A small, cylindrical fish with a rounded head, bulbous cheeks and a small mouth. Maximum size ~60 mm, commonly <45 mm. The gape extends to just past the anterior margin of the eye in females, and to mid-eye or further back in males. There are two dorsal fins, the caudal fin is oval, and the pelvic fins are joined to form a disc-shape. Scales are present on the nape and opercula. The head and body is light-brownish to yellowish-brown or grey, fading to white on the ventral surface. A series, usually of 5–6 dark, roughly rectangular blotches are present on the back from the nape to the caudal peduncle, and there is another series of mid-lateral blotches on the sides. The anal fin may have a blue edge, the dorsal fins are barred, and the first dorsal fin may have a blue spot.
The Western blue-spot goby is really an estuarine generalist and occupies brackish estuaries and associated freshwater streams and lakes. It is benthic, burrowing and usually recorded over mud or rock substrates, occasionally in weedy areas.
It spawns about 150 eggs in dense aquatic vegetation in spring in the upper reaches of estuaries, and the male guards and fans the eggs. Females can mature at lengths as small as 15 mm, with all mature by 36 mm. This short-lived species breeds twice per year, with spawning in a Western Australian estuary peaking in mid-October and mid-March, and most spawning individuals then dying. The larval fish grow rapidly, but then growth effectively ceases over the cooler months (mid-May to mid-September) before growth resumes in spring, with females growing faster than males in this second growth period. In an estuary in Western Australia, the diet consisted mainly of benthic crustaceans and algae and in a small Vic estuary the diet was dominated by detritus and microcrustaceans such as ostracods, amphipods and cladocerans.
This goby is a common and widespread estuarine species in coastal streams of SA and WA. In the Basin it is known only from the Lower Lakes (Alexandrina and Albert) and associated wetlands, where it exists as largely landlocked populations. Towards the end of the Millennium Drought the species boomed in the Lower Lakes as freshwater flows declined and salinity started to increase. Numbers then declined again following the breaking of the drought in 2010 and decreasing salinity. Similarly in the Coorong, as with other small-bodied estuarine species, numbers declined as the drought intensified and the normally brackish water became hypersaline. This species has not been collected as part of the Sustainable Rivers Audit (2004–2013) or the MDB Fish survey (2014/15–2021/22).
None known, but the prolonged lack of freshwater inflows to the Coorong during the Millennium Drought and resultant hypersalinisation, were associated with declines in this species.
Allen et al. 2002; Becker & Laurenson 2007; Bice et al. 2016a, 2017, 2020a; Cadwallader & Backhouse 1983; Gill & Potter 1993; Gill et al. 1996; Humphries & Potter 1993; Larson & Hoese 1996b; Smith et al. 2009; Wedderburn & Hammer 2003; Wedderburn et al. 2014; Wise 2005; Zampatti et al. 2010, 2011.
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