© 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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Pikehead Hardyhead

Family Name:	Atherinidae
Scientific Name:	Kestratherina esox (Klunzinger, 1872)
Recommended Status in S.A:	Data Deficient
Rationale:  The species is included here because (i) South Australia is at the edge of the geographic range; (ii) the species apparently occurs over a narrow depth range; (iii) habitat damage and decline in water quality may be potential threats to populations of K. esox, given that the species occurs in estuaries and shallow, sheltered coastal bays over a narrow depth range. In South Australia, many of the estuarine and shallow bay habitats are subject to numerous physical, chemical, biological, and combined impacts, but there are no data on the specific effects of decline in habitat quality on hardyhead species. The Pikehead Hardyhead is listed here as Data Deficient, because there are very few records, and surveys in shallow bays and estuaries are required to determine the distribution and relative abundance of K. esox in South Australia.

Page Contents

Current Conservation Status

No listings known

Distribution

Southern Australia

The species has a southern Australian distribution, from Ceduna / eastern Great Australian Bight in South Australia, to Western Port Bay in Victoria, Bass Strait islands and Tasmania (Paxton et al., 1989; Ivantsoff, in Gomon et al., 1994; Edgar et al., 1999).
The species is considered to be most common in southern Tasmania (Ivantsoff, in Gomon et al., 1994), and in listed as an indicator species for the Tasmanian Province (IMCRA Technical Group, 1996). Examples of locations in Tasmania where the species has been recorded include Tamar River estuary (northern Tasmania), Derwent estuary, Huon River and Port Esperance region, Bruny Island, D’Entrecasteaux Channel, Frederick Henry Bay and various other shallow bays and associated beaches off south-eastern Tasmania (Jordan et al., 1998; DPIF Tasmania, 1997; Edgar et al., 1999; DPIWE, 2002).
Port Phillip Bay in Victoria is the type locality (Eschmeyer, 2001). A study by J. Hindell (cited by FRDC, undated; Hindell, 2006), showed that the species was one of the two most numerically dominant piscivorous fishes at two sampled sites in Port Phillip Bay. There are numerous museum specimens from sites in Port Phillip Bay (Museum of Victoria records, cited in OZCAM database, 2007).

South Australia

Examples of locations in S.A. where the species has been recorded include the Ceduna area and Venus Bay, both on the western side of Eyre Peninsula (eastern Great Australian Bight); Spencer Gulf; north-eastern Kangaroo Island (e.g. Bay of Shoals; American River estuary and Cygnet River); locations in north-eastern Gulf St Vincent, such as Light River delta, Gawler River, Outer Harbour, and the Port River – Barker Inlet estuary (where it was recorded in very low numbers during an estuarine fish sampling program); and Onkaparinga Estuary in the southern metropolitan area of GSV (Glover, 1979; Paxton et al., 1989; Ivantsoff, in Gomon et al., 1994; Jones et al., 1996; Edgar, 2000; Fairhead et al., 2002b; Flinders University data, cited by Hammer, 2006a; South Australian Museum records, cited in OZCAM database, 2007; Gillanders et al., 2008).

Habitat

Kestratherina esox is found in inshore waters (Paxton et al., 1989). It occurs in shallow lagoons and protected bays (e.g. Jordan et al., 1998), but is less common in estuaries (Ivantsoff, in Gomon et al., 1994). It is frequently found in or near beds of seagrass such as Heterozostera nigricaulis (Edgar, 2000), in shallow waters of less than 50cm depth (Ivantsoff, in Gomon et al., 1994; Jordan et al., 1998). In various parts of south-eastern Tasmania, K. esox has been recorded in nearshore beach and lagoon habitats (Jordan et al., 1998).
In Victoria, the species is common in seagrass beds in Western Port Bay (EPA of Victoria, 1996, cited by Plummer et al., 2003) and Port Phillip Bay (Hindell et al., 2000; Hindell, 2006). K. esox has also been recorded in estuarine areas in Victoria, including the catchments of polluted urban rivers such as the Werribee (DSE Aquatic Fauna database, cited in Sherwood et al., 2005).
In Corner Inlet in Victoria, the species has been recorded as being relatively common in mangrove habitat (Jenkins and Hindell, FRDC project No. 2001/036, cited by Plummer et al., 2003). In Western Port Bay and Corner Inlet, the species is more commonly recorded in mangroves than in un-vegetated mudflats (Hindell and Jenkins, 2004).
K. esox has also been recorded using saltmarsh flats in Victoria (Crinall and Hindell, 2004).

Notes on the Biology

The Pikehead Hardyhead grows to around 15cm, and is the second largest hardyhead in Australian waters (Ivantsoff, in Gomon et al., 1994).
The species feeds mainly on small benthic and epibenthic fish (particularly new recruits and juveniles), which can comprise more than 80% of the diet, according to a study by Hindell et al. (2000). Pikehead Hardyhead also eats amphipods, copepods, and small decapods (Ivantsoff, in Gomon et al., 1994). A study in Victoria showed that K. esox eat more fish prey in summer and early autumn than in winter and spring (Hindell et al., 2000, cited in FRDC, 2003a).
In one study, the reproductive season of K. esox was shown to occur at a different time of the year than that of the Short-snout Hardyhead, in areas where the two species are found together (Ivantsoff, in Gomon et al., 1994).

Fisheries Information

K. esox is not known to be targeted for the baitfish market in S.A., and there is unlikely to be any significant capture of this species in S.A. due to its low numbers, in comparison to the highly abundant hardyhead species, such as Atherinosoma microstoma.
There are records of the species being captured during commercial fishing in Bass Strait (Anon., 2002b).

Threatening Processes

Potential threats to populations of K. esox relate to habitat damage and decline in water quality, given that the species occurs in very shallow lagoons and protected bays, particularly near seagrasses, but also in mangrove habitat. In South Australia, coastal habitats in some areas, particularly shallow, seagrass-dominated bays and estuaries, as well as mangrove stands, are subject to numerous physical, chemical, biological, and combined impacts (e.g. upper Spencer Gulf, upper Gulf St Vincent, and parts of western Eyre Peninsula / eastern Great Australian Bight – see Baker, 2004, for a summary).

Research Requirements

Surveys in shallow bays and lagoons are required to determine the relative abundance of this species in S.A., with verification of specimens at the South Australian Museum. It is possible that in the various surveys, Kestratherina species could be mistaken for other species, because some of the hardyhead species in southern Australia are very similar in appearance, even those in different genera (e.g. Leptatherina presbyteroides).

Other Information

Kestratherina, the genus to which this species belongs, contains only two members, both restricted to southern Australia (Ivantsoff, in Gomon et al., 1994).
K. esox has been recorded in a number of protected areas in Victoria, such as Corner Inlet (Plummer et al., 2003).