© 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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 Large-mouth Goby / Largemouth Goby

Family Name:	Gobiidae
Scientific Name:	Redigobius macrostoma (Günther, 1861)
Recommended Status in S.A:	Data Deficient, possibly Rare D(i) or E(ii) (for S.A. only)
Rationale:  Large-mouth Goby is included here because (i) South Australia is at the edge of the geographic range; (ii) the species is found over a narrow depth range, and to date, is known in S.A. from few records, mainly in Gulf St Vincent; (iii) gobies are typically benthic nest spawners and egg guarders, and hence populations may be vulnerable to localised / site specific impacts; (iv) R. macrostoma is found mainly in estuaries, which are few in number in S.A., and most are significantly degraded; and the estuarine systems in Gulf St Vincent in which this species has been reported to date, are subject to numerous, ongoing threatening processes.

Page Contents

Current Conservation Status

There are no official listings for this species, but the Large-mouth Goby has been described as rare in southern waters (Hoese and Larson, in Gomon et al., 1994).
 

Distribution

South-Eastern Australia

The species occurs mainly in southern Queensland, N.S.W., and Victoria (Hoese and Larson, in Gomon et al., 1994; Australian Museum records, Museum of Victoria records, cited in OZCAM database, 2007), although the distribution extends to north-eastern Tasmania, and South Australia.
 

South Australia

Previously, the western limit was recorded as Glenelg River, near the Victoria / South Australian border (Hoese and Larson, in Gomon et al., 1994; Kuiter, 1996b; Larson, 2001); however the species extends into central S.A., and has been recorded at a number of locations in eastern Gulf St Vincent, including the Onkaparinga Estuary in southern metropolitan Gulf St Vincent (Adelaide University data, cited by Hammer, 2006a); Patawalonga Creek and lakes (Gillanders et al. 2008); West Lakes (Cheshire et al., 2002) and the Port River, in northern metropolitan GSV (Hammer, 2005b).
 

Habitat

Most commonly found in seagrass beds, and on sand and rock bottom in sheltered estuaries and harbours (Kuiter, 1993, 1996a, 1996b; Hoese and Larson, in Gomon et al., 1994; Classon and Booth, 2002), but also recorded in coastal lakes and the lower reaches of rivers and streams (e.g. in N.S.W. - Gray et al., 1996, and West and Jones, 2001; Museum of Victoria records A3517 and A18378).
In N.S.W., the species has been recorded in shallow Zostera seagrass and estuaries (e.g. Gray et al., 1996), and in the freshwater / brackish eelgrass Vallisneria (e.g. West and King, 1996), and abundantly in Posidonia seagrass in shallow marine areas (McNeill and Bell, 1992; Ferrell et al., 1993). Large numbers have been recorded in some of the coastal lakes in New South Wales (e.g. West and Jones, 2001).  In New South Wales the species is also known from mangrove-lined creeks (e.g. Bell et al., 1984; Mazumder, 2004). Also in New South Wales, York et al. (2006) reported R. macrostoma in beds of the invasive alga Caulerpa taxifolia, adjacent to seagrass beds, and numbers found in Caulerpa were comparable to (but slightly higher than) those found in Zostera seagrass.
Large-mouth Goby is also found on rocky reefs, jetty piles or bridges across lake entrances, in small aggregations (Hoese and Larson, in Gomon et al., 1994; Kuiter, 1996a).
In Queensland, the species has been recorded in soft bottom habitats (e.g. Meager et al., 2005).
 

Notes on the Biology

Large-mouth Goby grows to around 5cm (Kuiter, 1993, 1996b; Hose and Larson, in Gomon et al., 1994).
Members of the family are typically nest spawners, with males guarding the eggs (Hoese, 1998).
Larvae settle to a benthic existence when between 6.7 and 8.5mm body length (Neira et al., 1998, cited in Froese and Pauly, 2007).
 

Fisheries Information

Large-mouth Goby is little used by anglers; however it is sometimes caught in nets and traps, for bait (Classon and Booth, 2002).
The species has been recorded in the bycatch of the Estuary Prawn Trawl fishery in N.S.W (New South Wales Fisheries, 2002).
 

Vulnerable Characteristics of the Species and Threatening Processes

The species is associated with estuaries and other shallow nearshore habitats. 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). The fact that most population centres in Australia are located within close proximity to coastal and/or estuarine environments means that estuarine habitats and their associated communities are often vulnerable to the effects of habitat degradation, and overexploitation by humans (Pogonoski et al., 2002). There are few pristine or near pristine estuaries remaining in South Australia and most are subject to numerous impacts, with prime examples including the Port River – Barker Inlet Estuary, the Onkaparinga, and the Coorong – Murray Mouth (see Bucher and Saenger, 1989; Lewis et al., 1998; Barnett, 2001; GeoScience Australia, 2001; Bryars, 2003; Baker, 2004; DEH, 2005; EPA – S.A., 2006; Gillanders et al., 2008).
Populations of estuarine goby species in degraded areas such as the Port River – Barker Inlet system may be vulnerable to extirpation from further habitat loss, fish kill events, and/or treatment methods to control introduced organisms (Hammer, 2006b).
In N.S.W., during a comparison of fish assemblages in an area with a tidal floodgate, and an un-gated reference area, Kroon and Ansell (2006) reported significant higher numbers of Large-mouth Goby in the un-gated area, indicating that flood mitigation structures may have an impact on estuarine fish populations in some areas.  
Gobies are benthic nest spawners and egg guarders, a population characteristic that increases their vulnerability to site-specific habitat impacts.
 

Research Requirements

In South Australia, surveys are required to better determine the distribution and relative abundance of this species in GSV, and in other parts of the State.
When the less commonly known goby species are recorded in surveys, fish taxonomy experts should be sought to provide species-specific determinations. Voucher specimens and/or photographs should be taken.
Genetic studies are required to determine whether this species is native within S.A. (Hammer,  2006b).
 

Management Requirements

An assessment of the possible impacts of estuarine degradation in S.A. on Large-mouth Goby populations is required. Determination of the impacts of reduced water quantity and quality on goby populations will help to better determine the conservation status of these species in S.A., and will assist with the development of recovery plans for small estuarine fish species.
Ongoing programs to protect and restore estuarine function may benefit small, site-associated estuarine species such as Large-mouth Goby. 
 

Other Information

R. macrostoma is the only species of Redigobius found on the south coast of Australia. The genus is Indo-Pacific, and comprises about 15 species, mostly found in tropical mangroves and rivers (Kuiter, 1996b).