
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 geographic 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 improvements in net design) to reduce the bycatch of benthic fish species in all trawl fisheries should be implemented (see Management Notes, below).
An assessment of the sustainability of fishing this species commercially (e.g. in W.A.) is required.
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. 
 

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.