Atherinomorus vaigiensis
Small silver schooling fish logged around Western Australia, staying comfortable in 17.7 to 23.7C water year-round.
A slim, cigar-shaped little fish around 12cm long, with a translucent silvery body and a distinct bright metallic stripe running along its flank from gills to tail. It swims in tight, loose-knit schools rather than alone, catching light so the whole group flashes silver as it turns. There's no strong colour contrast to look for beyond that lateral stripe, so body shape and schooling habit are your best clues underwater.
Divers typically encounter it moving in loose schools over reef and sand edges, likely feeding on the drifting plankton that gives schooling silversides their name. It shows little interest in divers and tends to keep its distance, parting around a diver rather than approaching. Look for the flash of its stripe catching the light as the school wheels and turns in open water near structure.
Like other atherinids, hardyheads school in numbers as a defence strategy, relying on synchronised, flashing movement to confuse predators rather than any individual camouflage or spines.
There isn't enough seasonal data to call a specific window, and the observed temperature range of 17.7 to 23.7C spans much of the year in Western Australian waters, so it's best treated as a year-round possibility rather than a seasonal target.
Reef neighbours a diver could mistake it for. Use the identification notes above to tell them apart.
Every logged sighting so far comes from Western Australia, making it the place to look for this species. Sites there report it as a rare find rather than a guaranteed encounter, so treat any sighting as a bonus rather than the main event of the dive.
Mapping where Hardyhead is logged…
Confirmed sightings so far come from Western Australia, where a handful of dive sites report it as a rare find. There isn't data yet from other countries or regions.
There's no clear seasonal pattern in the data, and it's been observed across a wide temperature range of 17.7 to 23.7C, so it's reasonable to look for it any time of year in Western Australian waters.
Look for a small, slender silver fish around 12cm long swimming in loose schools, with a bright metallic stripe running along its side. The stripe and the schooling habit are the two main giveaways.
They're a small species, typically reaching around 12cm in length, which is one reason they're easy to overlook among reef and sand habitats.
No, they pose no danger to divers at all. They're a small, harmless schooling fish that keeps its distance rather than interacting with divers.
Site and sighting data is aggregated from diver logs, iNaturalist and GBIF. For taxonomy and conservation status:
Anchovy
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